The photograph is the base of a hot water cylinder on one of our jobs, and shows the parts this post is about.
Why is my hot water cylinder leaking?
Usually the water is coming off the pipework at the base of the cylinder: a joint, a valve or a drain cock. On a cylinder fed straight off the mains, water at the tundish means a safety valve is letting go. The cylinder itself wearing through is rarer. London City Plumbers finds which it is first.
The cylinder is in bare yellow foam insulation with no outer casing. On the left are copper pipes and a brass valve under a green cap. In the middle, a braided flexible hose loops around a black circular cover. On the right, a brass elbow goes into the cylinder through a cut-out in the foam, with white pipe clips below it and rust staining on the foam round the fitting.
The rust marks
The rust in the photograph is the kind of mark water leaves when it has run down the outside of a cylinder.
A mark like that shows where water has been, not where it started, and the place to look first is above it.
Most water round a cylinder is not the cylinder itself.
The usual places
The first job with a hot water cylinder leaking is finding where the water comes off it, and the list of places is short. One is a joint or a valve on the pipework at the base, where everything goes in and out. Another is the boss, the opening where a pipe or the immersion heater goes into the cylinder, and its seal can weep. A drain cock at the very bottom can be knocked, or start to weep. On a cylinder fed straight off the mains, water at the tundish, the open gap in the pipe under its safety valves, means a safety valve is letting water go. That is the valve doing its job because something else is wrong, and that work is for someone qualified in unvented systems. Rarer than any of these is the cylinder itself wearing through, often low down on an older copper one. That cannot be patched, and it means a new cylinder.
A dripping tundish is the warning, not the fault.
The stopcock
If it is more than a drip, turn the water off at the stopcock, clockwise until it stops, put a bowl or towels under it, and ring us.
We find where the water is coming off before anything is changed. A joint, a valve or a drain cock is a plumbing repair, and the cylinder stays where it is.
Other cylinder jobs
Our emergency plumber page covers leaks, even one nobody can trace, and finding the stopcock. We have written up another job on a cylinder, and a two port valve fitted beside one.
Ring 07546 185778 and say where the water is: on a pipe, at a valve, at the very bottom, or through the tundish.
