1. home and garden

stormwater management for clean rivers
How to manage stormwater
Downspout
Disconnection
how to
disconnect downspouts
Portland gets an average of 37 inches of rain a year. Rain that runs off your
roof can flow directly into a sewer pipe, stream or groundwater. Why not put
it to better use? You can disconnect your downspouts to redirect water to
your yard or garden. Containing rainwater from hard surfaces on
your property also reduces demand on the sewer system and protects
the quality of rivers, streams, and groundwater.
What is involved in disconnecting
my downspouts?
You can disconnect your downspouts from existing
standpipes and let it flow over landscaped areas or
lawns. Disconnection can be a low-maintenance
option to help move water away from building
foundations and allow it to soak into the ground.
Disconnecting includes cutting the downspout;
attaching elbows, extensions, and splashblocks to
direct the water to flow away from the house;
plugging the standpipe; and securing the materials
to existing structures.
have disconnected downspouts to help reduce combined sewer overflows (CSOs) to the Columbia
Slough and Willamette River. See the resources section of this brochure for more information on this
special target area.
Where do I start?
Begin by preparing a good plan to ensure that the
stormwater soaks into the ground without damaging your structures or neighboring structures. This
brochure describes a simple, four-step process to
help you disconnect your downspouts.
Other brochures in this series show you How to
build a rain garden, soakage trench, or rain barrel,
to manage the stormwater runoff. Refer to the
resources section on page 7 to learn how
to get copies.
Are there incentives?
When you contain the rain on your property, you
qualify for a discount on the stormwater portion
of your city utility bill. See the resources section
of this brochure for more information on
Clean River Rewards.
If you live in the Downspout Disconnection
Program area, you can have your downspouts disconnected for free or you can earn $53 for each
downspout disconnected that meets the safety
considerations on page 3. Over 58,000 homeowners
STORMWATER MANAGEMENT
HOW TO - DISCONNECT DOWNSPOUTS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
observe your site
1
F
ind out where runoff from your downspouts
goes, including your house, garage, and other
covered surfaces. Are your downspouts draining
to your lawn or are they connected to the sewer
system or to drywells? Downspouts that drain into
standpipes (pipes) may drain into a public sewer system, a curb cut ( a hole in the curb at the sidewalk),
soakage trench, a drywell, or other stormwater
drainage system. If your downspouts drain into
soakage trenches or drywells on your property and
are in good working order, you do not need to disconnect, but may want to in order to avoid future
maintenance or replacement costs.
To find out if you have soakage trenches or
drywells, call 503-823-7660 for plumbing permits
or building records on file for your property.
Draw what you see
Sketch a site plan. You can print an aerial view
of your property from PortlandMaps.com as a
starting point.
Mark the locations of downspouts and roof line and
estimate the square footage of your roof area. Map
out areas in your yard down slope of structures
where you might disconnect downspouts.
example site plan: locate existing downspouts
downspouts k
STORMWATER MANAGEMENT
Safety considerations
Slope: Add or remove soil to make sure that
the slope of the ground allows water to flow
away from structures. However, do not disconnect downspouts on slopes over 10%.
Drainage: Avoid disconnecting downspouts in
an area too small for good drainage (see page
4 for guidelines).
Extensions: Disconnected downspouts must
be extended to discharge water at least 6 feet
from a structure’s basement and 2 feet from a
structure’s crawl space or slab foundation.
Downspout extensions and surrounding landscape surface must drain water away from
any structures.
Property Lines: The end of your downspout
extension must be at least 5 feet from your
neighbors’ property line and 3 feet from the
public sidewalk. You may need more room
if your yard slopes towards your neighbor or
the sidewalk.
Access: Avoid disconnecting downspouts or
adding downspout extensions across a walkway, patio, driveway, or in front of a gate
because of possible tripping hazards.
Other Hazards: Do not disconnect directly
over a septic system, drain field, or an underground oil tank unless they have been decommissioned. Do not disconnect within ten feet
of a retaining wall.
HOW TO - DISCONNECT DOWNSPOUTS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
3
2
design your disconnection
M
ark downspouts to be disconnected on
your existing site plan. Mark where you
might pitch gutters, move downspouts,
remove walkways or other impervious areas, or add
extensions or elbows to get around plants or other
obstructions.
Make sure you have enough landscaped area for
rain to soak safely into the ground. The ground
area must be at least 10% of the roof area that
drains to the disconnected downspout.
For example, to drain 500 square feet of rooftop,
there should be at least 50 square feet of landscape.
roof area
500 sq. ft.
sizing factor landscaped area size
x 10%
= 50 sq. ft. (or 5’ x 10’)
House 1,260 ft 2
All splashblocksdisconnect to lawn
Walk
Driveway
Move/rehang
downspout
to north corner
Garage
300 ft 2
You may have more than one option for directing
each downspout. Consider combining elbows and extensions to
send water to the side or front,
or to get around obstacles and
drain water away from the
house. Downspouts can also be
relocated along the gutter to a
safe drainage location.
4
STORMWATER MANAGEMENT
Tools
You will need
a hacksaw, a
drill, a pair of
needle-nose
pliers or
crimpers, a tape
measure, and a
screwdriver or nut driver.
Materials
Make a list of the parts and materials needed.
Downspout elbows and extensions come in a few
standard shapes, sizes, colors, and materials to fit
your gutters. Ask if the materials you choose can
be painted to match your paint color or blend into
your landscaping. Sewer standpipes must be sealed
with a rubber cap secured by a hose clamp or
with a wing-nut test plug. Most standpipes are
between three and five inches wide. Measure the
inside diameter of yours before shopping.
Some downspouts are attached only to the gutter
and the sewer standpipe. If so, you may need to
secure your downspout to your house with a bracket or strap to keep it in place when you disconnect.
Use durable, gutter-grade materials such as
aluminum, steel, copper, vinyl, and plastic.
Black ABS SCH 40 plastic is a durable option
found in most hardware stores and home
centers. Do NOT use
corrugated black plastic
(ADS), roll-out-hose,
PVC pipe, dryer hose,
swivel or open-trough
materials because of
their limited durability.
