Water dripping from pressure relief valve

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  #1  
Old 10-15-15, 07:17 PM
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Angry Water dripping from pressure relief valve

Hi all,

Yes, water dripping about half gallon a day out of the PRV, on typical hydronic system (I can attach pics). I've been through these forums enough to know about both the PRV itself and the expansion tank.

I've replaced both. I thought I had it licked given that the expansion tank inflation schrader valve seemed a bit leaky and rusty, and the PRV looked to be in rough shape too.

But the exact same behavior came back. It takes about a day to start dripping again, when the heat has been firing.

Typically the system seems to run at 20 PSI hot according to the gage.

Potentially related info: Over the summer, we did minor renovations to the house that required removal of two small baseboards in the kitchen. A plumber removed them. We also replaced a failed hot water heater, and the new one started leaking apparently due to the pressure in the house being too high. So we lowered that (cannot recall from what to what, but I know the pressure in the showers upstairs is kinda lame now, and the hot water heater is fine).

Could it be the filler valve? I just dont get it. Frustrating!

Thanks in advance for any advice.
 
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Old 10-16-15, 02:05 PM
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Could it be the filler valve?
Yes, it could be. There should be a manual shutoff valve ahead of the automatic fill valve (pressure reducing valve). Temporarily shut the manual valve and drain enough water to get the pressure down to about 15 psi with the system cold. If that seems to correct the problem, then replace the auto fill valve.

Also, I suspect that your boiler gauge may not be reading correctly.
 
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Old 10-16-15, 02:24 PM
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Typically the system seems to run at 20 PSI hot according to the gage.
For starters, don't trust the gauge, read this:

http://www.doityourself.com/forum/bo...ure-gauge.html

While you're at it, read this:

http://www.doityourself.com/forum/bo...sion-tank.html

Could it be the filler valve?
If you don't FLUSH THE LINE that leads to the valve, the crap from the pipe gets into the new valve and it leaks also.

We also replaced a failed hot water heater, and the new one started leaking apparently due to the pressure in the house being too high. So we lowered that (cannot recall from what to what, but I know the pressure in the showers upstairs is kinda lame now, and the hot water heater is fine).
You probably need an expansion tank on the domestic water heater also.
 
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Old 10-19-15, 05:59 AM
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Will try

Thanks for the suggestions, will check the pressure and a few other things.

I do see that the plumber also apparently replaced the PRV over the summer as well, though not sure why.
 
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Old 10-19-15, 06:27 AM
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replaced the PRV over the summer as well, though not sure why.
There are two valves with the same initials, so need to know which one you mean.

PRV can mean either:

Pressure RELIEF Valve, which is your safety valve that opens if the pressure gets too high,

Or, your Pressure REDUCING Valve, which is also known as your FILL VALVE, Automatic fill valve, etc...

Replacing a Pressure RELIEF Valve is good practice every 5 years or so.
 
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Old 10-21-15, 10:12 AM
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I meant pressure reducing.

I wish I had started with verifying the pressure gauge. You were correct, it was INCORRECT. It pretty much reads either 20 or 0. But, when dripping, a better gauge read 30, which makes perfect sense, given I had just replaced the relief valve.

So last night I simply turned down (unscrewed) the pressure Reducing valve so that the drain valve went from 20 to 15 cold.

This morning, hot, its at 25, no drip. I hope this fixes it.

I assume that, in a day or so, if its dripping again and at 30, the reducing valve has an issue.

Thanks
 
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Old 10-21-15, 04:32 PM
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Good deal... hope you're good to go now.

If you do have the bladder type tank that's discussed in that post I linked to earlier, it's a good idea to do the service to recharge it.
 
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Old 10-21-15, 07:49 PM
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Well that didn't take long. Dripping again.

I already replaced the expansion tank, which I checked and was at 12.5 going in, so should be good.

Should I assume its a faulty reducing valve?

Perhaps I could shut off the supply for a few days and be sure?
 
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Old 10-21-15, 08:00 PM
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Should I assume its a faulty reducing valve?
No, there's a well worn out cliche that goes alone with assume and I'm not going to repeat it!

Perhaps I could shut off the supply for a few days and be sure?
Yes. That's diagnostic.

Let the boiler cool, set the pressure to 15 PSI and close that valve.

Check gauge regularly.
 
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Old 11-23-15, 04:05 PM
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Just to confirm all this, yes, it was the Reducing Valve. I shut off the feed, had no issues for a few days. Replaced, and all is well.

Part of what threw me here is that it was replaced over the summer. I presume it was faulty.

All good now. THANKS TO ALL for the excellent support!
 
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Old 11-23-15, 07:17 PM
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Part of what threw me here is that it was replaced over the summer. I presume it was faulty
Since very little water ever flows in the line to the boiler, what happens is that 'crud' deposits in that line. Then, when the valve is changed and the line is not FORCEFULLY FLUSHED, that 'crud' breaks loose and finds it's way under the seat of the brand new valve, trashing it.

It doesn't seem to be standard practice to REALLY FLUSH that line when a valve is replaced, but it should be!

Glad it's all good now, happy heating!
 
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