Every street has a household on first-name terms with their filling loop: pressure drops, gets topped up, drops again, and the ritual quietly becomes normal. It is not normal. A sealed system holds its pressure, and one that keeps losing it is reporting a fault every single week.
Derek Stuart Heating & Gas repairs boilers across Byker, and recurring pressure loss is among the most common calls, and the most commonly ignored. This is what the habit is actually telling you.
Where the water goes: four escape routes
Water leaves a sealed system four ways. A weep on the circuit: a radiator valve gland, a compression joint, a pipe under a floor, sometimes showing as nothing more than a salt-crust or a stain. The pressure relief valve passing: letting water dribble to its outside discharge pipe, often after an expansion fault. The expansion vessel failed: causing pressure swings that force water out through the relief valve. Or, most seriously, a fault inside the boiler's own heat exchanger.
Each has its own tells, which is why describing the pattern matters: how often you top up, whether pressure spikes when hot, whether the outside discharge pipe drips, whether any radiator valve leaves its signature.
- Circuit weep: stains, crusts, damp patches under floors.
- Relief valve passing: the outside pipe that drips.
- Expansion vessel flat: pressure seesaws hot to cold.
- Exchanger fault: the diagnosis nobody wants but must rule out.
What the habit costs
Every top-up pours fresh, oxygenated water into the system, and fresh water feeds internal corrosion: the weekly ritual quietly manufactures sludge, dilutes inhibitor toward uselessness, and ages radiators and exchanger alike. The leak is usually cheap; the habit is expensive.
There is also the lockout roulette: a system drifting low locks the boiler out on the coldest morning of the year by preference. Pressure faults present as annoyances and graduate into breakdowns on their own schedule.
- Fresh water feeds corrosion and dilutes inhibitor.
- Sludge formation accelerates with every top-up.
- Low-pressure lockouts choose cold mornings.
How the diagnosis visit runs
The engineer's sequence is methodical: system pressurised and observed, expansion vessel charge tested, relief valve and its discharge checked for passing, visible circuit walked with a torch, and the boiler's internals inspected. Where nothing shows, thermal imaging or moisture readings hunt the underfloor weep that stains no ceiling.
Derek Stuart Heating & Gas asks for the household's log first, how often, how much, any patterns, because a week of observations narrows an hour of hunting. Bring the answers and the visit gets shorter.
The fix, and closing the loop
The repairs themselves are usually modest: a valve gland packed or replaced, a joint remade, an expansion vessel recharged or swapped, a relief valve renewed. The exchanger case is the serious one, and an honest engineer prices repair against replacement plainly when it appears.
Closing the loop matters as much as the fix: system pressure restored, inhibitor brought back to strength after all that dilution, and a fortnight's glance at the gauge to confirm the habit is genuinely over.
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Questions customers ask
How often should a sealed system need topping up?
Rarely: once or twice a year is within reason. Weekly or monthly topping up means water is escaping somewhere, and the escape route wants finding before winter finds it first.
Why does my boiler pressure rise when the heating runs?
Some rise is normal as water expands. Dramatic swings that end with the relief valve dripping outside usually mean the expansion vessel has lost its charge, which is a standard, fixable fault.
Can I just keep topping up instead of repairing?
You can, and the system will quietly bill you for it in corrosion, sludge and an eventual cold-morning lockout. The leak is almost always the cheaper party in that arrangement.
A pressure gauge that needs weekly attention is a fault with a routine, not a routine without a fault. Find the escape route, fix it once, and retire the filling loop to its proper ceremonial role.
Derek Stuart Heating & Gas handles boiler repairs in Byker with the diagnosis done properly first. The contact page takes your pattern.
