Central Heating Maintenance

A central heating service is a check of the whole system, not only the boiler:

• Circulating pump: We check it runs at the right speed setting, is not noisy or seized, and is not leaking.
• Motorised and zone valves: The valves that send hot water to the heating, the hot water cylinder or different zones. We check each one opens and closes fully.
• Expansion vessel: It absorbs the expansion of the water as it heats up. We check its air charge and re-pressurise it if needed.
• System pressure: On a sealed system, we check the pressure holds steady and look for the cause if it keeps dropping or rising.
• Water quality: We test the inhibitor level and check for sludge (magnetite), and clean the magnetic filter if one is fitted.
• Radiators and valves: We check for cold spots, leaks and stiff thermostatic radiator valves, and bleed air out of the system.
• Balancing: We adjust the lockshield valves so every radiator heats up evenly.
• Controls: We check the programmer, room thermostat and cylinder thermostat are switching the heating and hot water correctly.

You receive a written note of what we found and anything that needs attention.

They are different checks. A boiler service is the yearly safety and efficiency check of the boiler itself: the burner, seals, flue and combustion. A central heating service covers everything the boiler feeds. Many people book both at the same visit. If you are a landlord, the legal yearly check is a landlord gas safety certificate, which is different again.

Once a year is a sensible routine for most homes, ideally before the colder months, when a fault is most inconvenient. Book a check sooner if the pressure keeps dropping, radiators heat unevenly, the system is noisy or the heating takes longer to warm up than it used to.

The boiler may be fine while another part of the system has failed:

If the boiler itself shows a fault code or will not fire, see our boiler repair service. A diverter valve inside a combi boiler is a boiler part, so it is repaired there too. For a thermostat or programmer that has stopped working, see thermostat and control maintenance and repair. If you have no heat at all in cold weather, our emergency heating services page explains what to do now.

Where the cold spot is tells you a lot:

• Cold at the top: Trapped air. Bleeding the radiator usually fixes it, but if it keeps happening, air is getting in somewhere and the cause needs finding.
• Cold at the bottom or in the middle: Sludge settling in the radiator. One radiator can be cleaned; if several are affected, power flushing cleans the whole system.
• Radiators far from the boiler stay cool: The system is out of balance, so hot water takes the shortest route. Balancing fixes it.

A single faulty radiator, a leaking valve or a stuck thermostatic radiator valve is covered by our radiator maintenance and repair service.

The water in a heating system slowly corrodes the steel radiators, producing black sludge that blocks pipes, cold-spots radiators and wears out pumps and boilers. BS 7593 is the British Standard for treating heating system water. In practice, that means keeping a correct dose of inhibitor in the system, testing it, and fitting a magnetic filter to catch debris before it reaches the boiler. Badly contaminated water is cleaned out first.