Why your unvented cylinder needs an annual service

An unvented cylinder gives you powerful hot water to every tap without a loft tank, which is why so many homes choose them. The trade-off is that they are pressurised vessels with safety components, and those need checking once a year by a qualified engineer.

How an unvented cylinder works

Rather than relying on gravity from a tank in the loft, an unvented cylinder is fed directly from the mains and stores hot water under pressure. That is what gives you the strong flow at the shower and taps.

Why the annual service matters

Because the cylinder holds hot water under pressure, it relies on safety devices such as an expansion vessel and pressure-relief valves. These are checked and, where needed, recharged or replaced during a service, keeping the system safe and within its warranty.

• Expansion vessel charge and condition
• Pressure and temperature relief valves
• The discharge pipework
• General condition and controls

Signs your cylinder needs attention

Weak or inconsistent pressure, slow recovery after a shower, rumbling noises, or water dripping from the outside discharge pipe are all worth a call. Caught early, most are a straightforward fix.

Key takeaways

• Unvented cylinders store hot water under mains pressure
• Their safety parts must be checked every year
• An annual service also protects the manufacturer warranty