Additional information: The Septic Information Website
Home and Outdoor Living Water Requirements
Source: USDA "Water Systems Handbook." (Thanks to Keith Oberg, Professional
Home Inspection Service, Binghamton, NY, for providing this information.)
Table 1. Home and Outdoor Living Water Requirements
Use Flow Total
rate use
gpm US Gallons
Adult or child 50-100/day
baby 100/day
Automatic washer 5 30-50/load
Dishwasher 2 7-15/load
Garbage Disposer 3 4-6/day
Kitchen sink (a) 3 2-4/use
Shower or tub 5 25-60/use
Toilet flush 3 4-7/use
Bathroom lavatory sink 2 1-2/use
Water softener regeneration 5 50/100/cycle
Backwash filters 10 100-200/backwashing
Outside hose faucet 5 ?
(a) water flow restricting valves and shower heads can reduce flow and
water use by up to 50%.
Reverse Osmosis Systems - impact on septic systems and water use:
What about water volume from reverse osmosis water treatment systems? These can
vary by manufacturer with a range of 3:1 to 10:1 of waste to product efficiency.
"Typically" for every gallon produced with a top of the line system, 3 to 5
gallons goes into the septic tank. Less efficient systems (regardless of
shutoffs) can dump up to 10 gallons to waste for every gallon that goes into the
storage tank. Don't despair...the membranes of ten years ago dumped up to twenty
five gallons per gallon of product.
For concurrence: ask the manufacturer for their efficiency, platform statement,
and per cent recovery. An excellent resource for membrane information is the
National Sanitation Foundation. I am not confident about the generalized
information you obtain via EPA publications, Small Flows, etc. If you posture
your inquiries with the reputable manufacturers, you should be able to get
reliable flow information.
[Thanks to Larry Newcomb Encinitas Learning Center, jayhawk@cts.com, for the
above opinion--DJF]