ISU Extension Publication #: Pm-1089
Author: Dr. Tom Glanville, Dept. of Agricultural & Biosystems Engineering
Date: revised July 1989
Content Review: March 1996 by Dr. Tom Glanville
NOTE: To obtain a fully formatted version of this document that can be viewed and printed with the Adobe Acrobat viewer click
Dollars Down the Drain: Saving Water, Energy, and Money in the Home
Using household water more efficiently-to cut utility bills, stretch the useful capacity of a weak well, or relieve an
overloaded septic system- can result in surprising savings. This publication describes several simple methods for improving water use efficiency.
Saving Water Saves Money
A home in town or in the country can be modified to save energy and money by using less water.
If a household averages three 5-minute showers per day, nearly $60 per year can be cut off the gas
water-heating bill by using a water-efficient showerhead. With electric water heating, the savings would be nearly $150.*
As shown in the example on page 5, three simple plumbing fixture modifications that cost less than $10 can cut
indoor water use for a four-member household by 70 gallons per day. In a community where combined water and sewer charges average $2.50 per 1,000 gallons, using 70 gallons less water per day saves $64 per year.
*Cost saving estimates for the examples inthis section are based on marginal unit costs of$0.45 per 100 cubic feet
for natural gas, $0.06 perkilowatt hour for electricity and a combined charge of $2 50 per 1,000 gallons for water
and sewer service. Consult with your local utilities to determine if your costs differ significantly Annual savings will vary in different locations.
Although most rural home owners do not pay monthly water and sewer bills, many have private water supplies and
septic systems that do not meet their needs. Weak wells or overloaded wastewater disposal facilities can cause
great inconvenience and require major investments of time and money if replacement or expansion is necessary.
Improved water use efficiency reduces demands on wells and septic systems and can minimize or even eliminate the need for more costly modifications.
Ways To Improve Water Use Efficiency
There are many ways to cut water use in the home, but improving water use efficiency is the easiest.
Improvements in efficiency focus on reducing waste, not on using less water than is needed. Many conventional
(nonwater-saving) plumbing fixtures and appliances are not water efficient. However, they can be improved by using the methods presented in this publication.
The methods presented here were selected on the basis of high potential for long-term savings of water, energy,
and money. They are easily accomplished by most home owners at reasonable cost and, once implemented, have little or no impact on the life-style of water users.
Daily in-home water use usually ranges between 50 and 75 gallons per person (about 250 gallons a day for a family
of four). Table 1 shows the typical distribution of water use in a home. Nearly 70 percent of household water is used in the bathroom. Some major savings in water and energy use can be made there.
A nonwater-saving toilet uses 5 to 7 gallons of water per flush. For a family of four this totals 36,500 to 51,000
gallons per year just to flush the toilet.
Water-conserving, shallow-trap models use about 3 1/2 gallons per flush. Most new toilets now on the market are
the shallow-trap type and cost no more than the water-wasting designs. When planning new or remodeled bathrooms, be sure to specify a shallow-trap model.
Table 1. Typical household water use.
Daily use, Approximate proportion
Type of use gallons per person of total use, percent
Toilet flushing 25 40 Bathing 20 30
Laundry and dishes 13 20
Drinking and cooking 4 5
Other 3 5
Total 65 100
If a new toilet is not needed, try modifying the old one to make it more efficient. Commercially manufactured or
homemade toilet tank inserts can be installed to reduce the volume of each flush by 1/2 to 1 1/2 gallons.
Tank dams, like those in figure 1, can be bought from plumbing supply houses for about $8. They will retain 1 to 1
1/2 gallons per flush. Plastic bottles, like the milk container and the soap bottle shown in figure 2, make effective
homemade tank inserts. Trim to a suitable height if necessary, place in the tank, and allow to fill with water. Add a
few small stones or some sand to prevent movement during toilet flushing. The volume of each flush will be reduced by the amount of water retained inside the bottles (usually 1/2 to 1 gallon).
Figure 1. Tank dams can make a toilet more water efficient.
Bricks are not good inserts because they flake off inside the tank and interfere with proper sealing of the flush
valve. If accidentally dropped while being inserted, a brick can break the tank.
Bending the float arm (identified in figure 3) to lower the water level in the tank is not a good water-saving
method. This reduces the pressure and velocity of the flushing action and may adversely affect performance. The filled tank level should be about 1/2 inch below the overflow tube for good performance.
