Domestic water exiting a house is:
40-50% gray water, gray water is alkaline ph
50-60% black water
Subsurface irrigation saves 50% of irrigation from drying / evaporation
To grow food, the rain catchment surface must be 2.5 times larger than the cultivated area
Typical rain: 40% infiltrates, 15% goes to the watershed, 45% evapotranspires (becomes clouds again)
Rain falls ph 7, contact with carbon dioxide makes it slightly more acid to 5.7 ph, ponds are 8.0 ph. Concrete tanks & copper roofing make the water more acid. Below ph 7 copper pipe starts to etch & corrode. Add baking soda or a piece of limestone to make it buffered (more alkaline) .
Need gravity or pumps to provide 40 psi to 60 pst for a water tap/faucet
Remember air gaps to keep separate water systems from contaminating each other.
This article was written 09/30/2011