HOW TO - DISCONNECT DOWNSPOUTS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
Other suggestions
q Consider installing a hinged downspout elbow
and enclosed extension that you can flip up
against the house during dry weather or lawn
mowing. The extension must be enclosed, not
an open trough. (see diagram 1)
r Think about creating a space to disconnect
q
by removing paved surfaces, such as concrete
pathways, patios or unused driveway area.
s Replace pavement or concrete with pavers
or gravel where appropriate to allow for
infiltration. (see diagram 3)
t Extend downspouts underneath a deck or
raised patio to get runoff to a landscaped area.
(see diagram 4)
u Use plastic or concrete splashblocks, rocks,
flagstone, or boulders at the end of downspouts to control erosion, help direct runoff,
and add visual interest. (see diagram 5)
s
v Incorporate other stormwater management
systems into your downspout disconnections,
such as a rain garden, soakage trench, or
rainwater harvesting system. See the
resources section for more information.
t
u
STORMWATER MANAGEMENT
HOW TO - DISCONNECT DOWNSPOUTS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
5
A-B
3
disconnect
All disconnections should meet the safety considerations
found on page 3 and the water should flow away from
all structures.
A Measure the existing downspout from the top of
the standpipe and mark it at about 9 inches above
the standpipe. You may need to cut the downspout
higher depending on the length of your extension.
C
B Cut the existing downspout with a hacksaw at the
mark. Remove the cut piece.
C Plug or cap the standpipe using an in-pipe test
plug or an over-the-pipe cap secured by a hose clamp.
Do NOT use concrete to seal your standpipe.
plug with wing nut
cap with hose clamp
D
D Attach the elbow. Be sure to attach the elbow OVER
the downspout. Do NOT insert the elbow up inside
the downspout or it will leak. If the elbow does not
fit over the downspout, use crimpers or needle-nose
pliers to crimp the end of the cut downspout so it
slides INSIDE the elbow.
E Measure and cut the downspout extension to the
desired length. Attach the extension to the elbow by
slipping the extension OVER the end of the elbow.
Do NOT install the elbow over the extension or it will
leak. The length of the extension will depend on site
conditions and where you want the downspout to drain.
E
• Downspouts must drain at least 6 feet from
basement walls and at least 2 feet from crawl
spaces and concrete slabs.
• The end of the downspout must be at least 5 feet from
your property line, and possibly more if your yard slopes
toward your neighbor’s house.
F Secure the pieces with sheet metal screws at each joint
where the downspout, elbow, and extension connect.
It helps to pre-drill holes for the screws.
F-G
G Using a splash block at the end of the extension is
optional, but it will help prevent soil erosion.
Total distance will depend on whether
or not you have a basement.
6
STORMWATER MANAGEMENT
HOW TO - DISCONNECT DOWNSPOUTS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
maintenance
resources
Proper maintenance of your gutters, downspouts,
and landscaping can reduce problems.
Clean River Rewards
4
Gutters:
• Clean at least twice a year, and more often
if you have overhanging trees.
• Make sure gutters are pitched to direct
water to downspouts.
• Caulk leaks and holes.
• Make sure roof flashing directs water
into the gutters.
• Look for low spots or sagging areas
along the gutter line and repair
with spikes or place new hangers
as needed.
Downspouts:
• Check and clear elbows or bends in downspouts
to prevent clogging.
• Each elbow or section of the downspout should
funnel into the one below it. All parts should
be securely fastened together with sheet
metal screws.
Landscaping:
• The ground should slope away from structures.
• Don’t build up soil, bark dust, or woodpiles
against the siding.
• Avoid draining water onto impermeable
plastic weed block or cloth.
STORMWATER MANAGEMENT
Clean River Rewards is Portland’s stormwater discount program. When you contain the rain safely
on your property, you can save money with an ongoing discount on your city utility bill. Go to
www.CleanRiverRewards.com to register or to download publications to help you plan, build and maintain disconnected downspouts or other stormwater
management options. You can also find other technical assistance information and useful links. For more
information, call 503-823-1371.
Downspout Disconnection Program
The city offers free disconnection work for homes in
the Downspout Disconnection Program target area,
or homeowners in the target area can earn a onetime incentive of $53 per downspout disconnected
that meets the safety considerations on page 3.
For more program information call 503-823-5858 or
visit www.portlandonline.com/downspoutdisconnect.
Download all the How to brochures at
www.CleanRiverRewards.com
Additional Information
City of Portland Stormwater Management Manual:
www.portlandonline.com/bes/index.cfm?c=35117
City of Portland Stormwater
Solutions Handbook:
www.portlandonline.com/
bes/index.cfm?c=43110
HOW TO - DISCONNECT DOWNSPOUTS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
7
Environmental Services
Dan Saltzman, Commissioner
Dean Marriott, Director
1120 SW Fifth Avenue
Portland Oregon, 97204
503-823-7740
www.cleanriverspdx.org
Other publications in this brochure series:
How to manage stormwater - Rain Gardens
How to manage stormwater - Soakage Trenchs
How to manage stormwater - Rain Barrels
To help ensure equal access to city programs,
services, and activities, the city will reasonably
accommodate persons with disabilities.
Call 503-823-7740 or 1-800-735-2900 with
such requests. TDD 503-823-6868.
ES 0913
stormwater management for clean rivers
How to manage stormwater
Rain
Gardens
how to
build a residential rain garden
Portland gets an average of 37 inches of rain a year. Rain that runs off your
roof or patio can flow into a sewer pipe, stream or groundwater. Why not
put it to better use? You can create an attractive rain garden in your yard
that captures runoff and lets it to soak into the ground. Containing rainwater
from hard surfaces on your property also reduces wear and tear on the sewer
system and protects water quality in local streams and groundwater.
What is a rain garden?
Are there incentives?
A rain garden is a shallow depression that collects
rainwater and is often planted with native plants.
They can blend with your existing landscape, and
design can be formal or informal. A rain garden is
a great place to direct the water from disconnected
downspouts or paved areas, or to capture the overflow from a rainwater harvesting system.
