Gas Water Heater, intermittently cold

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northman

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Hi All. I have a BW water heater that sometimes will be cold in the morning when I want to shower, and it has been much worse lately. Tank is about 7 years old, model #M-1-XR65T6BN. This is a 65 gallon tank with 65,000 BTU, when it is working well it should provide almost continuous hot water.

The tank has auxiliary side ports for space heating, which I use for hydronic floor heating with a Taco pump/exchanger unit. I was initially thinking maybe the floor heating was sucking up all the hot water, but the temps (here in Seattle area) are mild. It has done this very rarely in the past, much more often recently. Does this sound like a funky T-stat, and if so is that a reasonable thing to repair/replace? At 7 years I would hope the tank has a lot of life left, is it worth fixing up?

I did recently hook a hose up to the drain and purge out some of the sediment in the tank, don't know if that somehow contributed to the issue. I am considering draining it all the way down then intermittently turning the water inlet on and off to shake out as much crap as I can, not sure if that will accomplish anything. Thanks for the help.
 

Reach4

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I would do the flush. You could temporarily replace the drain valve with a nipple to get more free flow during the flush. I permanantly replaced my valve with a nipple and a ball valve, but the temporary nipple would have probably been a better idea considering how often I will flush.
 

northman

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Is there a flame when the water is cold?

Hard to say, as I don't know it's cold till after I try it, by which time the burner will be on trying to catch up. I don't know that it has anything to do with it, but I also have a hot water recirc pump for the long pipe run to the kitchen, that return T's into the space heating return. So I can have a low volume of warm water dumping into the return, perhaps that is fooling the T-stat? The recirc works on a timer, perhaps I can play with that and see if anything changes.
 

Jadnashua

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If I understand you, your recirc system mixes potable water with the hydronic heating water? Generally, a big n0-no! They should be entirely separate. There typically should be a checkvalve in the recirc line somewhere, and it may be sticking open. WHen that happens, you're drawing water through the path of least resistance, and that may be from the recirc line which is all cooler water.
 

northman

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If I understand you, your recirc system mixes potable water with the hydronic heating water? Generally, a big n0-no! They should be entirely separate. There typically should be a checkvalve in the recirc line somewhere, and it may be sticking open. WHen that happens, you're drawing water through the path of least resistance, and that may be from the recirc line which is all cooler water.

Not exactly. I have a heat exchanger in the Taco unit, so the potable side is isolated from the floor heating. The recirc Ts back into the potable side return, and it does have a check valve.
 

northman

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Is there a flame when the water is cold?

Update: This morning I checked the tank first thing, it was not firing when I got up. I recently reset all the hydronic t-stats so that they would put no demand on the system in the early morning hours. Shower was lukewarm with the shower valve on the full hot position. I verified that the water was similarly lukewarm at a different faucet.

So it appears to me the water heater t-stat is funky. Does anyone know if that is an easy fix on a Bradford White tank? I don't mind paying a plumber if that is the right way to do it, but if I could fix it myself that would be cool. Anyone know what this might entail?
 

Jadnashua

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At 7-years old, that tank could be on its last legs (or it could last another 7-years, but that would not be common!). It's not the best thing to mess with gas appliances unless you know what you are doing, so paying a plumber to replace the gas valve may go a fair ways towards a new tank. A new one would likely also be more efficient.
 
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