Water Pressure Reducing Valve - Signs of Failure ?

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Chefwong

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Just short of increased city water pressure, I've noticed lately, water has been slowly coming out of the water PRV that is tied in front of the water feeding out heating boiler unit. Over past years, there's been water, but it seems like water is coming out of the PRV almost everyday. Not alot, maybe 2-3 qts I suppose.

Might need to actually benchmark this and see how much volume per day it's coming.

Anyhow, definately enough for me to notice...

What are the tell-tale signs a WPRV is failing ?
 

Matt Chesmore

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Not an expert but for clarification. Is the PRV on the makeup water of the boiler? I ask cause I wouldn't think city pressure would have anything to do with a closed boiler system. Boiler pressure should be regulated by a expansion tank. Anyway, if it is on the makeup water then I would say it is on it's way out. Are you sure it is a PRV valve and not a a RPZ(reduced pressure zone) valve? RPZ's are designed to "leak" if a reduced pressure exists. It provides a total air gap thus preventing backflow into the supply water system.
 

Dj2

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Acceptable residential water pressure is 40 to 80 PSI.

Get yourself a water pressure gauge and measure the pressure around your house - at the garden hos bibb, washing machine cold water supply, water heater drain. Do multiple checkings, and if you consistently get higher than normal readings, it's time to replace the PRV. Check faucets for drips. If you have an expansion tank, look for drips there too.
 

Chefwong

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The PRV installed is only inline right before it feed the heating boiler.
No PRV off the incoming main.

There is a expansion tank. I used to open it yearly and drain it.
Then I recall reading not to do it.
Might as well ask - is one supposed to drain the tank ?
 

Matt Chesmore

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hmm, Have you noticed increased pressure at other fixtures? I'm betting its just getting worn out. If you have naturally high water pressure(close to tower is one way that I know you can get high pressure) you should have 1 or 2 PRV's at the main supply to the house. Possibly it went bad also. Checking your pressure as stated is the only way for sure to know what your pressure is.
 

Matt Chesmore

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The PRV installed is only inline right before it feed the heating boiler.
No PRV off the incoming main.

There is a expansion tank. I used to open it yearly and drain it.
Then I recall reading not to do it.
Might as well ask - is one supposed to drain the tank ?
Doesn't hurt anything to drain and maintain the tank yearly.Especially in the fall before you put the boiler into use. It evacuate sediement that has built up over the summer months, just make sure it is pressurized correctly after your done
 

Matt Chesmore

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Doesn't hurt anything to drain and maintain the tank yearly.Especially in the fall before you put the boiler into use. It evacuate sediement that has built up over the summer months, just make sure it is pressurized correctly after your done
Let me say that tenderly, The expansion and compression of the bladder inside is what will make it fail. Reducing all the pressure on the tank thus a full expansion of the bladder, then a compression back to working pressure may make it fail. I am one that would rather find out that it has failed sooner then later, so I say maintain it and it will last as long as it ever was going to, but it is your call.
 

Chefwong

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Just for clarity.....the expansion tank I'm guessing is around 70-80 years old. Came with this brownstone...
I don't think it has a bladder inside.
 

Matt Chesmore

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Not that it matters, but what type of boiler do you have: ie hot water or steam. I still think the PRV is just worn out. I would think you could pick one up for less than $100.00 usd. If you have to hire a plumber to install it you'll add labor so you probably could double that in my part of the world.
 

Chefwong

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Hot Water

I've yet to google it, but if a PRV fails, could it potentially be a ~open valve~ and just literally, let a continuous flow out...
 

Matt Chesmore

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In essence, yes, and possibly at a high gpm rate. But this is wearing out, so it should start slow then pick up as it wears further eventually to a point were the PRV component has complete failure, this could even be a catastrophic failure and bloom, water everywhere.
AND now for the biggy. Hot Water Boilers are not something to be messing around with. If it was to run dry due to make up water not working correctly you'll be talking big $$$$ to probably replace. And by big money I mean for example we just replace one in a home with a HE model and the ticket was over $8000.00.
 

Chefwong

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Going to have to get up on a ladder and take a better look
There are 2 PRV's ? installed back to back inline before it hits the boiler

The one closest inline towards the boiler side has the discharge on it.
The one before it does not. Not sure the rhyme or reasoning to have 2
 

Jadnashua

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The nomenclature can be somewhat confusing...a valve discharging water is more the indication of a pressure relieve valve than a pressure reduction valve. They do different things.

