Testing Electric Water Heaters

[Rick Bunzel]

Typically I will run the shower for 12 minutes and watch for a temperature drop. Normally if I see a greater than 20 degree drop (on a 50 gallon tank) I suspect an issue with the dip tub or bad element. A builder claimed he talked to the manufacturer and that kind of drop in 12 minutes was normal. I think he is blowing smoke up my b##t but want to see how everyone else is testing electric hot water heaters???


//Rick

[Rick Cantrell]

Typically I will run the shower for 12 minutes and watch for a temperature drop. Normally if I see a greater than 20 degree drop (on a 50 gallon tank) I suspect an issue with the dip tub or bad element. A builder claimed he talked to the manufacturer and that kind of drop in 12 minutes was normal. I think he is blowing smoke up my b##t but want to see how everyone else is testing electric hot water heaters??? //Rick

20 deg is a big drop for a shower in only 12 minutes.
But it would not be a burned out element or bad thermostat.
It could be the dip tube or even the upper thermostat is set to a higher temperature than the lower thermostat. Setting the thermostats at different temps is not that uncommon.

I test a WH much the same as you.
TYPICAL
Run until hot at each fixture to check that each fixture is properly plumbed.
Run hot at tub for 6-8 minutes, (40-50 gal tank)
Check Temp at start and end.
>15 deg, I report findings and recommend WH be serviced/repaired, may need to be replaced.

There are a lot of (too many) variables:
Size of WH
Sediment in tank (unknown)
Starting Temp of water
Temp of incoming water
GPM Flow rate of fixture
Is there a Tempering valve and/or hot water recirculating pump

[Mark Reinmiller]

Typically I will run the shower for 12 minutes and watch for a temperature drop. Normally if I see a greater than 20 degree drop (on a 50 gallon tank) I suspect an issue with the dip tub or bad element. A builder claimed he talked to the manufacturer and that kind of drop in 12 minutes was normal. I think he is blowing smoke up my b##t but want to see how everyone else is testing electric hot water heaters???


//Rick

I would question the accuracy of that test. Not all showers have the same flow rate and not all water heaters are set to the same temperature.

Having never performed this test myself I don't know how consistent your results are, but if you end up flagging a fair percentage of water heaters I would be suspect of the test.

[Bruce Ramsey]

With a 1.5 gpm low flow shower head for 12 minutes that is 18 gallons. 1/3 of a 50 gal water heater. If water heater is set at recommended standard of 120 degrees, and you introduce 18 gallons of 65 degree water, that is a lot for the elements to keep up with.

[Rich Goeken]

With a 1.5 gpm low flow shower head for 12 minutes that is 18 gallons. 1/3 of a 50 gal water heater. If water heater is set at recommended standard of 120 degrees, and you introduce 18 gallons of 65 degree water, that is a lot for the elements to keep up with.
But it appears to be a good rule-of-thumb test. It would be interesting to see what the actual exiting temperature is on a new installation at the 15 minute mark, or 10 minute mark if you prefer, summer and winter (for you folks in the Great North areas too ;) ). However, the temperature may also vary with the fuel source and age of the unit, and then experience takes over at this point.