There is a common thought that asphalt shingles should not be used
for rain collection due to leaching of contaminants into the water.
Almost any roofing material is suitable for rain catchment for
irrigation purposes. Asphalt shingles have, after proper filtration and
disinfection, even tested appropriate for
The most recent studies have
shown no appreciable difference among common roofing materials. In
2013 Rutgers tested rain barrel water quality for irrigation.
Results of this study showed that overall the
water quality of the rain barrel water was very good. Heavy metals were
well below federal irrigation standards for reclaimed water and posed
minimal risk for irrigating a vegetable garden. PAH's were not detected
in any samples. Results also showed the majority of water samples to be
below recommended irrigation guidelines for E. coli.
Link to referenced study
test of Rain Barrel water 2013
More studies can be found in the links section
Collected rain water is actually
high quality irrigation water
It is soft (slighty acidic), chlorine &
(unlike city water), and your garden actually benefits from the organic
debris that gathers
on your roof and enters your catchment system. This organic matter
breaks down and becomes liquid fertilizer for your plants. It's the
rain catchment version of compost tea.
irrigation is an ideal way to use collected rainwater,
drip tape and soaker hoses work well when the collected rainwater is
Rainwater collected in
rain barrels, or any other non-treated system is NOT intended for
potable use. This water can be used for irrigation, but should NOT
be applied directly to edible surfaces within a week of consumption.
Even though the UV rays of the sun
will eradicate any bacteria within
that time, it is always advisable to wash vegetables before
Catchment Systems for Garden and Greenhouse Irrigation ~ Rain Barrels ~
Stormwater Management ~ Native & Edible Garden Design
Habitat Creation ~ Rain Fed Gardens currently
offers design and installation services in eastern Pennsylvania, New
Jersey, southern New York, and the western half of Massachusetts