VIEWPOINT: Cutting household water use

Claremont has a serious water problem. Its dimensions became glaringly clear on April 18 when the State Water Resources Control Board (SWRCB) announced that the City of Trees must reduce its residential consumption of water by 36 percent. That is the highest tier of reductions statewide, putting Claremont on a par with the much-maligned Beverly Hills and Rancho Santa Fe.

Put another way: our per capita water usage is nearly double the national average, one-and-a-half times higher than the state average and significantly higher than Upland, La Verne or Pomona.

It’s useful to look at some Claremont data for residential use so that you can compare directly with your monthly Golden State Water bill. In 2009, Golden State developed a histogram showing annual water use for 9,317 single-family residences in Claremont residences, revealing that:

• The average consumption of water per day in Claremont residences was 588 gallons in 2009. Note that a gallon of water weighs 8.34 lbs, The average Claremont residence uses nearly 2.5 tons of water daily!

• One ccf (one hundred cubic feet) equals 748 gallons, hence 588 gallons per day is equivalent to 23.9 ccf per month. If your monthly water bill shows that you are using more than this on average throughout the year, see the suggestions below to help you decrease your consumption.

Although six years old, we believe the numbers have not changed substantially since then, which is why the SWRCB is requiring us to slash residential consumption. Here are three of the many steps we can take to reduce water use:

1. Because more than half the water we consume is for outdoor irrigation, it is imperative that we replace lawns with local plants or other surfaces that do not require as much water.

Most of us use roughly 8 ccf per year for each 100 square feet of grass (or 5984 gallons); it takes at least 160 ccf per year to maintain 2,000 square feet of grass (or 119,680 gallons). Removing that amount of lawn should reduce your average water usage substantially; doing so will qualify you for a significant rebate from Metropolitan Water District by way of Golden State Water Company.

2. Homes with an uncovered swimming pool also lose about five feet of water per year due to evaporation and spillage—enough to completely refill the pool. A pool that is 20-by-40 feet will use 32 ccf of water per year (or 23936 gallons). A pool cover, if used regularly, will save most of this.

3. Typical indoor water usage runs between 150 and 300 gallons per day (gpd), so conservation here is just as crucial.

The greatest use inside most homes is for showers. Old showerheads typically use about 75 gallons for a 10-minute shower; new showerheads use just 25 gallons (or less). Replacing old showerheads that are used twice a day should save about 100 gpd. Heating water for showers costs about a half a cent per gallon for a gas water heater or 1.5 cents per gallon for an electric water heater. Saving 100 gpd of hot shower water a day should save about $15 on monthly gas bills or $45 on monthly electric bills. Taking shorter showers will make a major difference.

The second largest use of water inside most homes is for toilets. Old toilets use about six gallons per flush, while new low-flow toilets use 1.6 gallons. Replacing old toilets that are flushed (in total) about 12 times per day will save over 50 gpd.

Washing machines are another major user of water. Energy Star-certified front-load washers use on average 13 gallons per load; top-load washers use 23 gallons. Given that the average American family washes 300 loads a year, switching out old machines for more efficient ones could save 3000 gallons annually.

These conservation actions will play an important part in Claremont’s mandatory reductions. So will steep reductions by the city in its irrigation of parks and median strips. Local schools and colleges must be as aggressive, indoors and out. Use less, save more: that’s the key to reaching the state-mandated cut of 36 percent.


Sam Tanenbaum was dean of faculty and is emeritus professor of engineering at Harvey Mudd College; Char Miller is the W.M. Keck Professor of Environmental Analysis at Pomona College; and Richard Haskell is professor of physics at Harvey Mudd College.


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