Unvented Hot Water Cylinders in Edinburgh

Not every property should be on a combi, and a lot of Edinburgh housing is better served by stored hot water. This is the cylinder side of the system: unvented cylinders running at mains pressure, traditional vented cylinders fed from a tank in the loft, immersion heaters, point-of-use water heaters and the cold water storage that feeds the older arrangements. If a house has two bathrooms and an ambition to use both at once, stored hot water usually answers it better than a combi trying to keep up.

Unvented cylinders are the modern default, and they are a separate discipline rather than a bigger tank. They hold hot water at mains pressure, which is what gives you a decent shower on the top floor without a pump, and they carry a set of safety devices — expansion vessel, pressure and temperature relief, tundish and discharge pipework — that have to be installed correctly and checked annually to keep working. Servicing them is not optional in the way people treat a boiler service as optional; a discharge that has been quietly weeping for two years is telling you something.

Vented systems have not gone away, especially in flats where the loft tank and cylinder cupboard are original. They are simple, cheap to repair and forgiving, but they are limited by the height of the tank above the outlet, which is why a top-floor flat can have a bath that fills fine and a shower that barely runs. Edinburgh’s water supply is soft compared with much of England, so cylinders here suffer less from scale than they would further south — but they still corrode, and a cylinder that has started to weep is replaced rather than patched. If you are converting to a combi, the redundant tank and cylinder go out as part of the boiler installation.