Boiler pressure keeps dropping because the sealed system has a slow leak. A hydronic system should hold its pressure for years without being topped off. If the gauge creeps down week after week, water is escaping somewhere, most often at a weeping circulator seal, a relief valve discharging quietly into a floor drain, a waterlogged expansion tank, or a pinhole in a baseboard line behind finish work.
Where does the water go when boiler pressure keeps dropping?
In the buildings we work on around Ridgewood and Bushwick, it’s almost always one of four places: a weeping circulator pump seal, a relief valve dumping into the drain, a failed expansion tank, or a pinhole in a baseboard line buried behind finish work.
The relief valve is the one people miss. It discharges quietly into a floor drain, so there’s no puddle to find, just a gauge that keeps falling and a gas bill that keeps climbing.
When does low boiler pressure become urgent?
Low pressure on its own isn’t dangerous. A boiler short-cycling, banging, or locking out on low water is. If your unit is shutting down repeatedly in cold weather, stop topping it off and call. That’s a no-heat failure a day or two away, and no-heat calls are the ones we take at 3am.
What does a plumber do to find a boiler pressure leak?
We pressure-test the system, check the expansion tank charge, inspect the circulator and relief valve, and isolate zones to find which loop is losing water. Most of the time we find it in under an hour and fix it the same visit. See our full boiler and heating services for what’s covered.
How do you prevent boiler pressure from dropping next winter?
Annual boiler service catches these problems before heating season. We check the expansion tank pressure, inspect the circulator bearings, test the relief valve and look for early-stage leaks at the zone valves. An hour in September beats a 3am call in January.