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3.4: Indoor Water Use

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    Learning Objectives

    In this section, you will:

    • Analyze indoor water consumption
    • Audit and track your own indoor water use

    When you start to talk to people about conservation, they generally want to discuss ways of reducing their indoor water consumption, particularly bathing less. This is a problem - most of the water in the residential sector in California is used outside! And, frankly, no one in conservation wants to decrease basic hygiene of the general public. Still, indoor water use and conservation is not a bad place to start because it is a place people are very familiar with.

    In the graph below, based on real data from residential homes, you can see that toilets are the biggest users of water in the home, followed by showers and faucets, and then clothes washers. Surprisingly, 14% of all water metered to the home is also lost to leaks. That puts an interesting spin letting a leaky faucet drip. It’s using only a little less water than your faucets!
    Figure \(\PageIndex{1}\): Residential Indoor Demand by the EPA is in the public domain

    Let’s return to our inventory of your bathroom fixtures. What did you discover when you inventoried your bathroom?


    _____ gallons per flush


    _____ gallons per minute at 80 psi

    Bathroom faucets

    _____ gallons at 60 psi


    How many gallons does your toilet use?

    Sometimes it is difficult to tell how many gallons per flush a toilet has by observation. But if you remove the tank lid, often the number of gallons per flush is stamped somewhere on the inside of the tank at the top. In some toilets, you can also find the gallons per flush on the flat surface behind the seat lid. And, of course, in a store, the gallons per flush is written on the box. If you are browsing in a store, a toilet with the WaterSense label guarantees that the product is 1.28 gallons per flush.

    WaterSense Label by the EPA is in the public domain
    Figure \(\PageIndex{2}\)

    In the United States (as of 2017), you can purchase 1.6 gallon per flush toilets in most states, which is the federal standard, but in California, you can only purchase 1.28 gallon per flush toilets. This is 20% less water used per flush. (1.28 compared to 1.6). Yuck! you may say. That’s not enough water. Actually, it’s plenty. Some of us remember the early 1990s, which was the time “low-flush” (a.k.a. low-flow) toilets came on the market in California. These were the first toilets that used 1.6 gallons per flush. Unfortunately, most of them were not re-engineered from the 3.5 gallon per flush toilets of the previous generation. A 1.6 gallon per flush toilet was pretty much a 3.5 gallon per flush toilet with less water. And these did not work well. Water agencies up and down the state of California had to deal with angry customers who felt that the water agency rebate had “recommended” a toilet with poor performance. No one wants a repeat of this. The current 1.28 gallon and 1.6 gallon per flush toilets work well. To check the performance rating of your toilet, see for an entire database of toilet rankings.

    Toilet-Related Conservation

    Toilet rebates are a “classic” conservation program and a favorite of many in conservation. Why? The toilet stays in place for a long time. The savings are essentially “hard-wired” into the home. In this type of rebate program, a customer buys an approved product from a list, and the water agency gives a check or a credit on the bill after the purchase of the toilet. In order to receive the credit or check, the customer must present the receipt and purchase from the list. The approved list is important. It is a best practice to only rebate fixtures that are more efficient than what is standard in the market. Otherwise, you are essentially rebating for people to replace something with a fixture they would have purchased anyway. So if a high-efficiency toilet (1.28 gallons per flush) is on the market, customers shouldn’t be rebated for purchasing it because you are not incentivizing an increase in efficiency. They should be rebated for purchasing an ultra-high-efficiency toilet (1.0 gallon per flush or less).

    Sometimes retail water suppliers will run a one-day toilet giveaway program. In this conservation program, people come to a central location, such as a big park, and pick up a new toilet after providing a driver’s license for identification purposes and a water bill (with a matching name). They are allowed to take the toilet home, but they must return two weeks later to drop off the old toilet to the park (in a giant dumpster) or they will be charged for the new toilet on their bill. This guarantees (almost!) that the new toilet is installed at the home in the service area. This is one model for success but involves a lot of coordination and disposal of old toilets.

    Misconception Alert!

