Determining and Reducing Gallons Per Minute

Underwater view of mother and two sons diving in swimming pool
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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 controlling your water bill costs.

The problem is that few homeowners have any sense of how much water all of their various services are using.

Typical Rates For Common Appliances and Services

Let's take a look at some average ranges of GPM for typical household fixtures and appliances. In some 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 this case, 18-50 gallons per load. 

Showerhead 2.5-7 GPM
Faucet 2-3 GPM
Lawn Systems 3-10 GPM

And a few other statistics:

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 Without Fancy Meters or Devices

You can test out your faucet's GPM output easily in either of two ways.

The one-gallon method: This is the easier and more reliable method of determining GPM.

  1. Place a one-gallon sized container beneath the faucet.
  2. Turn faucet at full capacity — start timer.
  3. When water crests the top of a container, stop timing.
  4. 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 GPM used. The faucet in our example uses 3 GPM.

The 15-second method:

  1. Place a large container such as a 5-gallon bucket (similar to those "Homer" Buckets found at Home Depot) beneath the faucet. 
  2. Start a stopwatch and run the water at full capacity for exactly 15 seconds. 
  3. With a gallon-sized container, measure the amount and 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 that figure:

  • Install aerators on faucets.
  • Remove old, inefficient toilet and replace with modern 1.6 GPF toilet, such as the readily available and inexpensive Kohler Highline.
  • Consider removing luxury items such as swimming pools, fountains, garden ponds, and hot tubs.
  • Purchase a low-flow showerhead.
  • Replace old appliances like clothes washers and dishwashers with new ENERGY STAR rated appliances.
  • Repair leaks right now.
  • 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.