Balancing the radiators may be necessary if you find that some are too hot or too cold. By adjusting each radiator’s lockshield, you can control how much hot water flows through them so they all heat up evenly.
- Bleed the radiators.
- Fully open all lockshields and thermostatic radiator valves (TRVs) and turn the central heating on.
- After 20 minutes, feel each radiator. If one is distinctly hotter than the others, close the lockshield by a quarter turn and leave it for 20 minutes.
- Check all radiators again. Once again, if it’s distinctly hotter than the others, close the lockshield by a quarter turn and leave it for 20 minutes.
- Repeat the process until all radiators feel the same temperature.
Why do you have to balance the radiators?
There are two main reasons. The first one is because hot water rises, and so the upstairs radiators naturally tend to get hotter than the ones downstairs. The other reason is that the water always wants to take the path of least resistance back to the pump. This is usually the shortest route in the system. In an unbalanced system, this means that the radiator closest to the pump is likely to be the hottest. If the pump is inside the boiler, the hottest radiator is probably going to be the one closest to the boiler.
Balancing the radiators has several advantages. Firstly, your boiler won’t need to work overtime to compensate for radiators which aren’t heating up certain rooms properly. It won’t need to run for as long and it may also run at a lower overall temperature, meaning lower fuel bills.
In order to compensate for an unbalanced system, people sometimes increase the pump speed. This doesn’t solve the problem, and simply creates more wear and tear on the pump. Plus, keeping the pump speed low reduces the risk of water hammer.
Balancing radiators explained
This can be done in two different ways: either by feeling each radiator with your hand or with a radiator balancing kit or thermometer.
Balancing radiators with a thermometer or balancing kit
Bleed the radiators. Turn the central heating off and allow the system to cool down.
Open all lockshields and thermostatic radiator valves (TRVs). As mentioned, the lockshield is covered by a small plastic cap which must be removed. You’ll need an adjustable spanner to operate the valve itself.
Turn your central heating back on and write down the order in which your radiators heat up. Once you’ve done that, turn your heating off again and let all the radiators cool down.
Starting with the first radiator on your list, turn the heating back on and close the lockshield valve. Then, open it a quarter turn.
Using a thermometer or your balancing kit, check the temperature of the pipe connected to the TRV and make a note of it. Next, check the temperature of the pipe connected to the lockshield and make a note of it. After emitting its heat, water exits the radiator via the lockshield, so this reading should be the cooler one.
You need to open the lockshield enough so that the difference between the two temperatures is 12°C. After each adjustment to the lockshield, let the temperature stabilise for 2-5 minutes before adjusting it again. This will ensure that your readings are accurate.
If your lockshield reading is higher than the TRV reading, this means that the lockshield has been fitted on the flow side of the radiator and not on the return. This is not good plumbing practice, but as long as you are adjusting the lockshield and not the TRV in order to set the 12°C discrepancy, you should be able to balance the radiator normally.
Do the same for the rest of your radiators in the order that they heat up. Generally speaking, the further the radiator is from the boiler or pump, the more open the lockshield will need to be. You may find that on some radiators, the lockshield may need to be almost or even completely open.
Well done – you have balanced the radiators. If you have one radiator not working properly and balancing the system doesn’t make any difference, check out our page on this topic: One radiator not working: 5 common causes & how to fix.