Vented Copper Cylinders and Gravity Hot Water
A vented cylinder is the older copper unit fed from a cold tank in the loft, open to the atmosphere through a vent pipe.
A vented cylinder is the older copper unit fed from a cold tank in the loft, open to the atmosphere through a vent pipe. It is a forgiving arrangement with genuinely low running risks, and its weakness is pressure rather than safety.
How the pressure is created
Only by height. A metre of height gives roughly a tenth of a bar, which is why a loft tank two metres above a bath gives such a gentle flow.
Where heat is lost
Uninsulated pipework and thin old jackets. A modern factory-foamed cylinder holds heat far better than a lagged 1970s copper one.
Realistic upgrade paths
Keep and improve it, add a shower pump for the bathroom only, or convert to unvented if the mains supply supports it.
Questions we get asked
Can I fit a power shower to a vented cylinder?
Usually yes, provided the pump can draw from both the cylinder and the cold tank correctly with a proper flange or surrey fitting.
Is an immersion heater a sensible backup?
It is, and on a vented cylinder it is a straightforward one. It will heat water if the boiler fails.
Should I replace a working copper cylinder?
Not for its own sake. We would only recommend it if the coil is scaled, the insulation is poor or you are changing the system anyway.