Boiler is over pressure due to B & G pressure reducing valve


Old 12-05-17, 07:46 PM
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Boiler is over pressure due to B & G pressure reducing valve

Hello all.

The service contract I have has helped me weather my boiler (178,000 BTU) getting over pressure and releasing water via the pressure relief valve.

I have well water and my pump pressure switch is set to 30-50. The Peerless boiler is about 17 years old. The repair folks over four visits changed the pressure reducing valve, then the Extrol expansion tank from a 30 to a 60, then the aquastat, all the while bleeding the system here and there. The pressure relief valve was changed.

The problem: after a few days the boiler gets over pressure to about 30 lbs and water releases. The solution I have found is to shut the water feed valve off, release some water, and leave it alone. For two weeks it is perfect with 22 lbs of pressure for a basement zone, and first and second floor zones, plus a master bedroom zone. Hot water is electric. Turn on the water valve and within a day and a half, the pressure goes back up.

The repair people loosened the nut on the pressure reducing valve and counterclocked it so the screw on top of the valve is up high. Yet, the boiler pressure gets to 30-32 after a day or so, I have to shut the water valve off in the line before the pressure reducing valve, let out some water, and it all goes back to perfect.

The question: what could keep causing the system to get to 30-32 lbs pressure when the pressure reducing valve and other parts are new as in just a month? The reducing valve is adjusted to reduce pressure. What is going on? How is water getting through the reducing valve?

Last edited by PJmax; 12-05-17 at 08:19 PM. Reason: added some breaks to the text
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Old 12-05-17, 08:01 PM
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If the problem subsides when you turn the water off manually although the feed valve is new change it.
If it was anything else it would continue with the water shut off.

It may be new but it sounds like its defective.

Hope this helps a little.
Old 12-05-17, 08:20 PM
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I added some spacing to your text. Very hard to read one long paragraph.

I have to agree with spott. That valve is allowing the boiler to overfill.
Pretty rare to get a new defective valve but it does happen.
Old 12-06-17, 02:15 AM
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If the supply piping to the reducing valve is galvanized steel did the tech give it a good strong flush BEFORE installing the new reducing valve? If not, there could be particles of rust or other crap that damaged the seat in the new valve.

Here is a tip, keep the manual valve closed and monitor the pressure in the boiler on a regular basis. There is no need to have the water "turned on" except to make up for leaks in the system. I have run systems for years without the make-up water on.
Old 12-06-17, 09:44 AM
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There are many reasons why boiler water pressure rises above set point. Because boiler pressure reducing valve function is to control pressure the first thing to do is check it.

Turn off water feed to BPRV then drain some boiler water until desired pressure setting is reached. If after a few hours or overnight, pressure does not rise then BPRV is defective. If pressure does rise then problem is elsewhere. There may still be other issues but this is where to start.

BPRV valves are easy to clean. Disassemble the valve and clean out debris. The wire filter screen often cloggs or disintegrates. A replacement filter can be made from a coiled 3/4” strip of window screen.

Make it easy to remove valves without shutting down system by installing shut off valves and unions on either side of it.

Rust particles from the city water system are often cause of the problem. It helps to install a “whole house water filter” on the feed line to boiler and water heater. The type in the link below has a clear plastic body to see filter condition and built in valve with 3 positions, shut off for replacement, by pass and filter.

Last edited by doughess; 12-06-17 at 12:08 PM.

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