Balancing your radiators can improve the comfort of your home and reduce your energy bills.

Read on to find out why balancing your radiators can lead to a more energy-efficient home, how to spot unbalanced radiators, how to do it yourself, and much more.

Radiator balancing basics

What is radiator balancing?

Radiator balancing is the process of ensuring your radiators heat up each room of your home at roughly the same rate.

This is done by measuring the heat output of each radiator and adjusting its valves, so all rooms reach the desired temperature at approximately the same time.

• When radiators are ‘balanced’, each room reaches its target temperature around the same time.
• When radiators aren’t balanced, some rooms in your home may get too hot while others remain too cold.

Balancing radiators might sound a bit complex, but it's really about patience and making small adjustments. The result will be a more comfortable home with an efficient heating system.

Why should you balance your radiators?

Unbalanced radiators can cause some rooms to get too hot while others remain too cold. This can be uncomfortable and inefficient, as you may have to turn the thermostat up to compensate for the cold rooms.

Balancing your radiators can:

• Reduce your home’s energy usage
• Reduce your energy bills
• Prolong the life of your boiler
• Heat up your home more evenly
• Heat up your home faster
• Reduce knocking or ticking noises from the radiators
• Improve your overall comfort

You may also need to balance your radiators if you have new radiators or piping fitted. This is common when installing a new heating system such as a heat pump.

Recognising unbalanced radiator symptoms

If you notice any of the following, it could be a sign of unbalanced radiators:

• Inconsistent room temperatures
• A radiator taking longer to heat up than others
• Cold spots on the radiator
• Knocking, ticking or gurgling sounds coming from a radiator
• Unexpected increase in your energy bill
• Boiler short cycling (when your boiler turns on and off frequently)

How do radiators become unbalanced?

A home's radiators don’t naturally drift out of balance over time. It usually happens for one of the following reasons:

• The central heating system has been drained and refilled
• A new boiler has been installed
• New radiators have been fitted
• New pipes have been fitted
• Radiator valves have become worn out
• A room’s insulation properties have been altered

How to balance a radiator heating system

Balancing your radiators is a relatively simple process that doesn’t take too long to do.

Tools you’ll need:

To balance a radiator, you’ll need the following tools: ‍‍

‍Radiator bleed key: This is used to turn the small valve found at the top of the radiator and let out any trapped air until water starts coming out.

Lockshield valve key or adjustable spanner: You can use either a specialist lockshield key or an adjustable spanner to adjust the radiator’s lockshield valve. This valve controls the flow of water into the radiator and is used during the balancing process to regulate flow. ‍

Screwdriver: You’ll only need this for older radiators that have a screw-type bleed valve instead of the more common square or hexagonal valve. ‍

Digital thermometer or multimeter with thermometer: This is used to measure the temperature of the water flowing into and out of the radiator.

Step-by-step radiator balancing guide for UK homes with a thermometer

WARNING: Radiators can get very hot. Take care when adjusting your radiators.

1. Turn off the heating and allow radiators to fully cool: This will help you to get an accurate read on which radiators heat up first when you turn the heating back on.  

2. Open all radiator valves fully: Use a radiator key to open both valves on each radiator fully by turning them anti-clockwise. This will allow maximum flow through the radiators.

3. Turn the heating back on and note the order of radiators heating up: The radiators nearest the boiler will usually heat up first. Write down the order that all radiators heat up for reference later.

4. Turn the heating off and allow them to fully cool again: Once you’ve noted down the order in which they heat up, let the radiators fully cool down again before adjusting the valves. This will ensure you’re starting from an equally cold temperature across all radiators.

5. Start with the radiator that heats up fastest: Go to the radiator that you previously noted had heated up the fastest. Close its lockshield valve (the one nearest the floor) fully by turning clockwise.

6. Partially reopen the lockshield valve: Reopen the lockshield valve on this radiator by a quarter turn anti-clockwise to restrict flow to this radiator.

7. Balance the temperature across the radiator: Once heated, take temperature readings by placing the thermometer directly onto the lockshield valve and on the opposite side of the radiator. Then adjust the lockshield valve until there’s a 12C difference between the two sides (this is considered the optimal temperature difference for efficient radiator performance).

8. Repeat the process on all remaining radiators: Work through the radiators from fastest to slowest heating, adjusting their lockshield valves to balance flow and achieve a 12°C temperature difference.

9. Check the system is balanced: Once all radiators are adjusted, turn on the heating and check all radiators heat up at the same rate. Then make any small tweaks as needed.  

How to balance radiators without a thermometer

WARNING: Radiators can get very hot. Take care when adjusting your radiators.

Don’t have a thermometer to hand? It’s less precise and requires a bit more trial-and-error, but you can still balance your radiators by following these instructions...

1. Turn off the heating and allow radiators to fully cool: This will help you to assess which radiators heat up fastest when you turn the heating back on.

