PRIVATE WATER SYSTEMS - Surface Waters - Catchment Areas
Catchment Areas
A catchment is a well defined area from which rainfall runoff
is collected. Catchment areas may be building roofs, paved areas, or
specially constructed areas covered with plastic or some other impervious
material.
Roofs
The type of roofing material affects the quality of water collected
from a roof. The most suitable roofing materials are galvanized steel and
aluminum. Consider the following before using a roof as a catchment surface:
Some roofing materials or roof coatings may be toxic. Contact local
health officials about toxicity of the materials to be considered for
use. Also, some paint and and some wood and asphalt shingles may
impart an objectionable taste to the water.
The air in some areas contains undesirable or harmful ingredients
that affect the quality of the water.
Rough surfaced roofing materials collect dirt and debris which
affect runoff.
Gutters and downspouts should be easy to clean and inspect.
Provide a roof area adequate to supply the amount of water needed.
Gutters
Installing gutter guards - 1/4 to 1/2 inch hardware cloth
screens - should keep leaves and twigs out of the water.
Roof washers are cheaper to construct and require less
service than sand, gravel, and charcoal filters. A roof washer traps
the first flow of dirty water off the roof. Provide a washer capacity
of about 10 gal for each 1000 square feet of catchment. A trickle
drain (1/8 inch hole) empties the barrel between rains.