BRONX RIVER ALLIANCE CONSERVATION CREW
RAINWATER HARVEST SYSTEM INSTALLATION
By Frances Knickmeyer
Table of contents
1. Rainwater Harvest Training 101………...
2. How does it work? ....................................
3. Assessing potential installation sites…….
4. Creating a strategic plan for each site…...
5. Acquiring materials needed for the job…
6. Installation and Maintenance…………….
7. Conclusion……………………………….
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Rainwater Harvest Training 101
On February 25, 2009 the Bronx River Alliance, along with Lenny Librizzi and Lars Shellberg from the
Council on the Environment of NYC (CENYC), conducted a Rainwater Harvest Installation Training at
Williamsbridge Oval Park. The training involved individuals from Green Apple Corps, Youth Ministries
for Peace and Justice, Mosholu Preservation Corporation, and local homeowners. The training consisted
of the history and benefits of rainwater harvesting, materials required, and how to construct a rainwater
harvesting system.
A rainwater harvesting system consists of a series of gutters and pipes leading from the roof into a
rainwater barrel (also referred to as a water tank). This serves to capture runoff from the roof of a
building, which prevents it from falling to the pavement. There are two main reasons to install a
rainwater harvesting system.
1. Conserve drinking water, which is especially important in arid areas where water is limited.
a. This decreases the need to water lawns and gardens using water from the drinking water
supply.
2. Reduce the runoff created by a rainstorm. This is more important in urban areas with many
impervious surfaces.
a. By reducing runoff, the pollution that is usually carried by this water into the sewer
systems and then into lakes, rivers, and streams is diminished.
b. This also reduces the amount of water flowing directly into rivers thereby lessening
flooding.
How does it work?
A rainwater harvesting system captures the rain that falls onto a building roof before it flows to the
ground. Building gutters, which would normally carry water to downspouts, are instead connected to
pipes that lead to a rainwater barrel. The barrel collects water until it is full, at which point the excess
water is diverted into the overflow pipe. This pipe leads to a garden or other catchment system, or in
some cases, to the place where the outfall from the gutters was previously located. The barrel stores the
water until you are ready to use it.
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Assessing potential installation sites
During the assessment we found that each site was very different, and had its own unique requirements.
Our first installation was at a public site, French Charley Park House in the Bronx River Forest. At this
site, we had to install gutters, underground piping, and a platform for tank. Moreover, we planted a
rainwater garden adjacent to the rainwater barrel, to capture the overflow when the barrel is full. The
installations at private residences have had their own needs and requirements. These include keeping
windows clear and working around existing storage containers.
This 500-gallon watertank (located at the French Charley Park House) will
be used to water the rainwater garden (see below) naturally until
it is detached for the winter.
Rainwater garden.
Creating a strategic plan for each site
After assessing a site for its needs, a design is drawn up (see below) and a supply list is created. Each
design takes into account the amount of water coming off the building roof into the water tank. The
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amount of water is calculated using the area of the roof. Keep in mind, though, that the entire roof does
not have to drain into a single barrel, if it is not practical. If you do decide to drain the entire roof into
one barrel, the gutters may have to be re-done, so that they all flow to a single point. The amount of
water draining off the roof determines the size of the rainbarrel. The shape of the barrel (round or
rectangular, upright or horizontal) is determined by the size constraints at the site. For example,
windows can be a factor in determining whether to purchase an upright or horizontal tank. Other
structures such as support columns, containers, or trees can be determining factors in deciding on a
cylindrical or rectangular shape.
Wooden
platform on
which
rainwater
barrel will
sit
This is the plan the Bronx River Alliance Conservation Crew drew up
for the Mosholu Preservation Corporation site.
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Acquiring materials needed for the job
While the exact supplies for each site will differ, there are many similarities between sites. If there is not
an existing gutter system on the building, you will need to purchase the supplies necessary to install one.
Use the list below as to assist you with your project. (This supply list has been derived from our own
experience and from the “Rainwater Harvesting 101” guide developed by CENYC.)
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Rainwater barrel
o Determine the size needed using the roof area
Platform
o Use 4x4s OR for rainbarrels less than 55 gallons, you can use cinder blocks
o 6-inch spike nails (optional: use to build a platform out of 4x4s)
PVC piping
o Long, straight lengths
o 3-way connectors
o 4-way connectors
o 22-degree angles
o 45-degree angles
o 90-degree angles
o Male connectors
o Female connectors
o Cap to go over the PVC pipe into smaller cap to insert overflow
Other supplies
o Plunger (remove the handle)
o Hose bib (spigot)
o Hose bib adapter
o Tapcon screws use this type of screw to prevent water from leaking into the building)
o Plumbing strips (to secure the piping to the side of the building)
o Heavy duty strapping (to secure the tank)
o Lag bolts (3.5 inches x 6 inches length) (use to secure the strapping to the platform)
o PVC cleaner & glue
o Silicon sealant (Goop brand, water sealer)
o Handheld sealant
Tools
o Hole saw attachment or jigsaw
o Metal hacksaw
o Titanium drill bit
o Crimping tool
o PVC strap tightener
o Drill
o Hammer
o Screw drivers
o Level
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Installation and Maintenance
The installation of each project generally takes just one day.