A pressure relief valve just literally opens up to relieve excess pressure above it's setting (some are adjustable, some are not).

A pressure reduction valve should never leak unless it has a fault. It reduces the pressure from the supply, to some lower pressure you configure on its outlet. When those fail, they generally do not leak, but allow their outlet pressure to rise, or reduce the flow.

Sometimes, people will put a pressure relief valve after a pressure reduction valve, to help protect things, if the PRV fails. Normally, the relief valve would never open up. If you have that situation (and it sounds like you do), it is an indication that the first device - a pressure reduction valve - has failed. The pressure relief valve may just be doing what it is supposed to do. It can also be an indication of a failed bladder or expansion tank. Older expansion tanks DID need to be drained periodically, as the water moving through them would absorb the air used as the 'cushion'. You really do not want to use one of those on a heating system, as adding air means the opportunity for things to rust. With a bladder type expansion tank, there should be no air in the system that touches the water, and once any that is there dissolved in the fill water is used up (by rusting things!), it becomes essentially quite inert.
 

Matt Chesmore

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Here we call a pressure relief valve a T&P valve, short for Temp. and Pressure relief. T&P valves will and do drip the older they get. They basically lose there strength to hold pressure back and therefore leak through. Same thing though, if it goes bad suddenly then you have a straight open line. BTY DO NOT pull the little tab on top to try and re-seat the valve, unless your prepared to replace it :). It's been my experience that if it is dripping there's not much fixing to it, just replace it.

I have seen 2 pressure reducing valves inline back to back. This was in AR where they had very high municipal water pressure. They installed 2 for safety reasons, basically a back up in case one failed. How would one know if only one failed is beyond me, but that was the reasoning for them.
Air in a sealed boiler system is a bad thing, as has been mentioned, in fact there should be a air eliminator (spirovent) for just this reason.

Maybe a photo of what you have could explain things better to us.
 

Chefwong

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I think we may be on to something.....

So far, last 2 days, it's been warm enough that the boiler has not cycled on.
And sofar, no water in the bucket.
Prior to that, the unit has just mainly cycled in the morning.

I basically put a bucket under the discharge and have been eyeballing it in the morning and in the late evening to trend and observe any patterns...
 

Matt Chesmore

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Well I hate to state the obvious but, since we know your on the superhighway, Google a pic of a T&P and then A PRV and tell us which one is leaking. They have obvious visible differences, but they both have sort of a manual release lever on top, so don't come back with, well its kindof round with a lever on top. Please do your own research so that someone here can point you in the right direction. Sorry to be harsh but from what you have explained so far, it could be either.
 

Chefwong

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PRV is the only one that has a discharge coming off it.....and that is one I have the bucket under right now.

It looks like this

incoming line feed-T&P-nipple-PRV-downstream into the boiler
 

Chefwong

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With the bucket in place, it looks like water is discharging out of the PRV when the boiler is in use/cycled. I would say anywhere from 2cups-quart each time. Thoughts in next steps ? Root cause of the discharge
 

Jadnashua

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A T&P valve is typically used on a water heater and will open if either the temperature exceeds its setting OR the pressure does. A boiler would likely have one as well. A pressure relief valve can be used numerous places, but is a safety device that is not expected to open (nor is a T&P valve expected to open except in an error or fault condition).

Most people refer to a pressure reduction valve as a PRV, and those do not generally leak unless they're broken! Those are designed to literally reduce the pressure from their inlet side to their outlet.

A T&P valve and maybe a pressure reduction valve will usually have a test lever to verify that they can open...a PRV will not (it does usually have a bolt that can adjust the output pressure level, but no place where it would leak out during normal operation).

If you have a closed system and do not have an expansion tank, or that tank is not sized properly, or is defective, or it is not precharged properly, or is not installed where it should be, the safety valve could open while the system is heating. On a WH, that's typically at about 150psi. On a boiler, it is usually around 30psi. On a pressure relief valve, it's wherever it is adjusted (which may not be user adjustable, but is set at the factory).

All of those valves can fail, and there is more than one failure mode resulting in different symptoms.
 
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