Water Conservation Opportunities for Individual Residences Serviced by On-Lot Wastewater Disposal Systems
Wastewater Sources and Average Flow Rates
- How is water used in a typical household?
- What amounts of water are involved in our normal daily activities?
- How much wastewater is produced by these activities
- How practical is water conservation for our household?
Answers to the above questions provide the basis for this fact sheet. Information presented is for illustrative purposes only and not to replace the guidance and regulatory specifications of the Pennsylvania Department of Environmental Protection.
Water used in a typical household
Typical rates of water use for various household devices and appliances are presented in Table 1.
|Device / Appliance||Units||Typical amount of water||Range|
|Automatic home type washing machine||gal/load||40||30-50|
|Automatic home type dishwasher||gal/load||6||4-5|
|Garbage disposal, home type unit||gal/person/day||2||1-3|
|Shower head, 5/8 in. 25-ft pressure||gal/min||25||23-28|
|Toilet, tank type||gal/use||5||4-6|
|Garden hose, 5/8 in. 25-ft pressure||gal/min||4||3-5|
Information from Tables 1 through 4 adapted from Criters, R.W. and G. Tchobanoglous, Small and Decentralized Wastewater Systems, W.C.B. McGraw-Hill, pages 169-183, 1998.
The amounts of internal water used as a percentage of the total for a private residence served by an on-lot wastewater disposal system is presented in Table 2.
|Use||Percent of total%|
|*Without water conservation devices|
|Kitchen food waste grinder||3||2-5|
Let’s take a typical amount of water used daily in a residence that is not conserving water as an example:
|Household activity||Water used
(with three people)
|Drinking and cooking
|Two toilet flushings
The amount of water used per day is the sum of household and personal activities. With three people, this amount is: (40 gal/residence/day) + (40 gal/person/day)(3 persons) = 160 gal/residence/day
Note that when overnight guests or older children are temporarily staying in the house, the extra bathing, toilet uses and loads of laundry will greatly add to the amount of wastewater.
The amounts of wastewater generated from several types of residences are presented in Table 3. These residences are served by a community or private water supply, a.k.a. “indoor plumbing,” where the wastewater amount is 60 to 80 percent of the water used, depending on the seasonal amounts used for landscaping needs outside of the residence.
|Type of residence||Wastewater, typical
|Trailer park home||40||30-50|
There are many factors to be considered when trying to get a good estimate of your wastewater flow. However, there are some rather straightforward ways of reducing residential water use as presented in Table 4. The water reductions that might be achieved are also provided.
|Flow-reduction devices||Volume used(gallons/person/day)||Water saved
|Before improvement||After improvement|
|* Assuming an eight-minute shower|
|Limiting flow shower head (3 gal/min)*||24||18||25|
|Limiting flow shower head (0.5 gal/min)||24||4||83|
|More expensive devices|
|Water efficient dishwasher||10||9||10|
|Water efficient clothes washer||25||23.5||6|
Using the information from Table 4 for water saving in bathing and toilet use alone shows that significant reduction can be achieved.
Putting Water Conservation into Practiceb
Let’s focus on a few simple steps that can reduce the amount of water used in a residence, and thereby decrease the amount of wastewater going to the on-lot system.
Search for and eliminate leaky fixtures in the plumbing system.
- Toilets – add food coloring into the water tank and check the toilet bowl in 15 minutes or so. If the bowl water has coloring, there is a leak.
- Faucets – if you have a leaky faucet, chances are great that you can correct the situation with a new low-cost washer.
Changes to the fixtures
There are some further changes you can make in the fixtures to reduce water use by buying new water-saving products when they become available.
There are a number of simple ways you and your family can reduce water use that require only a change in personal habits. For example, a 10-minute shower uses twice the amount of water as a 5-minute one. Don’t run the clothes washer and dishwasher unless they contain a full load. Other suggestions are:
- Wash vehicles using a bucket and sponge - not a hose.
- Do not let the water run while brushing your teeth.
- If you irrigate your garden, use drip irrigation.
- Use garbage-grinders sparingly.
- Collect roof runoff to water your garden.
If you are in the market for a new appliance, shop around and compare different models in terms of water use, electricity use, noise levels, etc. For example, invest in a front-loading clothes washer because they use less water than top-loading washers.
Prepared by Raymond W. Regan, Professor of Environmental Engineering and Albert R. Jarrett, Professor of Agricultural Engineering