Rheem Technical Bulletin
How to Conduct a Proper Draw Test
This document outlines the procedure for conducting a proper draw test on a water heater.
Ensure water heater is satisfied.
a. The water heater should have been recently satisfied. If not, then turn on some hot water until the burner or element comes on. Allow the water heater to come up to thermostat setting and turn off. Electric heaters require monitoring elements with a meter. Gas heaters can be checked visually.
If a recirculation system is present, isolate the recirculation loop by turning off the pump and setting the pump valve to off.
Note the temperature setting on the thermostat.
Go to the closest tub faucet.
Place a 5-gallon bucket under the tub spout.
Turn on straight hot water.
a. It is crucial to catch the initial cold water from the faucet in this step. This accounts for the unknown quantity of hot water needed to fill the pipe leading to the tub faucet. If hot water is drawn before starting the test, the displaced volume from the tank cannot be accurately determined.
Fill the bucket to the 5-gallon mark.
Test the temperature and record it.
Repeat steps 6 & 7 until at least one to two 5-gallon buckets have been filled beyond 70% of the water heater's capacity. For example, a 50-gallon heater requires drawing 40 to 45 gallons of water.
Examine your findings.
a. The first and the 70% filled buckets will typically show slightly lower temperatures than those in the middle of the draw. This is because the first bucket contains cold water from the pipes, and the 70% bucket contains cooler water from the top of the tank. The temperature in the 70% bucket should be within 10°F of the thermostat setting.
Example Draw Test Results
See the following charts for examples of draw test results. The set point for the water heater in these examples is 120°F.
Typical Draw Test Results
This chart illustrates a typical draw test. The X-axis represents Gallons drawn, and the Y-axis represents Temperature (°F). The temperature starts at 108°F at 5 gallons, rises to a peak of 121°F between 15 and 25 gallons, and then gradually decreases to 80°F at 50 gallons. Key points include: 5 gal/108°F, 10 gal/119°F, 15 gal/121°F, 20 gal/121°F, 25 gal/120°F, 30 gal/119°F, 35 gal/115°F, 40 gal/106°F, 45 gal/95°F, 50 gal/80°F.
Draw Test Results (Bad or Broken Dip Tube)
This chart shows results indicative of a bad or broken dip tube. The X-axis represents Gallons drawn, and the Y-axis represents Temperature (°F). The temperature starts at 108°F at 5 gallons, rises to 120°F at 15 gallons, but then drops sharply, reaching 60°F at 50 gallons. Key points include: 5 gal/108°F, 10 gal/118°F, 15 gal/120°F, 20 gal/112°F, 25 gal/105°F, 30 gal/96°F, 35 gal/88°F, 40 gal/80°F, 45 gal/70°F, 50 gal/60°F.
