The pressure relief valve is the last line of defence against overpressure in a boiler, and on West Vancouver's older hydronic systems a dripping or seized valve needs prompt attention.
Tell us what you need—we’ll call you back fast.
Quick answer
A pressure relief valve (sometimes just called a relief valve) opens automatically to release water and pressure if a boiler system builds beyond a safe threshold, protecting the system from a dangerous overpressure event. It should never be capped, plugged, or ignored if it is dripping. On the older hydronic boilers still common in West Vancouver's character and mid-century homes, valves that have never been tested or replaced are one of the more overlooked safety items, and a technician will replace rather than attempt to reseat a valve that is leaking or has seized.
Need a licensed gas fitter for your hot water / boiler? Call CANRO at (604) 359-1081 — residential natural-gas heating and hot water across Metro Vancouver since 1999.
A closed hydronic heating loop is a sealed system: water expands as it heats, and something has to accommodate that expansion. An expansion tank normally absorbs it, but if the tank has failed, waterlogged, or the system pressure otherwise climbs too high, the relief valve is designed to open at a set pressure and discharge water through a drain line before a fitting, gasket, or the boiler's own pressure vessel is stressed beyond its limit.
This matters more than people expect in older West Vancouver homes with cast-iron radiators, where the total volume of water in the system is larger than in a modern low-mass hydronic setup, meaning more pressure builds if the expansion tank isn't doing its job.
A dripping relief valve is almost always a symptom of something else: a waterlogged expansion tank, a failed pressure-reducing valve on the makeup water feed, or scale buildup inside the valve seat that's preventing it from sealing fully. Capping, plugging, or otherwise defeating the valve to stop the drip removes the system's overpressure protection entirely, which is a serious safety hazard rather than a fix. The correct approach is to diagnose why it's discharging and address the root cause, then replace the valve itself if it's scaled, seized, or has been discharging long enough to damage its seat.
Soft North Shore reservoir water means scale buildup inside a relief valve tends to be slower than in areas on well water, but valves that have simply never been replaced over a couple of decades still seize from age and mineral crystallization at the seat.
On a boiler that is otherwise in good working order, replacing a relief valve is a routine, inexpensive safety item. But if a technician finds the relief valve has been discharging for a long time, there can be secondary corrosion around the boiler base or nearby framing that needs a closer look, particularly in older West Vancouver basements where moisture from a persistent drip has nowhere obvious to drain. In that situation the conversation shifts from just the valve to whether the surrounding system and boiler have been affected.
Safety note
Never cap, plug, or otherwise disable a pressure relief valve, even if it is dripping — it is a critical safety device against overpressure. Boiler and gas appliance work in BC must be performed by a Technical Safety BC licensed gas fitter. If you smell gas or suspect a combustion problem, leave the home and call FortisBC at 1-800-663-9911.
No. A drip means the valve is actively relieving pressure it shouldn't need to, which points to an underlying problem such as a failed expansion tank. It should be diagnosed and addressed, not ignored.
It's connected to a pressurized gas-fired boiler system, so replacement should be done by a licensed gas fitter who can also diagnose why the valve was discharging in the first place.
Higher heating demand means more heating cycles and more thermal expansion in the system, which can expose a marginal expansion tank or a valve nearing the end of its life more readily during cold weather.
Soft reservoir water does slow scale buildup compared to well water, but it doesn't eliminate the mechanical wear and age-related seizing that eventually affects any relief valve.
A relief valve on a boiler typically responds to pressure alone, while a T&P valve on a water heater responds to both temperature and pressure; they serve a similar overpressure-protection role on different equipment.
It's a good item to have checked during a regular boiler service visit, since a valve can seize from disuse just as easily as it can fail from overuse.
Family-run, TSBC-licensed (gas LGA0043870 · boiler LBP0046450), serving Metro Vancouver homes since 1999. Residential, natural gas only.
Call (604) 359-1081 Email info@canroheat.ca“Canro does an amazing job! Super professional and skilled with everything—boilers, furnaces, and AC. Always a pleasure working with them!”
“Five stars for Canro. We needed a replacement of a 30-year-old boiler. A new high-efficiency unit was installed—clean, professional work.”
“I can’t speak highly enough about George, who was recommended for a boiler service call for my parents’ home. George is excellent.”
25+ years keeping Metro Vancouver homes comfortable. Honest advice, upfront pricing, work that lasts.