Identifying an unvented cylinder

The cylinder is usually made from copper covered in a fibreglass lagging or even foam insulating material. At the top of the cylinder is a single pipe that emerges and then immediately turn sideways so that it is more or less horizontal to the tank but actually rising very gently. Harringay Plumbers service this equipment. The pipe then splits into a tee, with one going up and the other going down. If you follow the pipe going up you’ll eventually arrive at a cold-water storage tank, and this vent pipe will terminate over the top of it. It will be arranged so that if water ever fills the pipe it will just pour out of it and into the cold-water storage tank. If you managed to find this vent pipe then you have a standard ‘vented’ hot-water cylinder. If you didn’t, the odds are you have an unvented cylinder, which will have the following general characteristics:

a). You usually cant see the insulation, i.e. it has an outer skin that is usually made from thin steel. A Harringay Plumber can tell the difference.
b). It’s either has a flat top or there’s an expansion vessel close by.
c). It has a series of valves attached to it, or to the expansion vessel.
d). It has a tundish close by, or a gap in the pipe so that you can see the water running through it. Why should you want to see the water? Well, if all is well there should never be water in this type. However, if any of the safety devices kick in, you’ll see water either dripping or pouring through it. When this happens something’s gone wrong and you need to call a plumber with the relevant G3 qualifications to check the cylinder.


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