A rain garden can save you money. When you
contain the rain on your property, you could
qualify for a discount on your city utility bill’s
on-site stormwater management fee.
Other brochures in this series show you How to
disconnect downspouts, build a soakage trench,
or rain barrel to manage the stormwater runoff.
Refer to the resources section on page 7 to
learn how to get copies.
How to begin
Start by learning about your site and preparing a
good plan to ensure that the plants in your rain
garden thrive and stormwater soaks into the
ground. This brochure describes an easy, four step
process to help you create your rain garden. See the
resources section for more information on managing stormwater safely on your property.
Why plant a rain garden?
When rain falls, it washes over roofs, driveways and
other impervious surfaces. If stormwater runoff
isn’t managed properly, it can wash dirt, oil and
chemicals into rivers, streams and groundwater.
A rain garden that filters pollutants as water soaks
into the ground also replenishes groundwater,
helps reduce flooding and erosion in streams, keeps
sewers from backing up into basements, and
reduces combined sewer overflows (CSOs). Rain
gardens can also provide habitat for birds,
butterflies, and beneficial insects, like bees.
STORMWATER MANAGEMENT
example site plan:
rain garden?
downspouts k
rain
garden?
HOW TO - RAIN GARDENS/SWALES
rain
garden?
rain garden?
CITY OF PORTLAND ENVIRONMENTAL SERVICES
1
observe your site
A
re your roof downspouts already disconnected to your lawn? Are they connected to the
sewer system or a drywell? Does your driveway runoff go into your yard or into the street?
Locate your rain garden where it will intercept and
collect the most runoff.
• Avoid building a rain garden in an area
that is too small for good drainage or too
close to a retaining wall.
Draw What You See
• A naturally low spot with good drainage is
ideal for a rain garden because water already
ends up there.
• Sketch a site plan. You can start by printing an
aerial view of your property from
www.portlandmaps.com.
• Mark the locations of downspouts and paved
areas. You can always move a downspout and
re-grade gutters so the rain drains to a suitable
location to build your rain garden, such as landscaped or lawn areas.
• Estimate the square footage of your roof area
and pavement that will drain to the rain garden.
• Map out where you might construct a rain garden. Choose spots that are down slope of the
downspouts or paved areas that will drain to the
rain garden.
Safety Considerations
• Call before you dig. Make sure you don’t damage underground utilities by digging a rain garden. Call 1-800-332-2344 to locate all underground utilities. The service is free.
• You may need to add or remove soil to make
sure that the slope of the ground allows water
to flow away from buildings, including your
house and garage.
• Disconnected downspouts must discharge water
at least six feet from a building’s basement and
two feet from a building’s crawl space or concrete slab foundation.
• Water in your rain garden must be at least five
feet away from neighboring properties and
three feet away from public sidewalks.
• Do not locate the rain garden over a septic system, drain field or underground oil tank unless
they have been decommissioned.
STORMWATER MANAGEMENT
Other Factors To Consider
• It’s easier to build a rain garden in a
relatively flat area.
• Avoid building a rain garden where water
ponds, because that indicates that soils
don’t drain well.
• Consider removing paved surfaces to create
space for a rain garden, or replacing pavement
or concrete with pavers or gravel where
appropriate.
• Avoid placing rain gardens underneath the
canopy of existing trees.
You do not need city permits to construct a
residential rain garden if:
• You don’t excavate or remove more than 10
cubic yards of dirt (that’s about enough to fill
one standard size dump truck);
• You don’t disturb over 500 square feet of
landscape area (about the size of a small two-car
garage);
• Your property has less than a 10% slope (see
“Measuring slope”);
• Your property is not within 50 feet of a wetland
or waterbody;
• Your property is not in a floodplain; or
• You do not install underground piping (such as
soakage trenches or French drains).
If any of these conditions do apply to your property, you may need to include additional options to
safely manage stormwater. See the brochures
resources section for more information on managing stormwater safely on your property.
HOW TO - RAIN GARDENS / SWALES
CITY OF PORTLAND ENVIRONMENTAL SERVICES
3
2
design your rain garden
A
Rain garden
for 2 Downspouts
dd your rain garden to your existing
site plan. Mark where you might move
downspouts, where stormwater comes
from and flows to, and where you might add
or move plants.
Make sure your rain garden is large enough to
drain the water directed to it within 36 hours. This
keeps water from stagnating and mosquitoes from
breeding. Size your rain garden to be at least 10%
of the area that drains to it.
* For example, if 500 square feet of rooftop drains
to your rain garden, the rain garden should be at
least 50 square feet.
roof area
500 sq. ft.
sizing factor
x 10%
rain garden size
= 50 sq. ft. (or 5’ x 10’)
If your soils drain slowly, your rain garden may
need to be larger.
Test Your Soils
Dig a hole two feet deep and two feet wide where
the deepest part of the rain garden will be. Fill the
hole with water and let it drain completely. Fill it
again and monitor how fast the water drains. If it
drains within 24 hours, this is a good spot to locate
a rain garden. It’s a good idea to dig a couple of
holes to see if drainage in your yard is uniform.
Sand, gravel or compost can improve drainage. Till
in a mix of two thirds sandy loam topsoil and one
third compost to improve conditions for plant
growth. Blend it well to a depth of 18 inches to
loosen compacted soil and allow plant roots to
establish more quickly.
Direct Water Away From Your House
An above-ground pipe is the easiest way to convey
water from your downspout to your rain garden.
Metal downspout material is durable and easy to
4
STORMWATER MANAGEMENT
Rain garden
for 3 Downspouts
House 1,260 ft 2
Walk
Driveway
splashblockdisconnects to lawn
Garage
300 ft 2
find at hardware stores. Make sure that materials
you use are sturdy and made for outdoor conditions (no dryer hose or indoor tubing). Suggested
materials include cast iron and Schedule 40 ABS or
PVC. If you are draining less than 1,500 square feet
of roof to your rain garden, you should use 3-inch
pipe. If you are draining more roof area, use 4-inch
pipe. You may want to:
• Direct the water into a shallow conveyance
swale (make sure the swale is lined if it’s close
to buildings);
• Build a rock-lined swale that looks like a dry
creek bed;
• Carve a channel in a piece of flagstone;
• Send water through a piece of bamboo into a
container or let it splash onto a rock; or
• Use a concrete or plastic splashblock.
