Strange (to me) water heater issue

So, this one has me stumped - likey because I don't quite understand the anatomy of a water heater.

A Rheem Power Vent 50 gallon unit. Pretty certain it's old - the serial number starts with 03/93.

I get an initial burst of water pressure when first opening the hot water side of a fawcet but then quickly slows to just a little more than a trickle. Water starts warm but then goes cold. Hot from the T&P valve, drain valve as well.

Cold water pressure is normal. What seems strange is that the cold supply line (copper) into the top of the unit definately feels a little warmer than does the hot supply line, but neither are hot. Burner lights normally.

Aside from the main shut off gate valve there are no other valves inline. Guess there's a restriction somewhere but can't understand where. Any ideas?

Thanks,

Dan

ss3964spd said:

Cold water pressure is normal.

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Flow rate is what you need to measure. A 1 gal container filled in 10 seconds is 6 GPM.

Thanks for that, but when I turn a fawcet to cold flow is normal. Turn it to hot, flow starts strong and warm but tapers off to very low within 15 seconds and goes cold.

Discharge from the T&P, as well as the tank drain, is hot.

Dan

Not enough information to make a diagnosis, but the problem could be in the faucet if that is the only place it happens.

Thanks for the reply hj.

No, does not matter which faucet - same symptom at all of them. Cold water flow and pressure is normal at each fixture, hot is not.

Seems to me that it has to be something to do with the water heater just can't figure out what.

The flow could be caused by plugged check valves in the nipples on the inlet and outlet of the tank. The change in temp though sounds like a cracked dip tube that carries the cold water down to the bottom of the tank.

Makes perfect sense Jerome. Time to get the pipe cutter out.

Thanks,

Dan

Turns out the dip tub was both almost fully blocked with gunk at it's opening and cracked along it's length.

Problm solved.

Many thanks,

Dan

There might be a recall on it.

My AOSmith diptube disintegrated and left me with shell-like chunks in the aerators-I couldn't imagine where they came from or what they were but my plumber knew immediately.

Looks, it's a 17 year old water heater. Yes, there was a period of time that there were lots of bad dip tubes in all makes of heaters, my old Richmond (Rheem) was one. That said, do you really think you can get any warranty on a 17 yo heater? It's very fortunate that it is still alive. Buy a new dip tube, put it in, and maybe get a little more life out of the thing, but forget the warranty!

Thatguy said:

There might be a recall on it.

My AOSmith diptube disintegrated and left me with shell-like chunks in the aerators-I couldn't imagine where they came from or what they were but my plumber knew immediately.

Click to expand...

Actually there was a class action on it where they would give you a new diptube. That class action settlement period is long over...

Any water heater covered by that settlement is at least 13 years old and replacement should be considered....