Pressure Relief Valve Leaking Water


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Old 10-14-12, 12:38 AM
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Pressure Relief Valve Leaking Water

Hi all,

I have a Weil-McLain WGO-4 Oil Boiler. Spec sheet I found is here. It was installed in 2001.

Last winter, we kept finding water on the floor in the furnace closet. We thought it was the hot water heater until I noticed it was dripping from the pressure relief valve. If I lift up on the manual relief, water would pour out. We had our oil supply company come out and replace the valve. Now, I don't know if they looked into why it was leaking in the first place, but this seemed to fix it. This was at the end of last winter, so after it got warm, the heat system wasn't used.

Now, heat has only been on a week or so and it is leaking at a good steady pace again.

What would cause this? Is there too much pressure? Currently, the system is on but the unit is off and the P/T gauge reads 145-F / 15-psi. I turned the stat up so it kicked on and the P/T gauge didn't change any.

Any ideas would be great.
 
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Old 10-14-12, 08:28 AM
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What is the setting on the PRV at which it opens?
 
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Old 10-14-12, 08:36 AM
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I lived with this problem for a few years, changed the pop valve a few times but it always leaked after a while. Finally I replaced the expansion tank with a slightly larger one and never had the leak again. I think these tanks can be adjusted by adding/removing air but I just replaced it anyway.
 
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Old 10-14-12, 09:43 AM
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Thanks for the input. Further research indicates that I have a newer diaphragm style expansion tank. It is connected directly to the hot water output of the boiler. I don't have a tire pressure gauge handy but pressing the pin in the valve has no hiss or any effect, so my guess is that it is at 0psi. Since, to my knowledge this has never been filled with air or ever maintained since 2001 (when installed), I am thinking this is the problem.

So, is this as easy as pumping 12psi (as indicated on the tank label) into the tank? Currently, the tank feels like the entire thing is filled with water. Will pumping in air push some of this water back out and put the tank back in its happy place?

The PRV is a 30psi valve. However, it doesn't seem like there is that much pressure anywhere in the system. I don't hear/feel any pressure release if I lift up on the lever on top of the PRV.
 
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Old 10-14-12, 10:17 AM
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I'm sure someone else with more knowledge will chime in but I would think you need to drain some water out before pressurizing and the auto fill valve would equalize things.
 
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Old 10-14-12, 10:51 AM
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Boiler pressure needs to be zero to check the air pressure in the expansion tank. Your pressure/temperature gauge may be toast.
 
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Old 10-14-12, 10:56 AM
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NEVER trust the pressure gauge on your boiler. The best way to check the pressure is with a water gauge on a female hose adapter. Put that on your boiler drain and then open the drain to check the pressure.
 
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Old 10-14-12, 10:47 PM
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Ok, so how do I get the boiler pressure to zero to check the expansion tank. Knocking on it sounds like it is full of water. There is no drain on the tank... the valve for air is on the bottom and pressing the pin in doesn't let air out and doesn't leak water. There is also no shutoff valve between the boiler and tank, only after the tank.

I was hoping to just put the air in the tank and everything work... but nothing is ever easy... or is it?
 
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Old 10-14-12, 11:50 PM
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Turn off the power and let the system cool to about 100 degrees. Turn off the supply water to the system and let out water from the boiler drain or any other drain until the pressure is zero. Don't let out any more water than necessary. If the gauge is shot it may never go to zero but the water draining will likely slow to a trickle rather quickly. Once you achieve zero pressure you can change the gauge (if necessary) by having the new gauge at the ready with the threads already prepped with Teflon tape and goo. Pull the old gauge with one hand and insert the new gauge with the other.

While the pressure is zero check the air pressure in the expansion tank and set it to 12-15 psi. With everything tight turn on the supply water and let the pressure stabilize. Turn on the power to the boiler.
 
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Old 10-15-12, 06:31 AM
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Thanks for the play by play.

I believe I have shutoff valves on the circulator pump side (return side) and after the expansion tank. Do I shut all off?
 
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Old 10-18-12, 11:15 PM
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Ok guys. Update.