Plan where the rain garden will overflow when it’s
full. Make sure excess water will flow away from
buildings and neighboring properties. You may
need to use additional stormwater management
options to handle the overflow or if you only have
a small area available for a rain garden. See this
brochures resources section for more information
on managing stormwater safely on your property.
HOW TO - RAIN GARDENS / SWALES
CITY OF PORTLAND ENVIRONMENTAL SERVICES
Plan in advance where the rain garden will overflow if it ever gets
completely full. Make sure excess water will flow away from buildings
and neighboring properties.
Choose Your Plant Palette
Plants are an important living feature of rain gardens. They filter
pollutants and keep soil in place. Plant root systems loosen soil
and improve drainage. They stimulate biological activity that
helps the soil break down pollutants and increase runoff infiltration
and retention. There are a wide variety of native plants that resist
disease and provide wildlife habitat. Many non-native
plants will also work well in your rain garden.
Choose plants suitable for the different water levels of your rain
garden. In the bottom two thirds, use plants like wetland rushes
and sedges that can tolerate lots of water. Upland plants that
need less water will do well in the upper one third. Dogwoods,
spirea and flowering currants are good choices. Keep in mind the
height and width of the plants when they mature when you
make your selections.
hardhack
rushes and sedges
Native plant nursery professionals or
garden clubs can help you choose
plants that are best suited for
your garden based on soil, sunlight
and your design. Take your
site sketch with you
when you purchase
your plants.
let rain splash onto
a boulder or
into group of
smaller rocks
build a rain garden
along the driveway
STORMWATER MANAGEMENT
HOW TO - RAIN GARDENS / SWALES
CITY OF PORTLAND ENVIRONMENTAL SERVICES
5
3
building it
Now you’re ready to start.
A Use string and stakes to outline the area you’re
going to dig.
B Moisten hard soils with a garden hose to make
digging easier. Dig up existing grass and plants.
Set aside any plants you might be able to
replant in the rain garden.
C Dig the entire rain garden about 18 inches deep
to loosen soil, then add a few inches of soil,
sloping the sides at about 20% (or at a ratio of
3:1) to reduce the risk of erosion and soil falling
back into the bottom of the rain garden.
D The minimum suggested depth of the finished
rain garden should be 6 to 12 inches. The deepest part of your rain gaden should be furthest
from buildings, a suggested ten foot distance.
Measuring a slope
Tie a level string from a stake pounded into the
ground at an uphill spot to a stake pounded into the
ground downhill. Measure the distance between the
stakes (width) and from the string to the ground at
the downhill stake to the ground (height). Divide
the height by the width to get the slope in decimal
format. Multiply this by 100 to obtain the percent.
example drawing:
uphill
stake
downhill
stake
width
string
height
E Plant your rain garden. Use a variety of species
and plant densely to make it harder for weeds
to take root and to reduce soil erosion. After
planting, add some compost to prevent erosion
and provide nutrients to plants. Consider
using weed-free straw for soil cover during
the first winter.
If the width is 10 feet and height is 6 inches, then
your slope is 5%.
F Disconnect your downspouts. After the plants
are established in a few months, disconnect your
downspouts to water your new rain garden.
• If the garden is on a slight slope, add a berm
on the downhill slope to hold in rainwater.
6
STORMWATER MANAGEMENT
Height
Width
6 inches (0.5 feet) ÷ 10 feet= 0.05
percentage
x 100
Slope
5%
• Make the main basin of the garden as level
as possible so that water spreads evenly.
• Use plastic or concrete splashblocks, rocks
or boulders at the end of
downspouts to control
erosion and add
visual interest.
HOW TO - RAIN GARDENS / SWALES
CITY OF PORTLAND ENVIRONMENTAL SERVICES
4
maintenance
M
aintain your rain garden regularly as you
would with any other kind of garden.
After the garden is established in one to
three years, maintenance should be minimal.
Inspect your rain garden periodically, especially
after a heavy rain.
• Irrigate deeply once a week during dry months
to encourage root growth and keep plants
strong, especially while plants are getting
established.
• Avoid chemical weed killers or fertilizers in
stormwater management facilities. Pull
weeds by hand before they become
established.
• Remove sediment and debris,
watch for erosion, and replace
plants as needed.
resources
Clean River Rewards
Clean River Rewards is Portland’s stormwater
discount program. When you contain the rain
safely on your property, you qualify for an on-site
stormwater management charge discount on your
city utility bill. Go to www.CleanRiverRewards.com
or call 503-823-1371 for more information.
At www.CleanRiverRewards.com, you can download
publications to help you plan, build and maintain
your stormwater management options, and find
other technical assistance information and useful links.
Download all the How to brochures at
www.CleanRiverRewards.com
More Resources
• Add compost or mulch two to
three inches deep once a year to
boost stormwater infiltration
and feed the plants.
Be Flexible
If a plant isn’t thriving where you first placed it,
move it to another part of the rain garden. Some
areas in a rain garden will be wetter or drier than
others. Sometimes it isn’t easy to tell where a plant
will grow best until it’s rained a few times. A rain
garden is a living system, so go with the flow.
Harvesting The Rain in
the Pacific Northwest: Rain Gardens
http://clark.wsu.edu/volunteer/ws/ws-raingardens.pdf
Rain Garden Network
www.raingardennetwork.com/
East Multnomah Soil and Water Conservation District
http://emswcd/raingarden
Rain Garden Examples
For inspiration, check out these beautiful rain gardens:
• Glencoe Elementary School, 825 SE 51st Avenue
• Mt. Tabor Elementary School, 5800 SE Ash
• Hayhurst Elementary School, 5037 SW Iowa
• Astor Elementary School, 5601 N Yale
• Whitaker Ponds, 7040 NE 47th Avenue
• East Multnomah Soil and Water Conservation
District, 5211 N Williams Avenue
Walk through your neighborhood. You may be
surprised at the number of yards that already have
something similar. Ask neighbors about their rain
gardens to see what worked for them.
