Water Heater Pressure Relief Valve Greater Vancouver

The temperature and pressure relief valve (T&P valve) on a hot water tank is a critical safety device — understanding its function prevents both complacency about dripping and unnecessary alarm about normal operation.

What This Means

The T&P valve is a spring-loaded safety valve that opens automatically if tank temperature exceeds 99 degrees Celsius or pressure exceeds 150 psi. It prevents the tank from building to dangerous pressure levels. A dripping T&P valve is a signal that something in the system is not right.

Common Causes

• Continuous dripping: thermal expansion in a closed system (most common in Greater Vancouver homes with backflow preventers); T&P valve set point lower than system operating pressure; valve seat corroded or contaminated and not sealing fully
• Valve discharge after service: normal — a briefly opened T&P valve may drip until the seat reseats
• Old valve: T&P valves that have never been tested may fail open or may not open when needed; test by briefly lifting the lever annually

What Homeowners Can Check Safely

• Do not block or cap the T&P valve discharge pipe — this is a safety device
• Note whether dripping is continuous or only during hot water heating cycles (expansion dripping is intermittent)

When to Call a Licensed Technician

Water heater work involves gas lines, high-voltage wiring, and pressurized plumbing. Always call a licensed gas fitter or plumber for repairs beyond basic visual checks.

• T&P valve replacement — typical interval is every 5 to 6 years or when it starts dripping
• Expansion tank installation if thermal expansion is causing intermittent T&P dripping in a closed system
• System pressure check

Frequently Asked Questions

My T&P valve is dripping. Is that dangerous?

A dripping T&P valve should not be ignored. It is either: (1) doing its job and relieving actual overpressure — which means a system problem needs investigation; or (2) the valve itself has a worn seat and is leaking past the seat at normal pressure. Neither condition is safe to leave permanently. If the dripping is consistent and the water heater is set to the normal temperature, an expansion tank issue or pressure regulator issue is likely the cause.

How do I test my T&P valve?

Lift the lever briefly (1 to 2 seconds) and release. You should hear/feel water flow through the discharge pipe and then stop when you release. If the valve does not flow when lifted, it is seized and must be replaced. If it flows but does not stop when released, the seat is contaminated — often a flush and reseat resolves this, but replacement may be needed. Test annually.

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