Leaking blowoff valve

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Old 02-25-11, 03:58 PM
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Leaking blowoff valve

I am chasing down a VERY sporadic leak through my blowout valve (30psi) for a year or so. It will usually leak every 1 to 3 weeks from a few drops to a few tablespoon . I check the pressure 2 or 3 times a day and it has been consistently at 20 PSI hot, never higher. The valve was replaced last year (It would not fully close after the first blowout) and the expansion tank pressure was checked and adjusted properly a few months ago at my yearly, The guy that checked it said it was a little low. I did not drain and check yet. Here is the question. If the tank pressure was low/ tank going bad would/could it be such a sporadic leak. If the pressure is getting high and the blow off is blowing what could cause it so sporadically and for that very small amount especially if I never see it above 20 psi.
 
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Old 02-25-11, 04:11 PM
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The gauge may not be accurate. It may be something different then 20psi.

What is the temp? High temps make relief valve trip also. 250 F

Did they install the correct relief valve? Whats it say on the tag? I have seen hany men put HWH relief valve on a boiler..Uggg.

If the expansion tank goes it will cause a higher pressure from thermal expansion with no where to go.

If it blew off once, and since its new, possibly a peice of sediment is caught up in there. You could try lifting it to let some water out to flush it. Do it when the boiler is at its coolest.

If it still leaks change it but make sure pressure is accurate.

Be careful though the water will be hot.

Mike NJ
 
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Old 02-25-11, 04:52 PM
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It is a Watts model M1 30 psi. The water temp is 175 or so never hotter. I am pretty sure, but not 100% that the service guy checked the gauge accuracy. I know I asked him to, because I read it on here. :O)
So am I correct to assume it is probably not the tank. I would hate to drain the system to check, because there is coolant in it and I have a few pipes on outside walls I would hate to dilute it more.
Could a piece of sediment cause a sporadic leak like I have or wouldn't it leak a little bit all the time?

Also is there a way to make an adapter for a gauge to be screwed onto spigot. That way you could easily check pressure/temp several times a year. Just a thought.
 
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Old 02-25-11, 05:16 PM
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Yeah, I'm down with the bad gauge... everybody here knows how I love to hate gauges...

I made one like this outta bunch of parts in the garage... you can get as fancy as ya like.

 
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Old 02-27-11, 04:59 PM
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Well I let the temp go down and opened the valve for like 2 seconds. Made a funky gauge like Trooper and the pressure is same as the gauge on the boiler. Had about 2 tablespoons leak out yesterday and then 2 tablespoons leak out today. Again pressure never higher than 20 and temp never higher than 180. Even though the valve is like a year old is that the next step. Is there anything else that could cause such a small leak??? Could a defective valve act like this????
 
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Old 02-27-11, 05:35 PM
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Are you there to actually witness the pressure at 20 when the valve opens? Or, are you seeing the water in the bucket at some later time... in other words, is it possible that the pressure is creeping up to 30 when you aren't there to witness?

I suppose the valve could be leaking... try this: open the relief valve full blast for a few secs, and let go the handle and let is 'snap' shut. See if that helps.
 
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Old 02-27-11, 05:44 PM
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I never witness the valve blowing off. I just keep a jar under the pipe. I would assume much more water would leak off to discharge 10 psi than 2 table spoons. Most that's ever came out has been a cup or less. I tried opening the valve like that on Friday night and for the first time in a while it has leaked 2 days in a row. I did not let it snap shut though just sort of let it down. I will try to let it snap tomorrow, the boiler is usually pretty cool when I get home as I turn the t stat down.
 
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Old 02-27-11, 07:38 PM
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Change the relief valve.

Mike NJ
 
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