A look at why a gas boiler in Port Moody keeps losing pressure, and how a technician tracks down the actual source.
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Quick answer
A gas boiler that keeps losing pressure in a Port Moody home is usually leaking somewhere in the system, has a failing expansion tank, or has a faulty pressure relief valve — repeatedly topping up the pressure without finding the cause just delays a proper fix.
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A boiler losing a small amount of pressure once, after being freshly filled or bled, isn't unusual — air working its way out of the system in the days after a repair can cause a modest drop. What actually signals a problem is pressure that keeps dropping over weeks or months, needing the system topped up repeatedly. That pattern means water is leaving the system somewhere, or the expansion tank isn't doing its job of absorbing pressure changes as water heats and cools.
Finding a slow leak usually starts with a visual inspection of visible piping, joints, and the boiler itself for staining or mineral buildup, since even a small leak tends to leave a trace over time. If nothing is visible, a technician may pressure test sections of the system to isolate where pressure is being lost, particularly in homes with piping routed through walls or under floors where a leak isn't visible at all.
The expansion tank is checked separately, since a tank that's lost its air charge or failed internally won't show as an obvious leak but will still cause the system to lose pressure or run at unstable pressure over time.
Repeatedly adding fresh water to a leaking system isn't a fix — it introduces more dissolved oxygen into the system each time, which accelerates corrosion inside the boiler and piping over time. What starts as a small, manageable leak can turn into a bigger repair if the underlying cause is left unaddressed for a long stretch while pressure just gets topped up as a workaround.
Safety note
This job touches a gas-fired appliance and its venting. If you ever smell gas or suspect a carbon monoxide problem, get everyone out of the house first, then call FortisBC's emergency line at 1-800-663-9911 before you do anything else. Connecting, disconnecting, or servicing a natural gas water heater or boiler is licensed work; CANRO's techs hold Technical Safety BC gas licence LGA0043870 and boiler licence LBP0046450.
A small one-time drop after a fill or bleed isn't unusual, but pressure that keeps dropping over weeks or months points to a real leak or a failing expansion tank that needs to be found and fixed.
A slow leak somewhere in the piping or at a joint is the most common cause, though a failing expansion tank or a weeping pressure relief valve are also frequent culprits.
Original cast-iron radiator piping in older Moody Centre and Glenayre homes has had decades to develop pinhole leaks from gradual corrosion, which is more common there than in newer piping.
You can in the short term, but repeatedly refilling a leaking system introduces more dissolved oxygen each time, which speeds up internal corrosion — it's better to find and fix the actual leak.
By checking visible piping and joints first, then pressure testing sections of the system to isolate where pressure is being lost if nothing is visible, and checking the expansion tank separately.
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