Why Are My Radiators Getting Hot When the Heating is Off?

Balancing Radiators: How to Guide
Balancing Radiators: How to Guide

At one time or another everyone has had the misfortune of having to temporarily cope without heating due to a malfunctioning boiler. There is also the flipside whereby you cannot turn down the heat, which is just as uncomfortable, especially during the warmer months of the year.

The problem of radiators getting hot even when your heating is switched off occurs more commonly than you might imagine. But what causes this to happen? We provide the two main reasons for this phenomenon in the following article.

Problems With Your Diverter Valve 

Diverter valves open and close to allow or cut off hot water that flows through your heating system and radiators. When hot waters need to be sent from the boiler to radiators instead of the taps, for instance, the tap diverter valve will close.

This is a similar concept to bathtubs that have a showerhead in addition to the normal taps. A diverter valve will direct the flow of water to either the showerhead or the tap, depending on your selection. On the other hand, diverters will go to a ‘mid’ position if water flow is needed for both your hot water system and radiators at the same time.

Due to the fact that these valves keep opening and closing as required throughout the day, they can get stuck or become damaged. When this happens, hot water may continue to flow through to your radiators – even when your heating is switched off.

If this is the case, get in touch with a qualified engineer to come and take a look at the problem. The Gas Safe Register is a great place to find a local tradesman in your area. They will carry out some tests to check if the diverter valve is the issue or whether there’s another underlying problem. If the valve were at fault, it would either need to be cleaned or replaced. In circumstances where it needs to be replaced you’re advised to check whether your boiler is still under warranty. If so, you will likely be able to get a new one at no extra cost (excluding the labour cost, unless a manufacturer-approved specialist is used).

A Broken Check Valve 

Older boilers keep water hot at all times. The hot water then travels through your radiators by natural convection. When you need to heat up your home, the water is pumped from the boiler through to your radiators. Once your home reaches the desired temperature, the heat turns off which causes the pump to stop running.

A check valve is used to stop the natural convection from warming up your home when your heating is switched off. If the check valve is broken or blocked, heat will rise through your system causing your radiators to stay hot.

Once again, contact a qualified professional to come and check what the problem is. After running some diagnostics they’ll be able to fix the issue safely and correctly. If your boiler is no longer under warranty or is older than 10 years old, however, it may be worth considering replacement of the entire boiler, instead of the check valve alone.


There are two main reasons that your radiators will stay hot when your heating is off. It normally comes down to a problem with either your diverter valve or your check valve. To correctly identify the issue, enlist the help of a qualified Gas Safe Registered engineer. They’ll run some tests and establish whether it is indeed a check valve or diverter valve at fault – or a different underlying issue altogether. Thereafter, they’ll advise you on the findings and carry out the repair work to restore your central heating system back to normal.