Is this water heater working correctly?
November 29, 2017 8:25 AM   Subscribe

We recently moved into a rental house and I need help diagnosing what is going on with the water heater.

It's an electric water heater - 50-gallon capacity. It has not been delivering enough hot water to complete two consecutive showers, with the first shower being me and less than 5 minutes. I ran a test yesterday in the late afternoon when I knew no hot water had been used for hours, and thus the water heater should be full.

The flow rate at the kitchen faucet is 1.25 G.P.M.

The water temp at the start, with the hot tap at 100% was 124F. I had both thermostats set at 130F. So that seems fine.

At 19 minutes (so about 23 gallons consumed) water temp. had dropped to 102F.
At 25 minutes (about 31 gallons consumed) water temp down to 90F.

Googling the symptions tells me that a bad lower thermometer is a likely explanation for these symptoms. The homeowner's opinion is that we should just take quicker showers.

After the experiment, I increased the lower thermometer to the max - 150F. Which of course you really shouldn't do as its bad for your electricity usage. This morning water was scalding hot (140F+) initially, and good hot water was maintained through my wife's shower.

So is it problem solved, or am I working around a bigger issue with the water heater? My experience is all with gas hot water, so I have no experience with electric. Having to run it at max temperature tells me that the hot water heater at a minimum is not operating efficiently. I just want to document all this with the property management company so that if it fails completely while I'm here they can't pin the blame on me somehow.
posted by COD to Home & Garden (6 answers total)
Try setting the temp higher. You will use less hot water for your shower, leaving more for the next person.
posted by theora55 at 8:49 AM on November 29, 2017 [1 favorite]

Here's a good graphic explanation of how the heater is supposed to work with upper and lower elements coming on sequentially. In your case the lower element is burned out, or the lower thermostat is broken as you suggested. You might run a longer test and submit the info to your landlord (also time your showers and provide that info, assuming your showers are average length which Google sez is 8 minutes), mentioning that if he is not going to fix it, you are going to have to run the heater at 140 or 150 and risk scalding yourselves in order to be able to shower. Maybe put it in writing to emphasize the risk which could be a liability to him.
posted by beagle at 9:08 AM on November 29, 2017 [1 favorite]

So is it problem solved, or am I working around a bigger issue with the water heater?

It could be sediment/lime build up has diminished the capacity of the tank.

Alternatively, one of your electrodes could be worn out. There is a sacrificial anode that slows down the decay of the electrode, and that is not a perfect solution. Anyway, they are to some extent, pretty easy to replace.

I run my hot water heater at about 140 degrees so we use less hot water for showers and such. Our faucets all have temperature regulators to prevent scalding though. In any event, that works around, but does not solve, the other problem whatever it is.
posted by Pogo_Fuzzybutt at 9:10 AM on November 29, 2017 [1 favorite]

do you have a multimeter? even a cheap, shitty harborfreight one?
posted by Dr. Twist at 9:38 AM on November 29, 2017

do you have a multimeter? even a cheap, shitty harborfreight one?

Yes - yes I do. And I even know how to use it. What do I need to check?
posted by COD at 11:22 AM on November 29, 2017

Disconnect the power from the water heater at the breaker box and disconnect the wires from the heating elements. Put the multimeter on the resistance (ohms) setting and measure the resistance between the screws on the heating elements. you should get somewhere in the neighborhood of the square of volts listed on the element divided by watts listed on the element. it wont be exact but it wont be very small or very big. probably between 10 and 40 ohms for a 240V element. If its not, you have a bad element. after that , check if there is any measurable resistance between tither of the screws and the hex nut part that you use to screw the element in. if you get anything above zero, you have a bad element

to check the thermostats, reconnect the wires to the elements. and set the temperature to maximum. check the resistance between the lower two screws on the top thermostat, if it's near zero. the thermostat is good. to check the lower element, turn the upper element to the lowest temp setting (sometimes you can hear it click). stet the lower element to maximum and check the lower screws with the wires going to the element. it should read zero too if the thermostat is good.
posted by Dr. Twist at 9:11 AM on November 30, 2017 [1 favorite]

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