Project Overview
| Location | Chestnut Road, Ashford, Middlesex (TW15) |
|---|---|
| Call-out | Emergency out-of-hours safety visit — leaking cylinder |
| System | Potterton Promax System 24 HE A with hot water cylinder in the garage |
| Fault found | Failed cylinder expansion vessel; blown electrical fuse from water ingress |
| Work completed | Cylinder isolated, fuse replaced, controls dried, system left off pending a quotation |
The Challenge
We were originally asked to quote for a leaking cylinder in Ashford, then called out of hours the same evening as an emergency plumber. On arrival the garage floor was flooded. The expansion vessel on the hot water cylinder had rusted through at the base and was still losing water — a plumbing leak that had already reached the electrics serving the boiler.
The job that night was not a full cylinder replacement. It was a make-safe: stop the leak as far as possible, restore power only if it was safe to do so, and leave the system in a condition the household could live with until a proper repair could be quoted.
The Solution: Isolate the Cylinder and Make the Electrics Safe
The Zilmet expansion vessel on the cylinder had failed completely. We isolated the cylinder, left a container under the ruptured base to catch the last drips, and stopped any further work on the stored-hot-water side pending instruction.
Because the leak had reached the garage electrics, the fuse supplying the Potterton Promax and the heating controls had blown. The wiring centre and programmer were dried out and the fuse was replaced so power could be restored safely. System pressure on the Promax was then checked and confirmed in the green zone. The heating was left switched off as a precaution — water and live controls in the same garage is not something to leave running overnight.
Why the Expansion Vessel Failed
An expansion vessel on a hot water cylinder absorbs the extra volume as water heats up. When the internal bladder perishes or the steel shell corrodes through, that pressure has nowhere to go except out of the vessel — onto the floor, and in this garage onto the fuse board.
- Eighteen years in service: The data plate is a Zilmet 18 litre vessel, built in September 2008. That is a long life for a wet, uninspected component in a garage.
- Failure at the base: The shell had opened at the bottom connection, which is why water was still dripping after the cylinder was isolated.
- Water into electrics: The same leak took out the fuse to the boiler and controls. Drying the wiring centre and replacing that fuse was what made it safe to restore power.
- Garage still flooded: The full extent of floor damage could not be confirmed on the night — the garage had not yet been cleared for a complete inspection.
The Repair Process
- Arrival: Out-of-hours safety visit in Ashford after a leaking-cylinder enquiry. The garage floor was flooded from the failed vessel.
- Make-safe: The cylinder was isolated and a container left under the ruptured expansion vessel to catch residual drips. No further cylinder work was carried out that night.
- Electrics: The blown fuse to the Potterton Promax and controls was replaced. The wiring centre and programmer were dried, power was restored, and boiler pressure was confirmed in the normal range.
- Left safe: The system was switched off as a precaution. A quotation would follow for replacing the vessel — and, given the age of the cylinder, for replacing the cylinder itself.
The Results
The leak was contained the same evening, the garage electrics were made safe, and the Potterton Promax had power again without being left running in a wet cupboard. The household had a clear next step rather than an open-ended emergency: replace the failed expansion vessel and safety valves, check anything the flood had reached, and decide whether the ageing cylinder is worth repairing.
Recommended Follow-Up
This visit was a make-safe, not the finished repair. The work that still needs booking:
- Expansion vessel and safety valves: Fit a new vessel and the associated safety valves. The 2008 Zilmet unit is finished.
- Water-damaged controls: Any zone valves or programmers that took on water in the garage should be replaced rather than left to fail on a later call-out.
- Cylinder repair vs replacement: The cylinder is of an age where replacement is often the better spend. A quotation should cover both a vessel-only repair and a new cylinder so the customer can choose.
- Boiler check: Once the garage is dry, a full boiler repair inspection and boiler service of the Potterton Promax will confirm nothing else was affected by the flood.
