Why radiator valves need a little attention

Radiator valves are small components but they do a big job. Thermostatic radiator valves (TRVs) and manual valves control how much hot water flows through each radiator. When they work well, every room reaches its set temperature without wasting energy. When they stick, leak or fall out of balance, your heating can become uneven, noisy or more expensive to run. Most valve care is simple and fits into your normal heating routine.

Thermostatic and manual valves: what you are dealing with

TRVs have a wax or liquid-filled sensor. They sense room air temperature and open or close the valve accordingly. Manual valves, often called wheelhead valves, are turned by hand and stay where you leave them. Lockshield valves sit at the other end of the radiator and are usually covered by a plastic cap; they are used to balance the system and should not be adjusted casually.

• TRV: numbered dial, responds to room temperature, best set to a comfortable temperature rather than turned up to warm a room faster.
• Manual wheelhead: simple on/off or gradual control, often found on older systems or where a room needs a fixed flow.
• Lockshield: set during balancing, not a room temperature control. Only adjust if you are following a proper balancing procedure.

Keep thermostatic valves moving

The most common problem with a TRV is a stuck pin. Over summer, the pin can seize in the closed position, so the radiator stays cold even when the heating comes on. Once a month during heating season, and at least once in summer, turn the TRV from its normal setting to maximum and back to minimum. If the head is removable, unscrew the collar and check the pin. With the heating off, press the pin gently with a flat tool or pliers; it should spring back. If it does not, a few drops of silicone lubricant on the pin, not oil, may help. Never force it. If the pin remains stuck, fit a new TRV head or ask a plumber to replace the valve body.

Check the head is secure. A loose TRV head can read the wrong air temperature, causing overheating or underheating. Tighten the collar hand-tight only, and never use a spanner on plastic parts.

Check for leaks and weeping joints

A small weep from a valve nut can look harmless, but it can corrode the radiator, stain walls and eventually drop boiler pressure. Run a dry tissue around the valve body, the spindle and the pipe connections before and after the heating has been on. If the tissue shows water, note exactly where. For a slight weep at a compression nut, a quarter turn with the correct spanner may stop it, but do not over-tighten. Over-tightening can crush the olive and make the leak worse. If water is coming from the spindle of a manual valve, the gland nut may need a small nip. If the valve body itself is leaking, or if the leak continues, isolate the radiator and call a plumber. Keep towels away from boiler controls and never open a boiler casing yourself.

Balance, bleed and seasonal habits

Valves work best in a balanced system. If upstairs radiators heat quickly and downstairs ones stay lukewarm, the lockshield valves may need adjusting. Balancing is a step-by-step process: with the heating on, start with the radiator that heats fastest, and close its lockshield slightly while checking temperatures at the flow and return pipes. The aim is a small temperature drop across each radiator, typically around 10 to 12 degrees Celsius. Bleeding radiators also helps. Air trapped at the top of a radiator stops it heating fully. Use a radiator key, open the bleed valve until water trickles out, then close it. Top up boiler pressure afterwards; most sealed systems want 1 to 1.5 bar cold.

Once a year, before winter, walk around the house and turn every TRV and manual valve through its full range. This simple habit stops seals drying out and pins seizing. Clean any system filter annually and keep inhibitor levels correct; sludge and corrosion can clog valve bodies and make them stiff.

Gas safety and when to call a professional

Radiator valves are usually safe to maintain yourself, but gas appliances are not. Any work on a gas boiler, gas fire or gas pipework must be done by a registered gas engineer. Book an annual boiler service and keep the record. Fit an audible carbon monoxide alarm in the same room as any gas appliance, and test it monthly. Never block ventilation bricks or air vents, and keep flues and outside terminals clear of leaves, nests and clutter.

If you smell gas, do not touch electrical switches, use a phone indoors or light a flame. Open doors and windows, turn off the gas at the meter if it is safe to do so, and leave the property. Call the gas emergency service from outside. If you suspect carbon monoxide, get fresh air and seek medical advice. For valve problems that involve draining the system, soldering pipework or opening a sealed boiler, use a qualified plumber or heating engineer. A little routine care keeps your heating efficient, your rooms comfortable and your home safer.