Leaking T&P Valve on water heater

secutanudu

Gas water heater, very slow drip out of T&P valve. I replaced the valve 2 days ago, and no water came out since then. This morning, there;s a small amount of water in the bucket below the valve.

There is an expansion tank hooked up to both the water heater and boiler (same tank for both). Any ideas? Could the expansion tank be shot? Should the water heater have its own?

Thanks.

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Andrew

LateralConcepts

What is your water pressure?

majakdragon

The expansion tank could be flooded or plugged. You also need to check the pressure on the system. Not sure if you have a way to check the temperature too. There are usually only 3 reasons the T&P valve leaks. High temp, high pressure and broken.

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LateralConcepts

Also how old is the water heater? Has it ever been serviced/drained? Does it make any noises, i.e. popping crackling type sounds when heating?

Being just a couple days ago, could the small drip be residual water that was leftover from the old one leaking?

AllanJ

How can the same expansion tank be connected to both the water heater and the boiler? Boiler water must not be commingled with domestic hot water.

A rough and serviceable recalibration can be done to the expansion tank (with or without bladder) above the pipe by turning off the water and draining any water from the expansion tank. Then close the tank air valve and turn the water back on. Expansion tanks with no bladder or ruptured bladder would need recalibration more often but not every day. Should the expansion tank refill (re-saturate) in a day or two, the expansion tank itself may have a leak and need to be replaced. An expansion tank that is below the pipe it is mounted on must have a good bladder to work correctly.

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secutanudu

Good point, i'm probably wrong about that....Let me get some pictures and I'll post back.

The water heater is ~2 yrs old, no odd sounds. Not sure if the old TP valve was used when the heater was replaced. There was no water in the bucket for 2 days, on the third day there was some water, so i doubt it was residual water from the old one.

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Andrew

secutanudu

I finally got around to making a diagram of all the water feeding the water heater and boiler...I am confused as to whether the expansion tank (which is old and rusted on the outside) is serving the boiler or water heater (or both???). Any ideas?

Attached Thumbnails

 

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Andrew

LateralConcepts

Where you say "this thing is over here" (with the purple arrow), that thing is a PRV or Pressure Reducing Valve. It should be in the line coming in from the meter before any other fixture. It has probably failed. Did you ever check your water pressure? Shouldn't be over 80psi.

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Alan

I wouldn't say the PRV would have anything to do with the T&P problem, since it's connected AFTER the water heater.

I would say his boiler system requires a lower pressure than whatever the incoming is, and the incoming isn't high enough to require a PRV on the main feed.

That being said : Have you checked the expansion tank yet? Unscrew the cap on the needle valve, and push down on the needle. Only air should come out. If you have water in it, then it needs to be replaced.

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Journeyman Plumber

secutanudu

There is another regulator right after the meter which is functional (not shown in my diagram). the house has about 50psi. Not sure why there is another regulator near the expansion tank.

Any idea whether the expansion tank is serving the boiler or water heater? I am confused...it looks like it is serving both to me.

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Andrew

Alan

The expansion tank IS serving both (unless the PRV has an internal check, which I doubt). Read my post above ^^^

The expansion tank should also be sized properly, and the pressure inside of it equal to the water pressure in the house.

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Journeyman Plumber

secutanudu

If the expansion tank is serving both...what prevents boiler water from co-mingling from the boiler to the water heater? The PRV is a watts, but the model # on the label is not visible anymore. I am trying to find it on the watts site, but can't find any PRV that looks like it (or backflow preventer for that matter).


Needle valve...is that what I labeled "air vent"?

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Andrew

secutanudu

I took off the cap on that air vent, pressed the needle, and water comes out.

You said "it" needs to be replaced...do you mean the air vent (needle valve?) or the expansion tank?

Also - when I replace either of them. I assume i need to turn off the boiler and drain some water to let the pressure out. Should I just switch off the boiler using the red switch at the top of the stairs? Should I also turn the valve off the gas line that feeds the boiler?

Thanks.

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Andrew

Alan

The needle valve is on the expansion tank. Not on the other device you've got in your drawing.

It's on the opposite end of where the tank connects to the water line.

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Journeyman Plumber

secutanudu

Found it - only air.

In other news...2 weeks after changing the valve, there is no longer water in the bucket. Maybe it's fixed...

Any answer to my earlier question regarding what prevents boiler and domestic water from mixing together?

Thanks for your help.

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Andrew