Water Heater Recharge Troubleshooting

[Jimmy H NYC]

I have an AO Smith 50-gal XCVT 50 (series 100) gas-fired water heater. Built 11/2007, so I don't think it is one of the recall models. Seems lately not to be recharging like it used to. Is there a way to actually test the recharge performance using a clock, a thermometer and a bathtub, or whatever. And then to troubleshoot the problem if there is one, before I start calling the plumber?

Also, is it still under warranty?

Finally, if it is the dip tube, is that worth replacing, or just replace the whole thing?

Thanks for all your help. You guys run a wonderful website here and I really appreciate all you do.


-Jim

 

[Terry]

A water heater that old may have some sludge at the bottom of the tank, or the dip tube may be breaking off. If the dip tube is an issue, you normally see it clogging the aerators on faucets.
A heater that is nine years old is getting up there. Most plumbers don't like spending much on something that could fail shortly after working on it. It makes the plumber look bad for charging for the repairs, and then the water heater decides to just quit. I've seen some gas water heaters fail at seven years before.

 

[Sponsor]

 

[Jimmy H NYC]

Thanks for the quick reply! My additional concern however is, am I hallucinating or is there really a problem? Is there a way to measure the recharge rate? Maybe it is working fine, and I am just getting old and hypersensitive?
-Jim

 

[Reach4]

I am thinking that you are saying that 40 gallons or more come out plenty hot, but the next 40 takes more time to warm up.

Do you have well water or city water?

You might consider flushing the WH. Flushing is more than just draining IMO. This is my idea of a minimum:

To flush sediment from the water heater, you can drain the water.
Then turn on the supply pipe on full with the drain open. Turn off
the water until most of the draining stops. Repeat one or more times.
The surge can help wash stuff out.
​

I am not a pro.

 

[Jimmy H NYC]

city water. also, actually even the first 40 seems shallow. the first 20 seems okay... then it gets tepid... but again,I would have to measure. that is the data and protocol i need. how to measure? what should the temperature be after 10, 20, 30, 40 gallons? How long should it take, if it is working properly, to recover to x degrees?

 

[Dj2]

Your WH may be showing signs of the beginning of the end. Start putting money away for a new WH.

The last thing you want is a WH that fails when you need it the most. At 9 yo, it can happen soon.

BTW, not to contradict myself - I've seen gas fired WHs last more than 12 years before.

 

[Jadnashua]

As a WH ages, depending on your water chemistry, it can nearly fill up with mineral deposits severely limiting both the heat transfer and the volume of water it contains. There's typically a dip tube that directs the cold, incoming water towards the bottom of the tank, and those can disintegrate, which means that instead of inserting the cold water near the bottom of the tank, it mixes with the hot that tends to migrate towards the top, limiting the amount of really hot water you can get out of it. Because of that mixing, either the normal amount or the degraded one, you can never get all of the hot water out of the tank based on the volume listed. If the air inlet port gets clogged up, your burner make not get as hot as originally designed, and it will produce more CO, but that might just go up the flue, verses being a health issue to the occupants. Doesn't help the environment as you'd also be using more fuel than needed and the incomplete burning adds its own pollutants.

The first hour draw takes into account the amount of hot water in the tank, and the burner trying to keep up (it's rare that it can if you continue to draw a high volume), but that added heat from the burner does help increase what you can get out of it. The first hour draw will vary based on the rate at which you draw off the water.

 

[Master Plumber Mark]

You probably have a broken off dip tube down in the heater and its only
really able to heat half as much as it used to do..... you can only take one shower
then it turns cold... that is a sign that the tub and broken off and the cold water is not being forced to the
bottom of the heater...