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A few weeks ago, my oil-fired water boiler started continuously leaking water out of the pressure release valve on the top of the unit. I know this is leaking steadily because it drains into a 5gal bucket and I have dumped it twice now. I examined the system and determined that in order to keep leaking, water must be fed into the system from somewhere. So I looked up this Pressure Reducer Valve and determined its function - filling the system when water pressure gets low. I also read online that this valve can malfunction and let in too much water pressure causing this sort of leak.

My Pressure Reducer Valve is part number: Taco 329-3
Taco 329-3

I see screws... can this be opened and cleaned or should I replace this Pressure Reducing Valve entirely? Is there anything else I should check in my diagnostics?

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What is the pressure on your boiler's pressure gauge (often a combined temperature/pressure gauge)?

Several things could be wrong - replacing parts willy-nilly gets expensive.

If the pressure is below the relief valve setting, the relief valve may be faulty. If the pressure is at or above the relief valve setting, the pressure reducer may be faulty. If the temperature is too high, the relief valve may be a combined temperature/pressure relief which is actuating properly due to temperature extremes. The reason for any such temperature extremes should be corrected.

If you don't really have a solid understanding of what you are doing, a licensed boiler service technician can be well worth the cost of the service call.

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  • Pressure is 12.5 psi, temperature ranges from roughly 160 to 180 degrees. The pressure relief value only leaks for a short period of time after the boiler cycles on and the temperature approaches 180 degrees. The leak is a steady drip for a few minutes until it cools.
    – Layla Renee
    Commented Dec 6, 2013 at 23:45
  • That certainly points more towards the pressure relief (does it mention temperature, or not, or is it so corroded as to be unreadable?) than the pressure reducer - 12.5 is a happy boiler pressure and far below most house water pressure, so the PRV looks to be working just fine. That is generally a happy range for most hot water boilers, so probably a new relief valve is in order - be sure it matches the old one.
    – Ecnerwal
    Commented Dec 7, 2013 at 0:16
  • Thanks for the info! I did replace the relief valve last winter, so I figured it was ok but I guess it could have failed already.
    – Layla Renee
    Commented Dec 7, 2013 at 2:10
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I assume you have an expansion tank attached to the cold water line leading into the boiler. I’d check that – if it feels warm all around, it’s membrane is probably faulty and the tank needs to be replaced.

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