Boiler Losing Pressure in Greater Vancouver

A boiler that repeatedly loses pressure is one of the most common service calls in Greater Vancouver homes with hydronic heating — and the cause can range from a simple bleed procedure to a system leak requiring repair.

What This Symptom Means

Boiler systems are closed loops that should maintain pressure between 12–18 psi when cold. Pressure that drops over days or weeks indicates water is leaving the system somewhere — through a leak, the pressure relief valve, or excessive bleeding.

Common Causes

• Slow leak at a pipe fitting, radiator connection, or valve body
• Pressure relief valve weeping — discharging small amounts of water to drain
• Expansion tank failed — waterlogged tank causes relief valve to open during heating
• Air bleeding removing more water than expected during bleed procedure
• Automatic air vent leaking water
• Boiler heat exchanger developing a small internal leak

What Homeowners Can Check Safely

• Check the system pressure gauge — note whether pressure loss happens slowly over days or drops rapidly during a single heating cycle
• Inspect visible pipes, radiator connections, and the boiler body for signs of moisture or staining
• Check if the pressure relief valve discharge pipe drips when the system heats up

When to Call a Licensed Technician

Boiler systems involve pressurized hot water, gas, and electrical components. Do not attempt to open sealed components, adjust gas pressure, or bypass safety controls without professional diagnosis.

• Pressure test to locate hidden leaks
• Expansion tank inspection, draining, and recharging or replacement
• Pressure relief valve replacement if weeping
• Heat exchanger pressure test if internal leak is suspected
• System re-pressurization and leak verification

Frequently Asked Questions

How do I add water to my boiler system to restore pressure?

Most boiler systems have a fill valve (also called a feed water valve) — a small valve connected to the cold water supply line, usually near the boiler. Opening it slowly allows water to enter and raises system pressure. Add water slowly, watching the gauge, and stop at 12–15 psi. If pressure drops again within days, there is an active leak that needs repair.

Is it normal for a boiler to lose some pressure over time?

A very small amount of pressure loss over months (a few psi) can occur in any closed system due to minor air release. Needing to add water more than once every 6 months suggests a leak or a failed expansion tank. Needing to add water monthly means there is a confirmed problem that should be diagnosed.

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