• PRV dripping at relief port

    PRV dripping at relief port

    Quick Answer:

    A drip from the PRV relief or weep port usually means the system is seeing higher pressure than the valve is set for, there’s thermal expansion the system can’t absorb, or the valve’s internal diaphragm or seat has failed. First check the system gauge for high static pressure and verify the expansion tank charge and function. If cold static pressure is normal but the relief still drips, the PRV is likely damaged and should be replaced.

    Why This Happens

    The relief port is the valve’s safety outlet. It opens when pressure rises above the valve setpoint so water can discharge instead of over-pressurizing the system. Common causes:

    • Closed system thermal expansion when heating raises pressure and the system has no working expansion tank.
    • A valve that is jammed or not shutting to its setpoint—sometimes a PRV stuck high causing pressure spikes.
    • Internal wear, a torn diaphragm, or debris in the valve preventing a tight seal.

    Step-by-Step What to Do

    Step 1 — Observe when and how it drips

    • Note whether the drip is continuous or only when heating runs. Continuous drips suggest a failed valve or constant overpressure. Drips only during heating suggest thermal expansion.
    • Look at the amount: a few drops per hour versus a steady stream matters for urgency.

    Step 2 — Check the system gauge for static pressure

    • With the system cold and no water use, read the pressure gauge. This is the static pressure.
    • Compare it to the valve’s setpoint (often stamped on the body) or the normal system pressure. If static pressure is above normal, you have overpressure that must be corrected.
    • If you find unusually high supply pressure, reducing incoming pressure or adjusting the feed pressure regulator is required before replacing valves.

    Step 3 — Verify expansion tank charge and function

    • Shut off the fill/feed valve and relieve system pressure (open a faucet until flow stops).
    • Check the expansion tank air charge at the Schrader valve with a tire gauge. The tank’s precharge should match the system’s cold static pressure.
    • If the tank is waterlogged or air charge is low, refill to the correct precharge or replace the tank. A failed tank commonly causes pressure spikes that force the relief to drip.

    Step 4 — If pressure reads normal but the relief still drips

    • If the cold static pressure is within expected limits and the expansion tank is working, persistent dripping usually means internal valve failure — torn diaphragm, corroded seat, or trapped debris.
    • Don’t try prolonged repairs on a leaking relief port; replacing the PRV is the reliable fix. Before replacement, shut off the water feed and relieve pressure so you can work safely.
    • Also inspect for other leak types such as a PRV leaking from adjustment screw, which can point to a different repair or replacement need.

    What Not to Do

    • Don’t plug or cap the relief port; it’s a safety discharge path.
    • Don’t ignore a persistent drip; it can indicate system conditions that lead to bigger failures.
    • Don’t try to bypass or jury-rig the valve with makeshift parts or soldered caps—those actions remove the safety protection and can be dangerous and illegal in some areas.

    When to Call a Professional

    • Call a licensed plumber if you’re unsure how to isolate and depressurize the system safely or if replacing the PRV requires soldering or complex pipe work.
    • If pressure fluctuates rapidly or you see signs of major leaks, call a pro immediately.
    • If the system is a boiler, hydronic heating, or a gas-fired water heater and you’re not comfortable working on those systems, let a professional handle it.

    Safety Notes

    • Always relieve system pressure before touching or removing the PRV. Open a faucet to drop pressure and wear eye protection and gloves.
    • Hot water can scald; cool the system or wait until it is safe to work on components near the heater or boiler.
    • Do not cap or block the relief port under any circumstance—doing so removes a vital safety function.

    Common Homeowner Questions

    • Why does it only drip when the system heats up?
      Thermal expansion raises pressure; a bad or missing expansion tank lets pressure rise enough to open the relief port.
    • Can I stop the leak by tightening the valve?
      No. A persistent drip usually indicates internal wear or a torn diaphragm; tightening won’t fix it and can damage the valve.
    • Is it safe to cap the relief port until help arrives?
      No. Never cap the relief port; it’s a safety device and must remain able to discharge.