Unvented cylinder servicing in Macclesfield
In short
An unvented cylinder needs an annual service by a G3-qualified engineer: expansion vessel charge, relief valve operation, temperature controls and discharge arrangement. It is a pressure vessel with safety devices that only prove themselves when tested, and most warranties require the service to stay valid.
Also called: cylinder service · Megaflo service · unvented annual service · expansion vessel check
The service is short but specific. The expansion vessel's air charge is checked and recharged, because a vessel that has lost its charge means every heat-up pushes water out through the expansion relief valve — which shows up as water discharging outside and, eventually, as valves that no longer seal. The temperature and pressure relief valve and the expansion relief valve are both operated and checked for reseating. The thermostat and the thermal cut-out are verified. The discharge pipework is inspected. The immersion heater and its own thermal cut-out are checked.
The most common finding is a discharged expansion vessel. It is a wear item — the air charge migrates through the diaphragm over years — and the symptom is water at the tundish or the outside discharge point every time the cylinder heats. People often assume a failed valve; it is usually the vessel.
The second most common finding is a discharge arrangement that was never right. The tundish must be visible and sited within the required distance of the valve, the pipe must fall continuously, be of adequate size for its length and bends, and terminate somewhere safe where a discharge of near-boiling water cannot scald anyone. A discharge into a hidden void is a genuine hazard.
Stored water temperature is part of the check. It should sit at 60°C: hot enough to prevent legionella bacteria establishing in the stored water, with blending valves used where necessary to limit the temperature reaching baths and basins so nobody is scalded. Turning a cylinder down to save energy below that threshold is a false economy with a real risk attached.
For landlords, the cylinder service sits alongside the gas safety check as part of sensible property maintenance, and the water temperature aspect connects directly to legionella risk assessment duties.
What the job covers
- Expansion vessel charge test and recharge
- Expansion relief and temperature/pressure relief valve testing
- Thermostat and thermal cut-out verification
- Discharge pipework and tundish inspection
- Immersion heater check and stored temperature confirmation
- Service record for warranty and landlord purposes
What it costs
We don't publish a price for this yet, because a number pulled out of the air is worse than no number at all — your plumber has to honour it. You'll get a firm price for your actual job when they ring you back, before any work starts. The quote itself is free and there's no obligation either way.
Common questions
Why is water dripping from the pipe outside when the cylinder heats?
Almost always a lost expansion vessel charge — the expanding water has nowhere to go and exits through the relief valve. Recharging or replacing the vessel fixes it, and it should be done promptly because repeated discharge damages the valve seat.
What temperature should the cylinder be set to?
60°C for stored water, which prevents legionella establishing. Where scalding is a concern, the answer is a blending valve limiting the temperature at the tap, not a lower cylinder setting.
Need this doing in Macclesfield?
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