Vaillant 190721 Pressure relief valve

This is a pressure relief valve supplied for Vaillant COMBIcompact combi boilers, listed under part number 190721. The valve sits on the heating circuit and opens when system pressure climbs past its set point, discharging water through the relief pipe to protect the boiler, seals and heat exchanger from over-pressurisation. It is offered as an aftermarket-compatible item and is also listed against the alternative numbers 190717 and 87167621440.

• Water continually dripping or running from the boiler's pressure relief discharge pipe when the system is cold.
• System pressure creeping up or falling away repeatedly, with the gauge reading high even after topping up or draining down.
• The valve weeping at the outlet connection, or scale and corrosion debris visible around the valve seat.
• Boiler locking out or cutting out on pressure-related faults after the heating circuit has been refilled.
• The valve spindle feels stiff, seized or fails to reseat when the system is brought back to normal pressure.

• Confirm the boiler model and the part number stamped or printed on the existing valve before ordering.
• Cross-check the alternative numbers 190717 and 87167621440 against the appliance's parts listing.
• Check whether a sealing washer or fibre gasket is required at the valve connection, as these are often reused from the old fitting.