Why Is My Boiler Losing Pressure?

A hydronic heating system or boiler that keeps losing pressure is telling you something: water is leaving the closed loop. The question is where — a boiler component, or a hidden leak in the piping. Here's how to think about it, Utah-style.

First: the boiler itself

Before hunting hidden leaks, check the usual boiler-side suspects: the pressure relief valve (discharging?), the expansion vessel (lost its charge?), visible weeping at fittings, and the condensate arrangement. A heating technician should rule these out — if the boiler checks clean and pressure still falls, the leak is in the distribution piping.

The hidden-leak pattern

A system that needs topping up regularly — weekly, monthly — with no visible water anywhere has a leak in the loop: under-slab radiant tubing, piping inside walls, or buried runs to outbuildings or snowmelt zones. The water escapes where you can't see it, which is exactly why pressure keeps falling with nothing to show for it.

Why it matters beyond comfort

Every top-up introduces fresh, oxygenated water into a system designed to run on treated, deoxygenated water. That oxygen corrodes radiators, tubing, and boiler components from the inside — so a small leak causes compounding damage over time. Finding it isn't just about the pressure gauge; it's about the system's lifespan.

How hidden heating leaks are found

Zone isolation: the loop is divided zone by zone, and the zone that won't hold pressure is the culprit. Then thermal imaging maps the tubing's heat pattern to spot the anomaly, sometimes with acoustic confirmation. Note the Utah framing: most local homes are forced-air, so hydronic expertise is genuinely specialized here — make sure whoever investigates understands closed-loop diagnostics, not just domestic plumbing.

Frequently asked questions