Photograph of huge water tanks at an old property with a well having a slow recovery rate. Home & Outdoor Living Water Quantity Requirements
     


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This article outlines typical daily residential water usage in gallons for people, appliances, and activities. This permits estimation of wastewater volume (for septic tank size determination) as well as water and well flow requirements and assists in water pump capacity or sizing specificatsions. Flow rates for common household plumbing fixtures and appliances is given as well as estimates of peak demand water usage rates for residential buildings.

This data is also useful when evaluating adequacy of private well and water supply quantity, well flow rate, and wastewater loads on onsite residential septic systems. Daily wastewater volume to be treated and disposed-of at a site determines the design parameters for onsite wastewater treatment or septic systems as well as suggesting choices among alternative septic designs and septic products.

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Home and Outdoor Living Water Requirements, Plumbing Fixture and Appliance Water Flow Rates

How much water does a family use each day? What is the water flow rate for common household fixtures and appliances? How is this data used?

Article contents:

  • How to estimate water quantity usage in order to estimate water supply needs & water pump capacity needed
  • How to estimate septic tank size and system capacity needs based on daily wastewater flow
  • List of articles giving options for increasing the quantity of water available at a site:
  • Well water problems: running out of water, options list

The following table lists water usage requirements and typical fixture flow rates or device flow rates for home and outdoor living in the U.S.

Table 1. Home and Outdoor Living Water Requirements
Typical Plumbing Fixture Water Usage & Flow Rates

Use Flow Rate
GPM
Total Use - U.S. Gals.
Adult or child - 50-100/day
Baby - 100/day
Automatic washer 530-50/load
Dishwasher 27-15/load
Garbage Disposer 34-6/day
Kitchen sink (a) 32-4/use
Shower or tub 525-60/use
Toilet flush 34-7/use
Bathroom lavatory sink2 1-2/use
Water softener regeneration550/100/cycle
Backwash filters 10100-200/backwashing
Outside hose faucet 5 depends on run time
Reverse Osmosis water treatment * 3-10 gallons of wastewater per gallon of treated water produced

Notes to Table:
(a) water flow restricting valves and shower heads can reduce flow and water use by up to 50%.
Source: USDA "Water Systems Handbook." (Thanks to Keith Oberg, Professional Home Inspection Service, Binghamton, NY, for providing this information.)
This data is used to estimate daily wastewater use in order to apply the septic tank sizing table located at SEPTIC TANK SIZE

*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 topo 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. See REVERSE OSMOSIS CONCENTRATE WASTE DISPOSAL for further details. -- Larry Newcomb Encinitas Learning Center

We also discuss the effects of increased water usage when buildings use reverse osmosis (RO) for water purification. This article is part of our series: SEPTIC SYSTEM INSPECTION & MAINTENANCE COURSE. Also see The Septic Information Website

Table of Peak Water Demand Usage Rates Translates into GPM Requirements for Water Pumps

Typical Residential Building Water Usage Rates: Flow Rates & Plumbing Fixtures
Water Usage Point Water Flow
GPM1
Peak
Demand2
Water Volume
Gals
Total Water Flow Rate GPM for Number of Bathrooms in Use at Once3
1 1 1/2 2 - 2 1/2 3 - 4 Comments
Bath Sink Lav
4
2
2
4
6
8
 
Dishwasher
2
14
3
3
 
Kitchen Sink
5
3
3
3
3
3
 
Shower
5
35
35
35
53
70
 
Toilet
4
5
5
10
15
20
 
Tub
5
35
35
35
53
70
 
Washing Machine
(Clothes)
5
35
18
18
18
WASHING MACHINES & SEPTIC SYSTEMS
Peak Demand
Total Gallons2
 
45
70
98
122
SEPTIC TANK SIZE
Minimum Water Pump GPM Capacity Needed
 
7
10
14
17
WATER PUMP CAPACITIES TYPES RATES GPM
Gallons Per Hour Flow Rate
 
420
600
840
1020
 

Notes:

1. These are WSC's average fixture flow rates for common household plumbing fixtures. In some cases new fixtures are provided with low-flow-rate orifices or heads that can substantially reduce these flows. For example shower heads may restrict flow to about 2 gpm as may lavatory faucets.

2. Average household total gallons of water used during a theoretical peak demand period of seven minutes. I.e. all fixtures are in use overlapping in time for this interval. This is the peak demand water volume used just during that interval. In my OPINION these numbers may not represent typical household usage.

For example someone washing dishes by hand at a kitchen sink usually runs water for longer than 3/5 of a minute (3 gallons taken at a 5 GPM rate means that the kitchen faucet was open for just about 36 seconds or that water was run more slowly so as to consume 3 gallons over a 7 minute interval).

3. Notice that there is a presumed reduction in flow rate when multiple bathrooms are in use simultaneously. For this reason the individual or single fixture flow rates are not simply added together. The table also assumes that either a shower or tub is in use in a given bathroom but not two such fixtures in the same bath for the same interval.

Adapted from: Water Systems Council (2003)

 

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