BoilerTroubleshooting2026-01-18
Why Your Boiler Keeps Losing Pressure
Recurring pressure loss usually means a leak, a failed relief valve, or a waterlogged expansion vessel.
If you're constantly topping up your boiler's pressure, you're treating a symptom. Finding the real cause stops the cycle.
The three main causes
A system leak (visible or hidden), a leaking pressure-relief valve discharging outside, or a waterlogged expansion vessel that can't absorb expansion are the usual reasons pressure keeps dropping.
Why it matters
Repeated re-pressurizing adds fresh, oxygenated water that accelerates internal corrosion and sludge. A proper diagnosis and repair protects the boiler.
Key takeaways
- Look for damp patches and PRV discharge outside
- Repeated top-ups often mean a hidden leak
- Expansion-vessel recharge or replacement may be needed
- Avoid constant re-pressurizing — it corrodes the system
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