Hot Water CylinderInstallation Across EssexVented and Unvented, Certified

An unvented cylinder is a sealed vessel fed at mains pressure. Because there is no atmospheric vent, expansion is absorbed by an expansion vessel or internal air gap, and the vessel is protected by a pressure relief valve and a temperature and pressure relief valve discharging through a tundish to a safe termination. The payoff is mains pressure at every outlet and no tanks in the loft.

A vented cylinder is open to atmosphere via a cold water storage tank, usually in the loft. Pressure at the taps depends on the height of that tank above the outlet, which is why top-floor showers on vented systems are often weak without a pump. Vented systems remain a sound choice where mains pressure is genuinely poor, and they are simpler and cheaper to install.

Where the incoming main is weak, an unvented cylinder will not create pressure that does not exist. In those cases the options are a vented arrangement, a pump, or an accumulator, and we assess that with actual flow and pressure figures at survey rather than assuming.

Cylinder capacity should be based on peak demand, how much hot water your household needs in its busiest hour, rather than a general rule. Undersize it and you run out mid-shower; oversize it substantially and you pay to keep water hot that nobody uses.

Recovery time depends on the coil surface area and the boiler output feeding it. A high-recovery coil on a system boiler reheats a cylinder considerably faster than an older low-surface coil, which matters far more in practice for a busy household than a slightly larger volume.

Cylinders can be heated by the boiler coil, by an immersion heater as backup, or by additional coils for solar thermal or a heat pump where those are present. Immersion heaters are worth specifying as a fallback: they keep hot water available if the boiler fails.

Unvented cylinders should be serviced annually. The service checks the expansion vessel charge, tests the relief valves, checks the tundish and discharge arrangement, inspects the immersion and thermostats, and confirms operating pressures. Manufacturers make this a condition of warranty.

The most common fault we find is a discharged or waterlogged expansion vessel, which shows up as pressure surges and a dripping tundish. Left alone, the relief valve is repeatedly asked to relieve pressure it was never intended to handle routinely, and it eventually passes permanently.

Scale is the other factor in harder water areas: it reduces coil efficiency and can affect immersion elements over time. Where scale is an issue, we will discuss treatment options as part of the specification rather than after the cylinder is in.

We install and replace cylinders in Braintree, Colchester, Kelvedon, Tiptree, Feering, Halstead, Sudbury, Sible Hedingham, Coggeshall and the surrounding villages. A very common job in this area is converting a vented, tank-fed system in an older house into an unvented arrangement when a second bathroom or en-suite is added.

Cylinder work usually pairs with boiler and heating work, since the boiler is the heat source and its output determines recovery. Where both are due, doing them together avoids paying twice for the same access and the same drain-down.