How to Figure Out the Gallons-Per-Minute Rating

Underwater view of mother and two sons diving in swimming pool
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Water is a valuable resource in any home. Most communities' water districts charge homeowners for the amount of water that they use. So, it pays to keep a close eye on water consumption in the home by thirsty appliances like the washing machine or in the bathroom with the shower or bathtub.

Every fixture and appliance in your home that dispenses water can be rated based on the number of gallons per minute (GPM) that pass through it. These rates vary widely, depending on the age of the fixture and how water-efficiently it has been designed. Knowing and controlling these GPM rates is the first step in shrinking your water bill costs.

The problem is that few homeowners have any sense of how much water all of their various services are using. But there are simple methods of finding out how much water is used, plus simple ways to limit consumption.

Typical Rates For Common Appliances and Services

First examine some average ranges of GPM for typical household fixtures and appliances. Wherever possible, GPM is the most accurate measuring stick for water consumption.

Gallons Per Minute Consumption (GPM)
Showerhead 2.5-7 GPM
Faucet 2-3 GPM
Lawn Systems 3-10 GPM

In other cases, GPM is not the appropriate figure for the type of service, and the rating changes have been noted. For instance, washing machines run for prescribed periods of time. But those periods have intermittent on-off cycles. Thus, it is more practical to phrase washing machine GPM in terms of gallons per load. In the case of washing machines, the average water consumption rate ranges from 18 to 50 gallons per load. 

Gallons Consumed (Alternative Units)
Bathtub 18-36 gallons per use
Washing Machine 18-50 gallons per load
Dishwasher 15 gallons per load
Toilet See gallons per flush (GPF)

Determine GPM Manually

Meters connected to the water line are the best method of determining GPM. But you can test out your faucet's GPM output easily in either of two ways. Both methods are simple, free, fast, and relatively accurate.

Find GPM by Measuring One-Gallon vs. Time

The one-gallon method is an easier and more reliable method of determining GPM. You only need a watch and a one-gallon bucket.

  1. Place a one-gallon sized container beneath the faucet.
  2. Turn the faucet on at full capacity, then start the timer.
  3. When the water crests the top of a container, stop the timer. Turn off the water.
  4. Take the time from the watch and round figure up or down to nearest "5." So, if the timer reads 17 seconds, you would round up to 20 seconds.
  5. Divide 60 by that number. In the previous example, 60 divided by 20 is 3.
  6. The resultant number is the gallons-per-minute or GPM used. The faucet in this example uses 3 GPM.

Find GPM With the 15-Second Method

  1. Place a large container such as a 5-gallon bucket beneath the faucet. Five-gallon buckets are available at all home centers and hardware stores.
  2. Start a stopwatch and run the water at full capacity for exactly 15 seconds. 
  3. With a gallon-sized container, measure the amount. Use an online unit conversion tool if necessary to convert to gallons, and then multiply this figure by 4. Ideally, the resulting figure should be closer to 2.2 GPM than 3 GPM.

How To Limit Your Water Usage

Considering that the average person uses anywhere from 50-100 gallons of water per day, there are plenty of opportunities to reduce water consumption in your home.

  • Install aerators on faucets. Aerators introduce air into the water stream, making the water feel softer to the touch and limiting its volume.
  • Remove your old, inefficient toilet and replace it with a modern 1.6 GPF toilet.
  • Consider removing luxury items such as swimming pools, fountains, garden ponds, and hot tubs.
  • Purchase and install a low-flow showerhead. In fact, many communities now require that you install low-flow showerheads.
  • Replace old appliances like clothes washers and dishwashers with new EnergyStar-rated appliances. You may even wish to consider washing dishes by hand rather than using the dishwasher.
  • Under the bathroom sink, turn down the two water supply lines to reduce water flow. This is an especially value tactic to use with children's bathrooms.
  • Consider changing out your water-gobbling lawn and replacing it with a xeriscaped garden. Xeriscaping takes advantage of plants that require less water, such as cacti and other succulents.
  • Repair water leaks immediately. Even low volume drips will, over time, waste vast quantities of water.
  • Be conservative: take shorter showers, shut the water off while brushing your teeth, fill the sink with water while washing dishes instead of running the faucet, etc.