Gas boiler pressure too high

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Old 12-11-13, 10:03 AM
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Gas boiler pressure too high

Hi, I have a very old gas boiler (50 plus years) with a steel expansion tank. I had a backflow preventer installed in May as there was not one at all. The PRV leaks occasionally when the pressure on my boiler reaches 30psi. I called the plumber and he drained the expansion tank. One week later it is leaking again. The pressure only rises when the unit is called for heat. #1 Do I need a new expansion tank? #2 could the back flow preventer have anything to do with this? #3 is there anything else that could cause the pressure to rise so high? thanks for your help.
 
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Old 12-11-13, 10:14 AM
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Possibly the fill valve is leaking... But the pressure would be hi all the time and just continue to rise until the relief valve trips...

The expansion tank needs to be emptied completely... Possibly the tech did not do this... This is probably the cause. Often it may seem like the tank is empty, when indeed it is not...

Call him back.. You paid for a service and you still have issues... He should correct it....

Pics of the boiler will help....
 
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Old 12-11-13, 01:27 PM
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tech came back and drained the tank again. lots of particles came out toward the end. he turned off the feed valve and said that if the pressure rises again then the expansion tank has a leak. when we bought the house we noticed that the expansion tank had a towel and plastic wrapped around the valve. if it has a leak would that cause the pressure to rise in the boiler?
 
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Old 12-11-13, 01:36 PM
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You would see water if there was a leak....
 
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Old 12-11-13, 01:53 PM
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that's what i thought. is it safe to have the feed valve off? there will be no more new water feeding into the boiler, correct? thanks for your time.
 
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Old 12-11-13, 02:35 PM
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is it safe to have the feed valve off? there will be no more new water feeding into the boiler, correct?
Yes and yes.... And with the valve off and if there was a leak you would have 0 psi in a short amount of time....

Starting cold pressure should be 12-15 psi...
 
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Old 12-11-13, 05:20 PM
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is it safe to have the feed valve off?
if there was a leak you would have 0 psi in a short amount of time....
So with that valve turned off it's very important to keep a close watch on the pressure gauge.
 
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