STORMWATER MANAGEMENT
HOW TO - RAIN GARDENS / SWALES
CITY OF PORTLAND ENVIRONMENTAL SERVICES
7
Environmental Services
Dan Saltzman, Commissioner
Dean Marriott, Director
1120 SW Fifth Avenue
Portland Oregon, 97204
503-823-7740
www.cleanriverspdx.org
Other publications in this brochure series:
How to manage stormwater - Downspout Disconnection
How to manage stormwater - Soakage Trenchs
How to manage stormwater - Rain Barrels
To help ensure equal access to city programs,
services, and activities, the city will reasonably
accommodate persons with disabilities.
Call 503-823-7740 or 1-800-735-2900 with
such requests. TDD 503-823-6868.
ES 0902 REVISED FEB 09
stormwater management for clean rivers
How to manage stormwater
Rain
Barrels
how to
build your rain barrel
Portland gets an average of 37 inches of rain a year. Rain that runs off
your roof can flow into a sewer pipe, stream or groundwater. Why not
put it to another use? A rain barrel can capture some of that rainfall for
later use on your property. Capturing and reusing rainwater from your
roof surfaces also reduces demand on the sewer system and
protects the quality of streams and groundwater.
What is a rain barrel?
A rain barrel is a simple rainwater collector that
captures and stores a portion of the runoff from a
roof downspout for non-potable, exterior uses,
such as irrigation. Rain barrels
come in a wide variety of materials, designs, and colors. Common
sizes for residential use are 55
gallons and 90 gallons. They are
usually installed on the ground
next to buildings.
A rain barrel is not a stormwater
disposal method, but is a way to
capture a small fraction of the
rainwater that flows off your
roof. The rest of the runoff will
still need to go to an approved
stormwater discharge location.
Are there incentives to installing
a rain barrel?
Using rain barrels to temporarily store and reuse
rainwater can conserve drinking water by providing
a water source for gardens. This
can also reduce both the water
use charge and corresponding
sewer charge on your city utility
bill.
If used with an approved location
where overflow water soaks into
the ground, you can qualify for
other City of Portland financial
incentives. All city ratepayers can
qualify for a discount on the
on-site stormwater portion of
their city utility bill. If you live in
the Downspout Disconnection Program area, you
also may be able to earn a one-time incentive of $53
for each downspout that is safely disconnected. By
2007, over 55,000 homeowners had safely disconnected downspouts to help reduce combined sewer
overflows (CSOs) to the Columbia Slough and
Willamette River.
See the Resources section of this brochure
for more information.
STORMWATER MANAGEMENT
HOW TO - RAIN BARRELS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
1
observe your site
To determine if a rain barrel is right for your
property, the first step is to identify your sites
drainage conditions. Answer the questions below
as you walk around your property.
Where does the runoff from your
roof area go now?
example site plan: locate existing downspouts
Sketch a site plan. You can print an aerial view of
your property from PortlandMaps.com as a starting point. Mark the locations of downspouts and
roof lines, estimate the square footage of your
roof and paved areas, and map where all these
areas drain.
rain barrel?
downspouts k
Where would you like to locate
your rain barrel?
Install your rain barrel based on where you will
use the water in your yard. Keep in mind that it
may be possible to rehang the gutter and move
the downspout to a more desirable location. The
rain barrel must be located at the base of one of
the downspouts draining your roof gutter. This is
the downspout you will work with.
Where does that downspout
currently drain?
The downspout you will divert to your rain barrel
probably drains into a standpipe or to your yard.
This is the stormwater discharge point and is the
same location where the rain barrel should overflow to.. If you wish to change your stormwater
discharge point, please refer to step 2.
STORMWATER MANAGEMENT
HOW TO - RAIN BARRELS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
3
2
plan your rain barrel
Rainwater collection for residential, external, nonpotable uses such as irrigation, do not require a
city permit, but there are still design considerations to follow.
Overflow
All rainwater collection systems must have an
overflow to a safe disposal location. The average
residential roof generates about 30,000 gallons of
rainfall runoff every year, and an average 55 gallon rain barrel captures only a fraction of that.
Even if you have multiple rain barrels, you must
have an overflow to a safe discharge location.
If your rain barrel overflows into the standpipe,
be sure the overflow pipe is attached and sealed
to the standpipe opening.
If the downspout to be connected to your rain
barrel currently drains to a surface infiltration
area in your yard, the overflow from your rain
barrel should also discharge to that location.
If the downspout currently drains to a standpipe
and you wish to change your overflow disposal to
surface infiltration in your yard, you must meet
the safety guidelines detailed in How to Manage
Stormwater- Downspout Disconnection or the
How to Manage Stormwater- Rain Gardens guide
(see Resources section of this document).
Safety Considerations
• The barrel must have a lid and a sturdy fine
mesh covering all openings to prevent mosquitoes and debris from getting inside.
• The water from the rain barrel should never
be used for drinking, cooking or other potable
uses.
• Your rain barrel must have an overflow to a safe
discharge point.
• If you use a moss-control product on your roof,
be sure to use a product that is garden-safe.
Larger or more complex systems
More complex rainwater collection systems have a
much larger storage container (a cistern), and/or
use pumps to move water to desired locations.
Some use their captured rain water indoors for
toilet flushing. These projects involve factors not
applicable to simple rain barrels, such as plumbing
and electrical work, soil excavation, or concrete
foundations and other structural components. For
rainwater collection projects of this scale, you
should consult a professional to review design, construction, and safety considerations.
For more information about residential or commercial rainwater re-use and potential permit requirements, see the Portland Rainwater Harvesting Code
Guide or contact the Bureau of Development
Services at 503-823-7300.
• Your rain barrel must be secured on a firm, level
surface. A full 55-gallon rain barrel weighs over
400 lbs. and tipping is a risk if it’s unsecured or
on uneven ground.
• The barrel must be structurally sound and
should be a food-grade container made to
hold liquid. Containers such as trash cans
are not designed to withstand the pressure
of the water.
