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Do you Need to Balance Radiators on a Combi Boiler System?

Combi boilers offer a great way to efficiently heat your home and give you hot water on demand. However, sometimes your radiators may heat up unevenly. Thankfully, rebalancing your radiators is one way you can prevent this from happening.

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Combi boilers offer a great way to efficiently heat your home and give you hot water on demand. However, sometimes your radiators may heat up unevenly and cause some rooms to take longer to heat up than others. 


Thankfully, rebalancing your radiators is one way you can prevent this from happening. In this guide, we’ll explain everything you need to know about balancing your radiators.


It is so important to notes however, that both these things are better done by a plumber or heating engineer.


How do you know if radiators need balancing?

Balancing your radiator means adjusting the valves to level the water flow, ensuring each radiator in your home heats up at the same time. 


There are a number of ways you can identify if your radiator needs balancing, including:


  • Cold radiators
  • Uneven temperatures across individual radiators
  • Different temperatures of radiators throughout your home
  • Radiators taking an excessively long time to heat up


If you experience any of the above, it’s likely your central heating needs to be balanced. 

Do you need to balance radiators with a combi boiler system?

You will only need to balance radiators with a combi boiler system if you feel like you are experiencing any of the problems we have previously discussed. If some of the radiators in your home take much longer to heat up than others, then you will probably benefit from balancing them. 

Balancing your radiators can actually increase the efficiency of your heating system by as much as 15%.

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How do you balance radiators on a combi boiler system?

It is in your best and safest interest to involve a plumber or heating engineer when bleeding radiators, but we’ve listed the steps below in case you want to know what it includes.


Before you start balancing your radiators, there are a few thing you’ll need, including:


  • Radiator keys
  • Lockshield valve key or an adjustable spanner
  • Thermometer 
  • Screwdriver 


Now you can follow the steps below:

  • Turn off the central heating – Before you start, turn off your central heating and give it time to cool down.

  • Bleed the radiators – Once the radiators have all cooled down, you will need to bleed them. Bleeding radiators helps to remove any trapped air in the heating system.

  • Turn the heating back on – Now you will need to turn the heating back on by turning up the thermostat. You should keep an eye on the radiators, taking note on which ones heat up the slowest. You may need some helpers for this!

  • Turn the heating off – Once you’ve ordered the radiators from fastest to slowest in heating up, you can turn the heating off again. Give it time to cool down before you carry on with the next step.

  • Turn the heating on again – Now you can go through your list of the radiators, starting with the one which heated up the quickest. Turn the lockshield valves clockwise until closed and then open it again by one quarter of a turn. Do this for each radiator, opening radiators that are further away from the boiler a small amount more than the closer ones. 

Once you’ve finished all of these steps, your radiators should be balanced and your boiler will deliver water in a more even fashion throughout. 

How to change a radiator valve with a combi boiler


To change a radiator valve, you will need:


  • Your new valve
  • A wrench
  • A spanner
  • Some wire wool
  • Old towels or cloths
Radiator image

Use the following steps below if you have a combi boiler system and you need to change the radiator valve:

  • Turn off the heating and water supply – The first thing you should do is make sure your heating and water supply is turned off. This will help to prevent any unexpected messes. Make sure your thermostat is set to 0 so there is no chance of your heating kicking back in.

  • Put down towels – Lay down some old towels or rags to protect your flooring. You should put them underneath your radiator and the surrounding pipes.

    At this point you should also prepare your valves. You should take the nuts and connectors off the new valves so that it’s ready to be fixed to the radiator.

  • Drain your system – Before you fit your new valve, you will need your radiators to be emptied of water. First, you should find your drain-off valve. This is likely to be underneath one of your downstairs radiators.

    You will also need to bleed all the radiators in your house.

  • Remove the old radiator valve – Once the water has been drained out of your heating system, you should take off your old valve.

    Hold the body of the valve with a wrench and use the spanner to undo the top and bottom nut of the valve by turning them anti-clockwise. As it loosens, take the valve off the radiator and use the wire wool to clean up the pipes.

  • Fit the new valve – Now all you need to do is put the new valve where your old one was. Make sure it’s aligned with the water pipe and the radiator tail.

As before, hold onto the body of the valve with your wrench while tightening the nuts with your spanner. Be sure not to tighten the valve connections too fast or too tight as this can damage the thread.

  • Turn the water back on and bleed the radiators – Once your new valve is attached, you should turn the water back on. Make sure all of the radiator bleed valves are closed. Make sure your lockshield thermostatic valves are open so water can flow into the radiator you were working on.

    You’ll need to re-pressurise your system and make sure everything is working properly. You should bleed the radiators one more time to let out any air that became trapped inside as it refilled. 


Do I need a plumber to balance radiators?

While the process of balancing radiators can be relatively simple, it can be daunting to do if you’ve never done it before. This is where a professional heating and plumbing expert can help. 

Our team at Lacey Plumbing & Heating have years of experience helping domestic and commercial customers to balance their heating systems. If you think your heating system needs to be balanced and don’t feel comfortable doing it by yourself, get in touch with our team today to see how we can help.

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