M335M2 Male Pressure Relief Valve Opens

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  #1  
Old 04-28-19, 08:07 AM
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M335M2 Male Pressure Relief Valve Opens

Hello, I have a Well Mclain Gold boiler with a Watts 0342692 - M335M2, 3/4" Male Pressure Relief Valve. It leaks a little out of the drain pipe connected to it but it seems it's releasing every so often and I get water all over and then the boiler low water light comes on. After that the boiler will not kick on unless I cycle it on and off. I took out the low water sensor and wipe it down but I'm thinking I'll replace the relief valve first. I found it on Amazon for $15.88.

My question is, do you think its just the a bad relief valve or an underlying issue or pressure build up? What should I check?
 
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Old 04-28-19, 08:35 AM
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Does it only leak when the boiler is heating ?
What is the system pressure during operation ?

It should be in the 15-22 psi range. If it's approaching 30 psi then you need to address the expansion tank. It may be water logged or not have enough air in it.
 
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Old 05-09-19, 05:48 AM
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It started happening more often. The valve is a 30psi but the pressure gauge on the boiler reads almost 40 when operating. If I release the valve manually, the pressure goes back down but builds back up when its operating. I have a gray pressure tank, should I check that? What causes it to build pressure past 40? There is also another valve up top by the pressure tank that allows water into the system. If I release that the pressure builds. I was thinking maybe that's allowing water into the system increasing pressure?

EDIT: The pressure tank has a valve on the bottom and seems like there's no pressure at all in there. I was also watching a video and saw that the tank should be warm up top vs bottom and hollow sounding when tapping where the diaphragm separates air/water.

https://www.youtube.com/watch?v=1RCPrzjcIz4
 

Last edited by ajmboy; 05-09-19 at 06:03 AM.
  #4  
Old 05-09-19, 07:16 AM
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If pressure is building up , expansion tank is most likely water logged, as mentioned by Pjmax.
You have to replace the tank and prv.
 
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Old 05-09-19, 08:51 AM
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Ok, question though...if water logged does that mean its full of water? Because it feels empty. But maybe its actually full? No pressure, air or water release when depressing the air valve on the bottom of the tank. So putting air pressure in there would not do anything, correct? I already replaced the PRV.
 
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Old 05-09-19, 09:55 AM
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you can check the pressure , if it reads zero then definitely , it's full of water. if it gives any other reading then probably the rubber diaphragm is still in tact and it's still good.
 
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Old 05-09-19, 11:02 AM
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a,
That tank should be charged to at least 12spi. You can check the tanks pressure with an air pressure gauge. In order to check or charge the tank correctly it must be isolated from the system.

If you tap the tank when the boiler is cold the top should sound solid and the bottom tinny. There should be some water in the top and the air bladder in the bottom which accounts for the different sounds.

After you tap it cold then run your boiler up to temp and tap it again. If the tank sounds solid throughout then the bladder is either gone or needs a charge. Either way it must be repaired or replaced.

Why your boiler builds pressure with a defective tank it is because the heated water has no place to go when it expands just like a car radiator needs the overflow tank or it will overheat due to excessive pressure.

A lot of times it's just the tank and not the relief valve that is defective. The relief is just doing its job going off at the rated pressure. If the relief valve stops leaking when the pressure drops there is good chance the PRV is good .

You also mentioned the auto feed valve which also could be the problem if it continues to leak by constantly feeding the boiler until the relief valve goes off. To check this you can simply shut off your manual cold water valve to the boiler which will stop unwanted feeding and if the problem remains the same that will eliminate the feeder and concentrate on the tank.

Hope this helps a little.
 
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Old 05-10-19, 03:51 PM
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Thank you everyone for your responses, turned out it was full of water. I removed it and replaced with a tank I bought at lowes https://www.lowes.com/pd/Water-Worke...Tank/999971156

Came pre-charged at 13 psi. Can I leave it there or does the air pressure need to be higher?
 
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Old 05-10-19, 04:14 PM
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In a perfect world the tank pressure should match the cold operating pressure but you seldom see it and what you have is fine.

Thanks for the update.
 
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Old 05-10-19, 04:23 PM
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Another question, fired it up and while running the pressure gauge was reaching close to 40PSI. After it shut down, I released some water out of the PRV and its sitting at like 22. What's the correct procedure after installation? I'm sure it'll probably just build back up when it runs again.
 
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Old 05-10-19, 04:47 PM
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Depends what you had to drain to replace it. After you have installed, pressurized and bled the system if need be there is no procedure to follow. If operating properly that pressure should not fluctuate more than a couple of pounds from cold to hot.

I will say that I've never heard of that brand of tank and cannot find any specs on it. If it is too small in capacity it will not work. If you have NO cast iron rads, just baseboard, you need a #30 that holds 4.5 gals of water and I can't find the tanks specs.

Example of name brand tanks.

https://www.supplyhouse.com/Expansion-Tanks-353000
 

Last edited by spott; 05-10-19 at 05:02 PM.
  #12  
Old 05-10-19, 07:13 PM
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Old 05-11-19, 08:09 AM
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If that is the tank you have that's fine but be aware they do make different sizes.
 
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