Conduct a Water Audit in 30 Minutes or Less

by ‐ Tags: water efficiency, property management

If you’re already tracking your building’s water use and want a deeper understanding of where that water is going on a unit by unit basis, here are 4 tests you can perform to gain that knowledge.  You'll need some basic tools and less than 30 minutes per apartment to perform an effective water audit.  Once you have a little practice, you'll probably only need 15 minutes to quantify how many gallons are going where. 


Only a basic set of tools is  needed.  Things you’ll want:



Note: As you inspect an apartment, be sure to visually check for leaks during each test.



Check toilets for leaks.  In some cases you won’t even need to use a dye tablet because you’ll see water running into the bowl.  If you cannot visually determine if there’s a leak, it’s time to break out a dye tablet.


  1. Remove the lid from the tank.
  2. Place a dye tablet in the tank.
  3. Wait 10 minutes (this is a good time to do some of the other checks)
  4. See if there is any color in the bowl
  5. Flush the toilet until the water in the bowl runs clear again.  Some people use only 1/2 a dye tablet for step 2 in order to speed this step up.


If there was no color in the bowl after 10 minutes, congrats! Your toilet is not leaking from the tank into the bowl.  If there was dye in the bowl, then your flapper is in need of replacement. Remember to visually inspect the supply line connections for leaks.  


Check the flow rate of lavatory faucets.  Even if you can see the stamped flow rate, it’s good to do this test in case the faucet has been tampered with. First take note of if the faucet is dripping or any of the connections to it are. Next, you’ll need your bucket with measurements and a stopwatch or watch with a second hand.  


  1. Place the bucket under the faucet.  
  2. At the same time you start timing, turn the cold water on full blast.  
  3. Let it run for 10 seconds and then turn it off.  
  4. See how much water was collected (in gallons) and then multiply by 6.  This is your flow rate.  So if in 10 seconds you collected .25 gallons of water, the flow rate of the faucet is 1.5 gpm (gallons per minute).
  5. Repeat for all lavatory faucets or a sampling of faucets.


Decide what flow rate is the target for your building.  WaterSense labeled faucets use no more than 1.5 gpm and it’s possible to find aerators that use as little as .5 gpm.  If you decide you want a lower flow rate on your faucets, aerators are a quick and inexpensive fix.  Look for the WaterSense label when sourcing them.  WaterSense ensures both that the flow rate is low and that there is acceptable performance. Nobody likes wimpy water pressure!  


Check the flow rate of showerheads.  This follows the same basic steps as checking the faucets.  You’ll again need a stopwatch and bucket with measurements.  For this test, it’s especially helpful to have 3 hands or a bucket with a handle you can hang over the showerhead.  


  1. Hold the bucket under the shower or hang it up on the shower head.  
  2. At the same time you start timing, turn the water on full blast.
  3. Let it run for 10 seconds, then turn it off.
  4. See how many gallons of water were collected.  Multiply this amount by 6 to determine the flow rate.  
  5. Repeat for all showerheads or a sampling of showerheads.


Decide what the target flow rate for showerheads in your building is.  2.0 gpm is the max flow rate allowed by WaterSense to meet their specifications.  You can also find ones around 1.0 and 1.25 gpm.  

Hot Water Delivery (optional)

Check how much water is used before hot water arrives at the tap.  Everyone hates waiting for the water to heat up before their shower.  Some people have developed entire routines they perform while waiting.  Unfortunately, this also means they likely wander away and let the water run longer than needed, wasting many gallons each day.  For this test you'll need a digital thermometer, stop watch, and bucket with measurements. 


  1. To conduct this test, hot water must not have been run to the apartment within 30 minutes of performing the test.  
  2. Find the fixture that is furthest from the hot water heater.
  3. Place your bucket under the fixture and turn on your digital thermometer.
  4. Turn on the hot water completely, hold your thermometer under the stream, and note the initial temperature.
  5. Once there is a 10 degree rise in temperature, turn off the water.  
  6. See how much water is in your bucket. This is the amount of water in the line between the water heater and fixture.  


In new construction, WaterSense specifications only permit .6 gallons of water to be in the line between the water heater and the furthest fixture.  There is no easy fix for bringing your number closer to this target--rerouting plumbing or using smaller diameter pipe is the only solution.  If you have capital improvements planned that will involve moving or replacing pipes, don’t pass up the opportunity to make improvements!  

This chart will help you determine how much water is in a given run of pipe.  For instance, if you have a 50’ run of ½” Type L copper piping, there would be .61 gallons of water in that length of pipe.  

Water content of different pipe types and sizes

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