Rain Barrels and Cisterns Rain Barrel SpecificationsHere are two
examples of rain barrel/roof top catchment systems. The first is of a
complex commercial system; the second, a home made design. Both achieve
the desired LID results of stormwater management.
The design of
any rain barrel is relatively simple, with its basic components
consisting of:
·
The actual barrel, often made of plastic, and recommended to be at
least 55 gallons. Most pre-manufactured barrels average about 60
gallons.
·A
sealed yet removal child resistant top to keep potential pests out,
but still allow easy access for cleaning. Screens, at the barrel
entrance are often included to reduce particulate matter and the
potential for mosquitoes.
·
Connections to the downspout, runoff pipe, and spigot.
A number of
accessories can be added to the basic barrel design and include:
·
Expanded storage volume, by connecting the barrels.
·A
water diversion soaker hose, to allow for the slow discharge of
water for a needed purpose such as lawn irrigation.
·An
automatic overflow so that water will not back up into the system.
·An
overflow irrigation design, as outlined below.
Commercial Rain Barrel Specifications
The figures
below exhibit
the typical components of a commercial rain barrel system. With
accessories, the cost can increase up to more than $200 per barrel (2002
year data).1
The Spigot
Irrigation System is a kit comprised of a standard hose fitting
on a 25' long, 3/4" poly-hose. The kit comes with a 1/16" drill bit
for creating holes in the hose where needed. The Overflow
Irrigation System is a kit that contains a single 50' long 3/4"
poly-hose, a T-connector, and the appropriate fittings and stainless
steel clamps. This system is fed by the 1.25" overflow outlet that
goes into a T-connector supplying two 25' long (or some combination
of the 50' of provided hose) hose sections that are able to then
distribute water through 1/16" holes. Detailed
specifications can be viewed at
http://www.composters.com/docs/rainbarrels.html#urb.
Homemade Rain Barrel Specifications
This rain barrel
system was put together for less than $20.2
Cisterns can
be constructed of nearly any impervious, water retaining material
and are distinguishable from rain barrels only by their larger sizes
and different shapes. They can be located either above or below
ground, and in out of the way places that can easily be incorporated
into a site design. Commercially available systems are typically
constructed of high density plastics. Cisterns can either be
constructed on-site or pre-manufactured and then placed on-site.
A simple
method of construction, sometimes still utilized in rural areas, is
to first lay a concrete floor in a small excavated area and then
cover the dirt walls with several coats of plaster to assure water
proofing. If the cistern is dug correctly its
round walls can then be capped with a
concrete lid.Small cisterns of up to 5000 gallon capacity
have been constructed in this manner.3
Materials
utilized for the construction of cisterns can include redwood,
polyethylene, fiberglass, metal, concrete, plaster
(on walls), ferro-cement and impervious rock such as slate and
granite. Typical components of a cistern roof top catchment system
include: the roof, gutters, and downspouts with connection to top of
cistern, and outflow connections for appropriate uses, i.e.,
irrigation.
Generally all
rainwater tank/cistern designs should include these components:
4
A solid secure cover
A leaf / mosquito screen at cistern
entrance
A coarse inlet filter with clean-out
valve
An overflow pipe
A manhole, sump, and drain to
facilitate cleaning
An extraction system that does not
contaminate the water (e.g. a tap or pump)
A soak-away to prevent spilled water
from forming puddles near the tank
Additional features might include:
A device to indicate the amount of
water in the tank
A sediment trap, tipping bucket, or
other "foul flush" mechanism
A lock on the tap
A second sub-surface tank to provide
water for livestock, etc.