    You have probably heard, “If it’s yellow, let it mellow. If it’s brown, flush it down.” Do not do this. Please keep flushing your toilets. This is advice from the 1980s when toilets used 3.5 gallons per flush or more. It wasn’t bad advice then (though still sort of gross), but it’s terrible advice now. Upgrade your old toilet with a 1.28 gallon per flush toilet and keep flushing. We don’t want to keep waste in our homes, and if you have kids, it’s a hard-to-break habit if they learn not to flush. Keep flushing!


    It may be hard to tell how many gallons per minute a showerhead uses just by looking at it. Many showerheads are labeled with this information, but calcium and magnesium in hard water build up to obscure the numbers. In the United States, you can buy showerheads with up to a 2.5 gallons per minute rating, but in California, the only showerhead you can buy is 2.0 gallons per minute or less. To earn a WaterSense label, a showerhead would also need to use 2.0 gallons per minute or less.

    Shower-Related Conservation

    Many water agencies have giveaway programs with showerheads. One of the challenges with a giveaway program is that the water agency typically does not know that the product is installed properly (or installed at all). So the water agency may “count” on the savings from purchasing and distributing showerheads, but not necessarily receive the savings as a decrease in overall consumption.
    Figure \(\PageIndex{3}\): Shower Better image by the EPA is in the public domain

    Additionally, and equally problematic to conservation program design, showers are seen as “sacred” by many people. It’s their “me” time and they do not want you to mess with their shower, including affecting the quality with a sub-par showerhead and length of shower.

    Washing Machines

    A traditional style washing machine uses 40-50 gallons per load of laundry. That’s a lot! A high-efficiency washing machine uses about half of that (20-25 gallons). That’s a significant savings. But, of course, high-efficiency washing machines cost more - typically $200 more than a traditional machine (as of 2016). A high-efficiency machine typically soaks the clothes longer to remove stains and dirt rather than using a central agitator. The loads of wash may take longer in a high-efficiency machine.

    Washing-Machine-related Conservation

    Many water agencies operate washing machine rebates, which offer a rebate of $100-300 to make the purchase more cost-effective for consumers. Washing machines rebates have mostly replaced toilet rebates in popularity in California. While it’s possible that a customer may receive the rebate and move out of the water agency’s service area, it’s also equally possible that a customer may move in with a high-efficiency machine already.

    Image of bathroom faucet by the EPA is in the public domain
    Figure \(\PageIndex{4}\)

    A standard faucet purchased in the United States uses 2.2 gallons per minute. A WaterSense approved faucet will use 1.5 gallons per minute. Aerators can be added to standard faucets to inject air into the water flow and make the flow seem fuller with less water.

    Faucet-related Conservation

    Aerators are typically available at water agencies for free and are given away at events. As with showerheads, aerators are difficult to track and impossible to make sure they are installed properly. They can also present problems in giveaway programs in that customers may need a male or female threaded aerator, but take one of each to hedge their bets.


    Do you remember the table where you quantified your measurements of indoor fixtures? An “audit” is really an extension of that exercise. You make a list of all the water-using fixtures in the house, quantify their use, decide on a number of times per day, and come up with a total. Completing the table below will help you audit your own home.

    Try It!

    Complete the table below to audit your own home (indoor water use).


    Amount of Water Used per Use

    Times Used per Day

    Total Water Used per Day by Device

    Toilet #1

    _____ gallons per flush

    Toilet #2

    _____ gallons per flush

    Toilet #3

    _____ gallons per flush

    Showerhead #1

    _____ gallons per minute

    Showerhead #2

    _____ gallons per minute

    Showerhead #3

    _____ gallons per minute

    Bathroom faucet #1

    _____ gallons per minute

    Bathroom faucet #2

    _____ gallons per minute

    Bathroom faucet #3

    _____ gallons per minute


    Kitchen faucet

    _____ gallons per minute


    _____ gallons per use

    Other Water Using Devices

    Total Water Used Per Day


    In what category is the most water used per day?

    What could you do to save the most water in your home?

    This page titled 3.4: Indoor Water Use is shared under a CC BY license and was authored, remixed, and/or curated by Stephanie Anagnoson (ZTC Textbooks) .

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