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Old 12-07-2010, 03:05 PM   #1
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Water leaking from boiler pressure relief valve

I have water dripping from the copper pipe coming from the expansion tank pressure relief valve and it has been like this since the boiler was new about 4 years ago. Since yesterday afternoon, it filled the five gallon paint bucket about 1-2 inches. I had the oil burner company here and they tell me my expansion tank is bad and that they replace the valve and the tank at the same time. If you knock on the tank it appears by the sound of it to be about 1/2 full... Can someone tell me if this makes sense...does the tank go bad or does it just need to be drained as I have read on some other posts? Also, is it possible just the valve is bad?


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Old 12-07-2010, 03:52 PM   #2
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If it's been leaking since new, I'd say you have an issue or two. One would be why it wasn't addressed at the point of installation. The second would indicate the expansion tank was too small to begin with.


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Old 12-07-2010, 05:00 PM   #3
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When the valve is leaking what is the pressure gage on the front of the boiler reading, how many pounds and what is the temperature.
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Old 12-07-2010, 08:47 PM   #4
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Are you certain that is a pressure relief valve on the expansion tank? I have a boiler and an expansion tank, however the pressure relief valve is on the boiler, which I think is typical. The expansion tank on my system is the older style horizontal tank mounted on the ceiling.

This type of tank has NO bladder, under normal conditions it is approximately half full of water, the rest is air. There is a drain valve on my tank, this is not a pressure relief valve, the purpose is to drain the water out of the tank if the tank becomes full of water. You do this by shutting off the boiler connection to the tank at the boiler, then you open the drain valve on the expansion tank, and drain out the water. The expansion tank drain valve also lets air into the tank to replace the water.

If this is what you have, then perhaps the valve is simply leaky, could have been defective from the beginning.
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Old 12-10-2010, 12:06 PM   #5
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so now which one is lieaking your drain valve or pressure releif valve? there is no pressure releif valve on the expansion tank. but if the expansion tank is to small then when the water heats up it compress's the air in the tank. if it to small then the extra pressure goes out the pressure releif valve. and if your drain valve is leaking then the valve maybe bad or theres something stuck in it
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