Figure 2a. Plastic bottles make good toilet tank inserts.
Figure 2b. Trim containers to suitable height and add sand or stones for ballast
Figure 2c. The float ball can be temporarily unthreaded from the float arm for placement of a large container.
Figure 2d. The float ball is reinstalled and inserts are ready for use.
Nonconserving shower heads commonly deliver 5 to 6 gallons per minute (gpm). Some have maximum flow rates as
high as 10 to 12 gpm. Waterconserving models are designed to provide a pleasant, well dispersed spray pattern at normal household pressures using only 2 to 3 gpm.
In many cases, a conventional showerhead can be made more efficient by installing a flow restrictor in the line
ahead of the fixture. Figure 4 shows three types of flow restrictors.
The gasketed brass orifice (lower left, figure 4) was installed ahead of the shower fixture shown in figure 5,
reducing the delivery rate from 6 gpm to less than 3 gpm. Installation took less than 15 minutes and the insert cost less than $2.
While performance of this showerhead was not greatly affected, some models require a high flow rate to provide a
well dispersed spray pattern. Showerheads that do not perform well with a flow restrictor usually can be replaced. with an inexpensive, water-saving model.
Figure 3. Toilet tank flush and fill mechanisms.
With the flow restrictor installed, a 5-minute shower that previously required 30 gallons of hot water now requires
less than 15 gallons. This means that a family of four averaging three 5-minute showers a day would save approximately 16,400 gallons of hot water per year.
Using an energy-efficient gas water heater, it costs about $60 to heat this amount of water to bathing
temperature. Electric heating would cost about $150. Few other improvements in home energy efficiency can be made as easily and yield the substantial savings obtained by conserving hot water.
Figure 4. Three types of shower flow restrictors. Lower left: gasketed brass orifice insert. Center: external
restrictor (installed ahead of showerhead). Lower right: rubber insert.
Figure 5. Installing a shower flow restrictor.
Figure 5a. Restrictor is pressed into threaded collar of showerhead.
Figure 5b. Flow restrictor in place.
Figure 5c. Showerhead in operation at 3 gallons per minute.
A steady drip from a leaking faucet can waste 300 gallons of water a month. A leaking hot water tap also wastes
costly energy. Faucet leaks usually are caused by worn washers-a problem that most do-it-yourselfers can remedy quite cheaply.
One of the largest water leaks in the home may go unnoticed because it is hidden inside the toilet tank where a
misaligned or worn flush valve (figure 6) can let 100 gallons a day (36,500 gallons a year) or more seep undetected, through the trap, and down the drain.
If you listen carefully/ you may hear a trickling sound as water leaks into the toilet trap or as the float-controlled
ballcock replenishes the water supply inside the tank. Because this leakage can occur almost noiselessly, dye testing is a more reliable means of detecting internal leakage.
To dye test your toilet, remove the tank cover and add several drops of food coloring to the water (figure 7). Wait
10 to 15 minutes. If color appears in the trap, the flush valve is leaking. Check the flush valve seat for corrosion or
scale and make sure the flush valve ball is aligned with the valve seat. If this does not help, the valve probably is worn and should be replaced (see figure 8). Valves are available at most hardware stores.
Figure 6. A leaking flush valve permits hidden internal toilet leakage.
Figure 7. Dye testing procedure for internal toilet leakage.
Figure 7a. Place food coloring in toilet tank.
Figure 7b. Wait 15 minutes. Color appearing in toilet trap signals a leak.
While you have the tank cover off, be sure to check the high water level. The float-controlled ballcock should fill
the tank to about 1/2 inch below the top of the overflow tube (internal parts are identified in figure 3).
Tremendous quantities of water can be wasted if the water level reaches the top of the overflow tube. The fill level can be lowered by gently bending the float arm.
The ballcock assembly occasionally becomes worn or fouled with scale, preventing shut-off of the water supply at
the desired level. Replacement units can be purchased for $10 or less.
Estimating Your Savings
A few dollars invested in improved water efficiency can yield substantial annual savings. Tables 3 and 4 can help in
estimating potential savings. The following example shows how.
The Splashers, a family of four, used 270 gallons of water a day before making some water-saving improvements.
