Boiler Pressure Keeps Dropping in Greater Vancouver

A boiler that needs regular pressure top-ups has a water loss problem. Closed hydronic systems should maintain pressure indefinitely without intervention — ongoing pressure drop means water is escaping somewhere.

What This Symptom Means

Pressure drop in a closed system is caused by water leaving the system. The rate of loss gives important clues: slow loss over weeks suggests a small seeping leak; rapid loss in hours suggests an active leak or PRV discharge.

Common Causes

• Pinhole leak in a pipe, fitting, or radiator
• Pressure relief valve discharging due to overpressure
• Expansion tank failed and PRV opening repeatedly during heating cycles
• Automatic air vent leaking water
• Drain valve at the boiler base partially open
• Boiler heat exchanger developing a small internal seep

What Homeowners Can Check Safely

• Note the rate of pressure loss — this information helps the technician narrow the search
• Walk through the home looking for water stains, damp carpet near baseboards, or visible corrosion on visible pipes
• Check whether the PRV discharge pipe drips during or after heating cycles

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.

• System pressure test with the fill valve closed to isolate where pressure is being lost
• Boiler heat exchanger pressure test if no external leak is found
• PRV and expansion tank inspection
• Pipe and fitting inspection in accessible locations
• Thermographic scan if leak is suspected in an inaccessible location

Frequently Asked Questions

Is it okay to keep adding water to a leaking boiler system?

Continually adding water is a temporary workaround, not a solution. Each water addition also adds dissolved oxygen and minerals to the system, accelerating internal corrosion. The leak source should be identified and repaired, both to protect system components and to stop the ongoing water loss.

My boiler loses pressure every few days. Where should I look first?

Start with visible components: the expansion tank (tap it to check if it sounds hollow), the pressure relief valve discharge pipe (check for moisture or staining), all visible pipe joints and radiator connections (look for white mineral deposits or rust staining indicating dried water), and the boiler drain valve. If no external leak is found, the heat exchanger needs professional testing.

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