4
STORMWATER MANAGEMENT
HOW TO - RAIN BARRELS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
3
construction
Many nurseries and yard supply stores sell fully assembled
rain barrels, but you can get an unmodified barrel and
convert it into a rain barrel yourself. Assemble your tools
and supplies then follow the construction steps illustrated
on the following page.
Tools
If you build your own rain barrel:
• drill
• inch hole saw for overflow pipe
• one-inch spade bit for spigot
• tin snips or heavy-duty scissors for cutting screen
• adjustable wrench
• utility knife
• safety glasses
Materials
• One 55 to 90-gallon food grade plastic
barrel (can be found online or at local
restaurant suppliers, nurseries, or
gardening supply stores)
Find the following items at most plumbing
or hardware stores:
• hose spigot with 3/4 inch threaded inlet
and 3/4 inch male hose end
• two 3/4 inch galvanized locknuts to secure
spigot from the inside of the barrel
To disconnect your downspout to
your rain barrel:
• hacksaw
• drill
• tape measure
• screwdriver or nut driver
• pliers or crimpers
• four 1-inch (opening) washers to provide
rigid surface to fasten hose bib
• Teflon tape
• silicon adhesive or outdoor caulking
• two 8”x 8” x 12” concrete or wooden blocks
• window screen mesh (enough to cover the
barrel opening)
• downspout elbow to route the downspout to
the barrel
• clincher strap (attaches downspout and
barrel to house)
• small pieces of wood blocking to use behind
clincher strap (if necessary)
• any additional materials necessary for
the overflow location
• 1/4” #6 sheet metal screws for downspout
• 3/4” screws for clincher strap
• 2” overflow pipe fittings
STORMWATER MANAGEMENT
HOW TO - RAIN BARRELS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
5
Construction in 6 Easy Steps
1
Inlet: Create an opening with fine screening through which the rain
barrel will collect water from the downspout elbow. This can be a single screened opening large enough to accommodate the downspout
elbow (as shown in the photo), or a series of smaller screened openings
directly in the top of the barrel.
2
Overflow: Drill a hole near the top of the barrel to accommodate an
overflow pipe that is at least 2 inches in diameter. If the overflow pipe
elbow seals and seats securely, it can be threaded directly into the barrel
opening. If not, it should be secured with washers on both sides of the
barrel and a nut on the inside. Use Teflon tape around the threads and a
bead of silicon caulking around the opening to ensure a tight seal.
3
Foundation: Create a raised, stable, level base (like concrete blocks) for
the rain barrel to sit on. You might want to test stability by filling the
rain barrel with water before attaching to your structure. A full rain
barrel is very heavy and tipping is a risk if it’s unsecured or on
an uneven surface.
4
Downspout: Cut the downspout with a hacksaw so that the elbow will
sit just above the rain barrel inlet. Attach the elbow over the downspout
with a screw and secure the downspout to the house with the strap.
Attach Barrel: Set up the barrel beneath the elbow and secure the barrel to the house with a strap. Cut and attach the overflow pipe to the
overflow elbow and direct to the existing discharge location.
6
STORMWATER MANAGEMENT
5
Outlet: Drill a hole near the bottom of the empty barrel to attach the
drain spigot. If the spigot seals and seats securely, it can be threaded
directly into the barrel opening. If not, it should be secured with
washers on both sides of the barrel and a nut on the inside. Use Teflon
tape around the threads and a bead of silicon caulking around the
opening to ensure a tight seal.
6
Use: After a rainfall, fill a watering can using the bottom spigot or
attach a hose to use the water where it’s needed.
HOW TO - RAIN BARRELS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
maintenance
resources
Simple maintenance of your stormwater system can prevent problems.
Clean River Rewards
4
• Clean gutters at least twice a year, more often
if you have trees.
• Make sure gutters are tilted to direct
water to downspouts and fix low
spots or sagging areas along the gutter line with spikes or place new
hangers as needed.
• Make sure roof flashing directs water
into the gutter.
• Make sure all parts are securely fastened together and the rain barrel
is securely
fastened to the building.
• Clean out the rain barrel and check for leaks at
least once a year. Check and clear downspout
elbows, rain barrel screening, and overflow to
prevent clogging. Caulk any gutter, downspout, barrel, and overflow leaks and holes.
• Make sure the rain barrel remains securely
screened to prevent mosquito entry.
• If overflow is to a surface infiltration area,
monitor the overflow area and regrade soil if
necessary to make sure water drains away from
structures and does not flow onto pavement,
sidewalks, or neighboring properties.
Clean River Rewards is Portland’s stormwater discount program. When you contain the rain safely
on your property, you can save money with an
ongoing discount on your city utility bill. Go to
www.CleanRiverRewards.com to register or to
download publications to help you plan, build
and maintain your stormwater management
options. You can also find other technical
assistance information and useful links. For more
information, call 503-823-1371.
Downspout Disconnection Program
The city offers free disconnection for homes in
the Downspout Disconnection Program target
area. Homeowners in the target area who do the
work themselves can earn a one-time incentive
of $53 for each downspout safely disconnected.
Call 503-823-5858 or go to
www.portlandonline.com/downspoutdisconnect
for more information.
Additional Information
City of Portland Stormwater
Management Manual
www.portlandonline.com/bes/index.cfm?c=35117
City of Portland Stormwater
Solutions Handbook
www.portlandonline.com/bes/index.cfm?c=43110
Portland Residential Rainwater Harvesting
Code Guide
www.opdr.ci.portland.or.us/pubs/CodeGuides/Cab
o/RES34%201.pdf
City of Portland Office of Sustainable
Development www.portlandonline.com/osd
See the back cover for other ‘How to’
brochures in this series
STORMWATER MANAGEMENT
Bureau of Development Services Records and
Research 503-823-7660
HOW TO - RAIN BARRELS
CITY OF PORTLAND ENVIRONMENTAL SERVICES
7
Environmental Services
Dan Saltzman, Commissioner
Dean Marriott, Director
1120 SW Fifth Avenue
Portland Oregon, 97204
503-823-7740
www.cleanriverspdx.org
Other publications in this series:
How to manage stormwater - Soakage Trenches
How to manage stormwater - Rain Gardens
How to manage stormwater - Downspout Disconnection
To help ensure equal access to city programs,
services and activities, the city will reasonably
accommodate persons with disabilities.