After improvements, daily water savings amounted to 70 gallons per day with 50 gallons of this being heated water (table 2).
Using two plastic bottles as toilet tank inserts, the Splashers reduced their
Figure 8. Worn flush valve (note wear ring at pencil point) can cause internal toilet leakage.
toilet flush volume from 5 gallons to 4 gallons per flush.
A flow restrictor installed in their showerhead cut the flow from 6 gallons to 3 gallons per minute.
The Splashers also discovered a leaking hot water faucet in the basement that wasted 5 gallons per day.
Natural gas costs $0.45 per 100 cubic feet in the Splashers' home town and the combined water and sewer charge
is about $2.50 per 1,000 gallons.
From table 3, saving 70 gallons of water per day reduced the Splashers' annual sewer and water costs by $64 per
year (indicated in bold type).
The 50 gallons per day savings of heated water cut the Splashers' annual energy bill for natural gas by $65, as
shown in table 4 (indicated in bold type).
The following publications that may be of interest are available from county extension offices in lowa or from
Publications Distribution Center, Printing and Publications Building, lowa State University, Ames, lowa 50011: Pm-840 Good Wells for Safe Water Pm-899Shock-Chlorinating Small Water Systems
Pm-938 Home Sewage Treatment- Conventional Methods and Equipment Pm-986 On-site Wastewater Treatment
Using Mound-Type Systems
Pm-1328 Plugging Abandoned Wells Pm-1329 Coping with Contaminated Wells
Pm-1335 Sampling Your Drinking Water
Pm-1334i /s Your Drinking Water Safe? Pm-1334j Abandoned Wells: Open Threat to Your Health and Safety
Table 2. Daily household water use for the Splasher family.
Water used before Water used after
Type of use improvements, gallons improvements, gallons
Toilet, 20 flushes per day 100 (5 gal. per flush) 80 (4 gal. per flush)
Shower, three 5-minute 90 (6 gal. per minute) 45 (3 gal. per minute)
showers per day
Laundry and dishes 52 52
Drinking and cooking 16 16
Other 12 (5 gal. due to 7
Total 270 200
Table 3. Estimated annual savings on water and sewer bills (rounded to nearest dollar)
Average daily Combined water and sewer service charge
water in dollars per 1,000 gallons
gallons $2.00 $2.50 $3.00 $3.50
10 $7 $9 $11 $13
20 15 18 22 26
30 22 27 33 38 40 29 37 44 51
50 37 46 55 64
60 44 55 66 77
70 51 64
80 58 73 88 102
90 66 82 99 115
100 73 91 110 128
Table 4. Estimated annual energy savings from improved hot water efficiency in the home. (rounded to nearest dollar)
Gallons of Natural Gas Price Electricity Price
hot water cents per 100 cubic cents per kilowatt-hour
saved daily 45 55 65 4.0 5.0 6.0 7.0 8.0
5 $6 $8 $9 $11 $14 $16 $19 $22
10 13 16 19 22 27 33 38 44
15 19 24 28 33 41 49 57 65
20 26 32 37 44 55 65 76 87
30 39 47 56 65 82 98 115 131
40 52 63 75 87 109 131 153 175
79 94 109 136 164 191 218
60 78 95 112 131 164 196 229 262
70 91 111 131 153 191 229 267 306
The appropriate unit price for natural gas or electricity will depend on the pricing schedule of your energy supplier
and your normal energy use during the billing.
Energy savings increase with the temperature of the water saved. With the exception of automatic dishwashers,
which operate near 140¡F, most warm water uses are between 100 and 110¡F Typical shower temperature is
107¡F The table is based on a water temperature of 107¡F Dollar savings will be greater for savings of water with temperatures greater than 107¡F
Ames, lowa 50011
Pm-1089 | Revised | July 1989
File: Engineering 6
-- and justice for all
The lowa Cooperative Extension Service's programs and policies are consistent with pertinent federal and state
laws and regulations on nondiscrimination regarding race, color, national origin, religion, sex, age, and handicap.
Cooperative Extension Service, lowa State University of Science and Technology and the United States
Department of Agriculture cooperating. Elizabeth A. Elliott, interim director, Ames, lowa. Distributed in furtherance of the Acts of Congress of May 8 and June 30,1914.
Prepared by Tom Glanville, extension agricultural engineer.
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