1. To begin, the downspouts are detached from the gutters, and replaced with PVC piping to take
the rainwater into the barrel. Multiple lengths of PVC pipe will need to be attached together to
achieve the desired length and necessary angles, as the rainwater barrel cannot usually be placed
directly beneath the existing downspout.
2. Be sure to install all piping (including horizontal lengths) so that it is at a downward angle – no
more than a few degrees. A general rule of thumb is to angle the guttering or pipe ¼” downward
for every linear foot. This will ensure that the rainwater will flow into the barrel instead of sitting
in place. The PVC inflow pipe coming from the gutter system should be attached to the top of
the rainwater barrel. The overflow pipe, which will carry extra water into a rainwater garden or
other overflow catchment, should be attached near the top of the tank, but slightly below the
inflow pipe.
Gluing pipes together.
3. An additional diversion pipe is needed to bypass the rainbarrel entirely. This is used only during
the cold months, to prevent ice from forming. If ice were to form in the system it could expand
too much and create cracks and leaks, necessitating the replacement of many parts.
a. The diversion pipe should be installed between the gutter outflow and the barrel.
i. To install this pipe, you will need a four-way valve. Two ends (across from each
other) are used to connect the pipes leading to the water tank. One end will be
used to connect the diversion pipe. The other end will remain open. This will be
used to change the placement of the plunger.
1. The angle of the plunger determines where the water will head – toward
the tank in the warmer months or into the diversion pipe during the colder
months.
ii. The diversion pipe can be installed like a regular downspout – straight down – or
angled slightly out from the building to direct the water to a different location.
4. Frequently, a platform will need to be built to hold the rainwater barrel. The platform should be
built so that each layer is perpendicular to the layers above and below it.
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a. Depending on the site, the platform may need to be as little as eight inches high or a few
feet high. The platform enables you to attach a hose and drain the barrel. If the platform
is built higher, a watering can may be placed beneath the drainage spout.
b. The rainwater barrel should be secured to the platform and/or the building to be sure it is
not accidentally tipped over.
Attaching the 155-gallon rainbarrel to the rest of the system.
Close-up of the in-flow pipe attaching to the 155-gallon barrel (be sure to note
the slight downward angle), the bypass pipe, and the open connections where the
overflow pipe will be inserted.
There is very little maintenance involved with these systems.
1. To reduce algal growth in the water tank, a small amount of bleach can be added to the tank each
month, using the following table as a guide.
Tank Size
1000 gallons
750 gallons
500 gallons
50 gallons
Amount of Bleach
1/3 cup
1/4 cup
3 tablespoons
2 teaspoons
(This table is from the “Rainwater Harvesting 101” guide developed by CENYC.)
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2. Additionally, any accumulated debris needs to be cleared from the gutters.
a. We suggest doing this at least bi-weekly during the autumn, when the leaves are falling
off the trees. In areas with many trees around, the gutters may need to be cleaned more
frequently.
b. During other seasons, we suggest checking the gutters at least once a month.
3. Every so often, you need to go out during a heavy rainstorm and inspect the system for leaks.
4. In the late fall or winter (just before the first freeze) open all the valves, empty the barrel
completely, and rotate the plunger so it closes off the route to the tank.
5. In the spring, be sure to close all the valves and place the plunger so it closes off the bypass pipe.
Be sure to note, this water is for use on lawns and in gardens only. It is not for drinking! Each rainbarrel
should be labeled as such.
Conclusion
This article is intended to demonstrate the process needed to install a rainwater harvesting system, which
is a valued tool for water conservation and stormwater management. If you work in a step-by-step
fashion from the roof down, any complications can easily be overcome. We hope this guide encourages
you to install a system in your own backyard! Our installations ranged from 165- to 500-gallon tanks,
based on the roof size and anticipated water usage. The cost for these systems ranged from $554.18 for
the 165-gallon tank system at the LaJara House to $2,100.02 for the 500-gallon tank system at French
Charley Park House. Note that the cost of the 500-gallon system included the installation of gutters and
a rainwater garden. Rainwater harvesting systems are a great tool for collecting water for your gardens
and lawns, even during dry spells or droughts. Furthermore, you help out the environment at the same
time by reducing runoff pollution to local lakes, rivers, and streams.
Members of the Bronx River Alliance Crew, Lenny Librizzi of CENYC, and Henry
LaJara with the completed rainwater harvesting system at Mr. LaJara’s house.
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