Call 503-823-7740 or 1-800-735-2900 with
such requests. TDD 503-823-6868.
ES 0911 Ju ne 2009
stormwater management for clean rivers
How to manage stormwater
Soakage
Trenches
how to
build a residential soakage trench
Portland gets an average of 37 inches of rain a year. Rain that runs off your
roof or patio can flow into a sewer pipe or stream. Why not put it to better
use? You can create a soakage trench in your yard that captures runoff and
lets it to soak into the ground. Containing rainwater from hard surfaces
on your property also reduces wear and tear on the sewer system
and protects water quality in local streams and groundwater.
What is a soakage trench?
A soakage trench, or infiltration trench, is a
below ground shallow, linear trench filled
with gravel under an underground
perforated pipe.
Soakage trenches can help create borders
or edges to your existing landscaping, or
be completely underground and invisible.
You can also use them to capture the
overflow from rain gardens or rainwater
harvesting systems.
Other brochures in this series show you
How to disconnect downspouts, build a
rain garden, or rain barrel to manage the
stormwater runoff. Refer to the resources
section on page 7 to learn how
to get copies.
Are there incentives to
build a soakage trench?
When rain fall, it washes over roofs, driveways and
other impervious surfaces. If stormwater runoff isn’t
managed properly, it can wash dirt, oil and chemicals into
rivers, streams and groundwater.
Where do I begin?
Prepare a good plan to ensure that the stormwater soaks into the
ground without damaging your building or neighboring buildings.
This brochure describes an easy, four-step process to help you
create your soakage trench.
STORMWATER MANAGEMENT
HOW TO - SOAKAGE TRENCH
CITY OF PORTLAND ENVIRONMENTAL SERVICES
1
observe your site
W
atch where runoff from your roof downspouts, patios, and driveways goes. Are
your downspouts disconnected to your
lawn or are they still connected to the sewer system? Does your driveway runoff go into your yard
or the street? Locate your soakage trench where it
will safely intercept and collect the most runoff
from downspouts and drains.
Draw What You See
• Sketch a site plan. You can print an aerial view of
your property from www.portlandmaps.com as a
starting point.
You need a city plumbing permit to
construct a residential soakage trench.
Information about permits is available at
www.portlandonline.com/bds. See the
brochure resources section for more
information.
Soakage trenches may not be appropriate for all
sites. If your site has the following conditions, a
soakage trench may not be suitable:
• Your property has slopes greater than 20%;
• Your property is within 50 feet of a wetland or
waterbody; or
• Mark the locations of downspouts and paved
areas. You can always move a downspout and regrade gutters so that the rain drains to a suitable
location for your soakage trench.
• Your property is in a floodplain.
• Estimate the square footage of your roof area
that drains to each downspout.
If any of these conditions apply to your property,
you may need to include additional options to safely manage stormwater. See this brouchure resources
section for more information.
• Map out areas in your yard down-slope of
buildings where you might construct a
soakage trench.
• The trench needs to be installed level and parallel to the contour of the finished grade.
• Your property has high groundwater, seeps
or springs.
example site plan:
Safety Considerations
Because soakage trenches are underground,
it’s important to make sure they don’t affect your
or your neighbors’ property. Soakage trenches
should be:
• At least 10 feet away from buildings;
downspouts k
soakage trench?
soakage trench?
• At least 5 feet away from all property lines;
• At least 5 feet away from all utility lines.
• Not within 20 feet of a septic system or drain
field, or above an underground oil tank that
hasn’t been decommissioned.
• Call before you dig. Make sure you don’t damage underground utilities by digging a trench.
Call 1-800-332-2344 to locate all underground
utilities. The service is free.
STORMWATER MANAGEMENT
HOW TO - SOAKAGE TRENCH
CITY OF PORTLAND ENVIRONMENTAL SERVICES
3
2
design your soakage trench
Mark the location of your soakage trench on
your site plan.
roof area
sizing factor
750 sq. feet
Calculate how large your soakage trench
needs to be.
• On the east side of the Willamette River where
soils generally drain well, the soakage trench
needs to be 20 linear feet for every 1,000 square
feet of impervious area draining to it (sizing
factor of 0.020).
• On the west side of the Willamette River where
soils generally don’t drain as well, the soakage
trench needs to be 30 linear feet for every 1,000
square feet of impervious area (sizing factor of
0.030). Regardless of where you live, if your soils
don’t drain well, use the west side sizing factor.
x
0.020
soakage trench length
=
15 feet long
For example, for a house in Southeast Portland
with well-draining soils and 750 square feet of
rooftop to be managed, the soakage trench
should be 15 feet long.
Test Your Soils
Dig a hole two feet wide and two feet deep
where you want to locate your soakage trench.
Fill the hole with water and let it drain completely. Fill it again and monitor how fast the water
drains. If it drains within 24 hours (approximately
1” per hour), this may be a good spot to locate a
soakage trench. It’s a good idea to dig a couple of
holes to see if drainage in your yard is uniform.
Soakage trench length is determined by the total square
footage of the area served, with a 10 ft length minimum.
minimum 10 ft
from structure
min. 1 ft
to top of
pipe
east - 30”
west - 36”
leaf trap
(optional)
finished grade
minimum 1 ft
from top of pipe
silt trap
(optional)
conveyance pipe
should tilt down
slightly
4
filter fabric covers
rock and pipe
east - 18”
west -12”
minimum
10 ft length
perforated pipe *
unshielded rubber coupling
solid conveyance pipe
(1/4” slope per foot
toward trench)
STORMWATER MANAGEMENT
trench filled with 3/4 -2 1/2” clean rock
HOW TO - SOAKAGE TRENCH
*(install level and parallel to
contour of finished grade)
CITY OF PORTLAND ENVIRONMENTAL SERVICES
Direct Water Away From Your House
Locate your soakage trench where water from
your downspouts or rainwater harvesting system
will drain into it, at a low
point in your yard and
downslope from building
foundations. Make sure that
materials you use are sturdy
and made to handle outdoor
conditions. Suggested pipe
materials include cast iron, or
Schedule 40 ABS or PVC pipe.