I cooled the system for two days (not that cold yet here). I shut off the water supply and drained the boiler. I took out the gauge and it actually moved when I took it out. I cleaned it up and it seems fine.

I put 12psi of air in the expansion tank. It definitely had 0psi. As I added air, I could hear water being pushed out. Turned water supply back on, waited for pressure to reach 12psi on the gauge. Yay. But wait... the boiler drain valve is leaking. Crap. Abort!

I drained again.. and removed the drain valve. I disassemled as much as I could and soaked in vinegar. Loosened everything up. Rinsed a lot of crud out. Reassembled. Turned water back on. No leaks.. so far. Yay.

Now. Do I need to do anything specific to get the air out of the pipes? I currently have the water at 12psi. When I hear the water supply stop, I hook a hose up to each of the other water drain points before the circulators. When I hear the air and gurgling stop, I shut it off and then go to the next. Every once in a while, I release the pressure at the PRV. I currently have the burner power unhooked so it doesn't heat up on me yet.

I think my system is somewhat involved because this boiler is piped for dual zones. One of the circulators has two feeds off of it... or before it since the circulators are piped right before the return to the boiler.

Any other tips would be great. I don't see anything else I can tinker with.
 
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Old 01-09-13, 08:22 PM
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Hi all,

I am still having issues with this. Since my last post, everything has mostly been working. We ran out of oil a week ago or so and got the tank filled up. After that, I had an issue getting it back on. Had to bleed the oil. Not something I typically have to do.

Then, I noticed I am having water trickle out the PRV again. So, I cooled and drained the system and checked the pressure on the expansion tank again. 0psi. I added 12psi of air and filled it back up.

I shut off all of the return valves, set the lever on the reducing valve vertical to bypass, and then took a hose to each purge valve until no air bubbles into a bucket of water. I rotated between the three return valves almost a dozen times.

I just turned everything back on. Am I doing the procedures above correctly?

Now,

The PRV is relatively new... less than a year old. I don't suspect this needs replaced... or does it? When it drips, the PT gauge on the boiler reads around 15 psi, definitely not over 20 psi and certainly not at the 30 psi of the PRV.

Could the reducing valve be the issue? I can definitely see/hear it reduce when I move the lever between horizontal and vertical. I have one of these.

Or, is it more likely that my expansion tank needs replaced?
 
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Old 01-09-13, 08:33 PM
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If you had 0 psi in the tank then the bladder is leaking. Replace the exp tank
 
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Old 01-09-13, 08:36 PM
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I suspected...

Is this as simple as draining, unscrewing the tank and screwing in the new one?
 
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Old 01-09-13, 08:48 PM
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You don't have to drain the whole system, just take it to 0psi and have the new one ready to screw in (threads doped up already) You will probably have some water come out, but you can do it pretty quickly, just be ready for the weight of the old one.
 
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Old 01-09-13, 09:14 PM
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OK.. added to my to-do list.

Now, the tank I have definitely has 12 psi cushion, and the PRV is still dripping water. Not much, but still something. PT gauge shows 20 psi.

Could the tank still be causing this drip? My original research on this issue indicated that I was getting drip because the tank had 0psi and was water-logged. But now, it shouldn't be.

Is it possible that this PRV has been dripping so much it is sort of stuck open slightly?
 
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Old 01-09-13, 09:18 PM
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NEVER TRUST THE BOILER GAUGE FOR ACCURACY. I said that to you before, remember.... Also, once the relief valve opens it may never close properly again. Upon opening they tend to get sediment stuck in the seal. Replace the valve.

FYI, in the industry what we call a PRV is a pressure reducing valve. What you are calling a PRV is called a pressure relief valve or relief valve in the industry.
 
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Old 01-09-13, 09:41 PM
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Why aren't boiler gauges to be trusted? I just replaced it back around my October posts. If they can't be trusted, what good are they?

Figures there would be two common components with the same PRV acronym. Thanks for the clarification... although I started using PRV after seeing it abbreviated that way in some other posts.

Sediment is a good possibility here as I have well (extremely hard) water. I think I also need to replace the boiler drain valve as that opened up once and takes extreme torque to close and not drip. Getting a shopping list ready.
 
 

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