General questions relating to mechanical issues.

Boiler pressure drops are typically caused by a leak in the system or a faulty pressure relief valve. If you find yourself constantly topping up the system, it's time to investigate. You can visually check exposed pipework and radiator valves for drips. Before calling out one of our Home Heating Heroes, use your DIY Home Heating Test Kit to rule out internal system degradation, as poor water quality can accelerate component failure.

Cold spots at the bottom of a radiator usually mean one thing: sludge build-up. Over time, rust and debris settle at the bottom of your heating system. Bleeding the radiator only helps if the cold spot is at the top (which indicates trapped air). For total peace of mind, the test kit allows you to sample the system water and see exactly what's circulating. You can then share your personalized dashboard with a professional to arrange a system clean if needed.

That kettling sound is often caused by limescale or sludge building up on the heat exchanger, restricting water flow and causing it to boil locally. Boiler manufacturers and BS Standards expect your system water to be clean to remain warranty compliant. If you hire a professional for a flush, remember that the ability to re-test turns the Home Heating Test Kits into a 'Certificate of Completion.' If Test ONE fails, and the job has been done correctly, Test TWO should pass. If not, the contractor should be asked to do the job again and tested again.

If your taps are hot but the radiators are ice cold, the most common culprit is a stuck diverter valve in a combi boiler. This valve directs the heat either to your domestic hot water or your radiators. Occasionally, it's a communication error with your thermostat. Double-check your settings first; if calibrated correctly, an approved partner will need to unstick or replace the valve.

During cold snaps, the external condensate pipe can freeze, causing the boiler to lock out and display a fault code. You can often fix this yourself without calling out a professional. Simply pour warm (never boiling) water over the frozen section of the pipe outside, or wrap a hot water bottle around it until the ice clears and you can safely reset the boiler.

Air naturally gets trapped in heating systems over time, causing radiators to feel cold at the top and warm at the bottom. You should bleed your radiators at least once a year, ideally in early autumn before turning the heating on daily. If you find yourself needing to bleed them every few weeks, it points to a wider issue, such as a microscopic leak letting air in, or hydrogen gas building up as a byproduct of internal rust and corrosion.

If a single radiator is failing to heat up, the most likely culprit is a stuck pin inside the Thermostatic Radiator Valve (TRV). By removing the plastic TRV head, you can gently tap the exposed metal pin until it springs back up. If the valve is functioning normally, the heating system might be unbalanced. This means hot water is taking the path of least resistance and skipping that specific radiator, requiring the lockshield valves to be adjusted to distribute heat evenly across the property.

Inhibitor is a vital chemical treatment that prevents internal rust and stops sludge from forming inside your pipes, radiators, and boiler heat exchanger. Operating without sufficient inhibitor will degrade your system rapidly and almost always voids the manufacturer's warranty. The only accurate way to verify adequate inhibitor levels is by testing the system water. Regular sampling ensures your system stays clean, compliant with BS Standards, and protected against premature component failure. The perfect job for the Dr Radiator Home Heating Test Kit.

If the boiler burner is igniting but no heat is reaching the radiators, the central heating pump has likely failed or seized. The pump is responsible for circulating the hot water around the property. Sometimes a gentle tap can free a stuck pump, but if it has burnt out—often due to working too hard against thick sludge in the water—it will require a professional replacement.

This could just be trapped air in the system. The radiators may simply need bleeding with a key. (Note: Sludge buildup causes the exact opposite—cold at the bottom, hot at the top).

Heavy curtains draped over a TRV, or furniture blocking it. The trapped heat tricks the TRV's sensor into thinking the whole room is up to temperature.

If a central heating system requires topping up every few days or weeks it's likely due to a physical leak on the pipework network or a failed expansion vessel.