How to Balance Radiators: A Quick Guide

This guide is part of our new blog, you can see all of our entries here. Radiator balancing is the process of adjusting the valves on the radiators, so the entire system warms up quickly and efficiently.

If you find that some of your radiators are taking a long time to warm up or have cold spots, this guide is for you.

The good news is that this task is simple and anyone with basic DIY skills can do it easily.

Unfortunately, there is some bad news.

If you want to balance the radiators properly, you’ll need a digital thermometer and chances are you don’t have one. Don’t worry though; there’s a workaround for this, so keep reading.

Tools You’ll Need

To complete this task you’ll need:

Familiarize Yourself With The Different Valves

Most radiators in the UK will have three valves:

  1. A bleed valve for releasing trapped air.
  2. A TRV or wheel valve for adjusting the temperature of each rad.
  3. A Lockshield valve which usually has a plastic cap screwed on top of it.

The photos below should help you to identify each valve:

Bleed valve on rad

Bleed valve located on of this radiator (click to enlarge)

TRV wheel valve

TRV wheel valve

Radiator Lockshield cap

Lockshield cap and screw

Step 1

The first step is to bleed all of the radiators in the house. This task is quick and simple and will remove any air from the radiators and pipes; this alone can solve many common issues such as cold spots in radiators.

If you’re not sure how to bleed radiators, check out this guide.

Bleed key

Radiator bleed valve key (click to enlarge)

Step 2

The second step is to switch off the heating and open the two valves on either side of the radiator. One will look like a wheel and may have numbers on it. The other may have a screw and cap that you need to remove, revealing a small spindle that you can twist with a small spanner.

Remove the plastic cap by unwinding the screw

Lockshield spindle

Adjust the Lockshield valve by turning the spindle with a spanner

Step 3

Now all of the valves are fully open; you need to switch on the heating system and write down the order in which the radiators heat up. The one closest to the boiler will heat up first, and the one furthest away will heat up last.

Startup order (click to enlarge)

Step 4

Switch off the heating and allow the radiators to cool down. Go to the first radiator on your list, close the Lockshield valve and then open it by one-quarter of a turn.

You should now have the TRV/wheel fully open and the Lockshield partially open.

Switch on the system and wait for the radiator to warm up and take a temperature reading from the pipe just below the TRV/wheel. Now take another reading from the pipe by the Lockshield valve at the opposite end of the radiator. Now adjust the Lockshield valve with a spanner until there’s a difference of between 11° and 13° between the two readings.

You may need to wait a few minutes after each adjustment before taking the temperature reading as it will take a short while for the rad to heat up.

Step 5

Now repeat this process for each of the remaining radiators on your list. As you progress further away from the boiler, the Lockshield valve will need to open slightly more.

It’s not uncommon for the Lockshield Valve in the first radiator to be open around one-quarter of a turn, while on the last radiator, it may need to be fully open.

Haven’t Got a Thermometer?

There is a workaround for those of you who don’t own a thermometer.

You should open the Lockshield valve on the first radiator by one-quarter of a turn.

Now open the Lockshield valve on the last radiator on your list.

Each radiator in between should have its Lockshield valve opened slightly more than the previous radiator.

For a small flat or house with five radiators, it will look something like this:

  • Lockshield 1 – 25% open
  • Lockshield 2 – 35% open
  • Lockshield 3 – 50% open
  • Lockshield 4 – 75% open
  • Lockshield 5 – 100% open

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How Often Do Radiators Need Balancing?

You should only need to do this once.

However, you will need to repeat the process if:

  • You install a new boiler
  • You add an extra radiator to the system

Radiator bleeding should be done more frequently, older systems that allow lots of air into the pipework should be bled once per year.

More modern and efficient systems may only need bleeding every few years or so.


Balancing means that all the radiators will heat up at the same rate.

If you would prefer one room to heat up faster than the others, then open the Lockshield valve on the rads in that room slightly more.

If you have rooms that aren’t used very often, you can delay the radiator warm-up time by closing the Lockshield valve slightly more.

Still Experiencing Problems With Your Radiators?

The process of radiator bleeding and balancing solves the most common issues such as cold spots and slow warmup times.

If you’re still experiencing issues, your next step is to powerflush the system. This project involves jetting the entire central heating system with water and chemicals to remove sludge and rust that could be blocking pipes and radiators.

If powerflushing doesn’t help, the next steps involve replacing radiators, pipework or boilers.


Don’t Want to Balance the Radiators Yourself?

We don’t blame you.

This type of work is often done by plumbers, heating engineers and handymen.

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