Ask your local hardware store
for these kinds of supplies. If
you are draining less than
1,500 square feet of roof to
your soakage trench, you
should use 3” pipe. If you are
draining more roof area, use
4” pipe.
Your Permit
example site plan
Once you’ve located your soakage trench, you
will need to apply for a city plumbing permit
before you start digging. Bring a clear copy of
your site plan to the city’s Development Services
Center. The plan should show where you want to
locate your soakage trench, including distances to
buildings, property lines, and other structures.
The plan should show your pipe size, length
and material.
PROPERTY LINE
5 ft
24 lf.
trench
8 ft
3” ABS
pipek
10 ft
10 ft
Building with
basement and
1000 ft2
of roof area
draining to the
soakage trench
Garage
driveway
walk
street name
STORMWATER MANAGEMENT
HOW TO - SOAKAGE TRENCH
CITY OF PORTLAND ENVIRONMENTAL SERVICES
5
3
building it
Step by Step
Direct Runoff to the Trench
A Use string and stakes to outline the
area you’re going to dig.
Disconnect your downspouts or connect your
rainwater harvesting system to your soakage
trench with a solid conveyance pipe. Install the
pipe at a slope of at least 1/4” per foot to
allow the rainwater to drain to the soakage
trench. Locate the pipe 12” underneath the
surface of your yard.
B Dig up existing grass an plants.
Set aside any shallow-rooted
plants you might be able to
replant above your soakage trench.
C East side of the Willamette River: dig a trench
at least 34” deep and 30” wide.
West side of the Willamette: dig a trench at
least 28” deep and 36” wide.
Consider installing a y-junction standpipe
cleanout to filter out debris. Another option is
to install a silt basin or washer between the
rainwater source and the soakage trench to
trap debris and allow for cleanout.
D Line the bottom and sides of the trench with
filter fabric. Use filter fabric 8’ wide and the
length of your trench.
E East side soakage trenches: fill the trench
with 18” of clean, 3/4” to 2.5” drain rock.
Get It Inspected
Call the City of Portland to inspect your work
prior to covering your pipe. The instructions
that you got with your plumbing permit
walks you through the inspection request
process. If there are any concerns about your
construction, the inspector will tell you what
to do in order to pass the next time you
request inspection.
West side trenches: fill the trench with
12” of clean, 3/4” to 2.5” drain rock.
F Fold one side of the filter fabric over the sand
or small rock.
G Place the perforated pipe as level as possible on
top of the drain rock. Cap the down slope end
of the perforated pipe.
Cover It
H Fold the other side of the filter fabric over the
perforated pipe.
Following a successful inspection, cover the
soakage trench with the original soil from the
trench or with gravel. There
should be about 12” of soil or
West Side
gravel covering the perforated
specs
pipe and the surface of your
yard. You can cover the soakage
12” min
trench with grass, small shrubs,
rock or gravel.
Soakage Trench: construction detail
filter fabric to be
placed on sides and ends
of trench
East Side
specs
12” min
40”
ROCK
18”
add rock and fold
one side of fabric
over rock
place perforated
pipe
in center
and cover all
with remaining
side of fabric
green tracer wire
on pipe
24”
ROCK
12”
36”
30”
6
STORMWATER MANAGEMENT
HOW TO - SOAKAGE TRENCH
CITY OF PORTLAND ENVIRONMENTAL SERVICES
4
maintenance
C
leaning and maintaining your downspouts
and gutters keeps leaves and debris from
clogging your soakage trench.
• Tree roots can damage subsurface systems and
pipes, so avoid planting tress over or near the
soakage trench.
• Some moss cleaners contain pesticides, which
can harm soil microbes that filter
and break down pollutants. Use
earth-friendly moss
cleaners or scrub moss off roofs.
• Clean out the leaf trap or silt
basin on a regular basis. Organic
material (dirt, leaves) can be
composted or used in your yard.
resources
Clean River Rewards
Clean River Rewards is Portland’s stormwater
discount program. When you contain the rain
safely on your property, you qualify for an on-site
stormwater management charge discount on your
city utility bill. Go to www.CleanRiverRewards.com
or call 503-823-1371 for more information.
At the Clean River Rewards website, you can also
download publications to help you plan, build and
maintain your soakage trench including a referral list
of design professionals and contractors, technical
information, and links to other programs, such
as Naturescaping. Download all the How to brochures
at www.CleanRiverRewards.com.
More Resources
City of Portland Development Services
www.portlandonline.com/bds
Visit the Development Services Center (DSC) at
1900 SW 4th Avenue, or call 503-823-7300.
The DSC is open Monday through Friday,
7:30 am - 3:00 pm, and there is an evening permit
night on Thursdays, from 5:00 pm to 7:30 pm.
City of Portland Residential Plumbing Permits:
www.portlandonline.com/bds/index.cfm?c=41036
City of Portland Stormwater Management Manual:
www.portlandonline.com/bes/2008SWMM
City of Portland Stormwater Solutions Handbook:
www.portlandonline.com/bes/stormwatersolutions
STORMWATER MANAGEMENT
HOW TO - SOAKAGE TRENCH
CITY OF PORTLAND ENVIRONMENTAL SERVICES
7
Environmental Services
Dan Saltman, Commissioner
Dean Marriott, Director
1120 SW Fifth Avenue
Portland Oregon, 97204
503-823-7740
www.cleanriverspdx.org
Other publications in this brochure series:
How to manage stormwater - Rain Gardens
How to manage stormwater - Downspout Disconnection
How to manage stormwater - Rain Barrels
To help ensure equal access to city programs,
services, and activities, the city will reasonably
accommodate persons with disabilities.
Call 503-823-7740 or 1-800-735-2900 with
such requests. TDD 503-823-6868.
ES 0912 June 2009