2. Open all radiator valves fully: Use a radiator key to turn both valves on each radiator anti-clockwise to open them fully.

3. Turn on the heating and note the order the radiators heat up: Make a note of which radiators heat up first. The ones closest to the boiler tend to be fastest.

4. Turn off the heating and allow the radiators to fully cool: Let the radiators fully cool down again before adjusting the valves. This will ensure you’re starting from an equally cold temperature across all radiators.

5. Start with fastest heating radiator: Go to the radiator that heated up fastest first.

6. Completely close its lockshield valve: Use the radiator key to completely close the lockshield valve (near floor) by turning it clockwise.

7. Partially reopen the lockshield valve: Reopen the lockshield valve by slowly turning it anti-clockwise, about a quarter turn.

8. Feel the temperature difference along the radiator: Once heated, feel along the radiator pipes to determine if there’s a noticeable temperature difference from the lockshield valve to the opposite end.

9. Adjust the lockshield valve based on the temperature difference: If the temperature feels uneven, keep adjusting the lockshield valve slightly until the temperature feels evenly distributed across the whole radiator.

10. Repeat the process on all remaining radiators: Work from fastest to slowest heating radiators, adjusting lockshield valves until the temperature is evenly distributed.

11. Confirm a balanced system: With all lockshield valves adjusted, turn on the heating and feel the radiators to ensure they heat up at the same rate.

Additional information

What to do if radiators remain unbalanced

If your radiators are still unbalanced after going through the above steps, check the following:

• Double check that all radiator valves are fully open. Sometimes a partially closed valve can restrict flow and prevent proper balancing.
• Try closing lockshield valves more than a quarter turn to further restrict flow to radiators that heat up too quickly.
• Check if there’s an underlying issue preventing balancing such as a faulty pump, air locks in the system or sludge buildup. These may need professionally servicing.
• Check that the radiators are bled properly and not retaining air pockets which can create cold spots. Rebleed any stubborn radiators.
• Balance radiators on the lowest floor first, then move up floor by floor. Gravity makes upper floor radiators harder to balance. ‍
• Use thermostatic radiator valves (TRVs) to control room-by-room temperatures if balancing the entire system proves difficult.

You may need to get a professional heating engineer in to inspect the system if your own balancing efforts fail.

Why balance radiators at 12 degrees?

Balancing radiators to a 12C temperature difference between the supply and return pipes is a common industry practice. This ensures optimal water flow through the radiator, resulting in efficient heat transfer.

If the temperature difference is too low, it may mean water is flowing too slowly, reducing how effective it is at emitting heat. Too high a temperature difference can lead to inefficiencies and potential overheating.

12C also helps in achieving the desired return water temperatures for condensing boilers, improving their efficiency. Although systems can operate within a 10-15C range, 12C is often considered the sweet spot for performance and efficiency.

How often should you balance your radiators?

Ideally, radiators should be balanced when they’re first installed. After that, radiators shouldn’t need regular adjustments.

That said, it's a good idea to check them before winter to make sure they’re operating efficiently. You might also want to check them if you've made changes to your heating system or if you notice any inconsistencies in room temperatures.

Should you balance or bleed your radiators?

Radiator balancing and bleeding are two different ways to maintain your home heating system:

• Bleeding radiators involves releasing trapped air from inside the radiator and pipes and allows hot water to flow freely again. This should be done annually and any time a radiator is cold at the top.
• Balancing radiators involves adjusting the thermostatic valves to regulate each radiator's heat output and ensures uniform heating across rooms.  

How long does radiator balancing typically take?

The time it takes to balance radiators can vary depending on the size of your home and the heating system used.

Balancing a single radiator should take around 10 to 20 minutes, once you're familiar with the process. Then it really depends how many radiators you have in your home.

Here's a rough estimate:  

• 2 bed flat: 1-2 hours
• 3 bed house: 2-3 hours
• 4 bed house: 3-4 hours
• 5+ bed house: 4+ hours

Can you balance radiators yourself or should you seek a radiator balancing service?

Balancing radiators is a relatively simple and safe process if you follow the recommended guidelines. Anyone who’s comfortable with a bit of light DIY should be comfortable balancing radiators.

But if you’re unable to balance your radiators or it doesn't resolve your heating issues, it may be worth speaking with a heating specialist.

Balance radiator valves and their types

Different types of valves could be attached to your radiators, depending on the age of your home and the type of radiator installed.

• Lockshield valves are usually located at the bottom of radiators and control water flow. They're adjusted incrementally to regulate how much hot water enters each radiator. This is the main valve used when balancing radiators.
• Thermostatic radiator valves (TRVs) are usually at the top or side of radiators. They allow you to control the radiator’s output temperature. TRVs should be fully opened when balancing lockshield valves. ‍
• Manual valves are traditional valves opposite the lockshield valve for on/off control. They should be fully opened, then locked during balancing.

What is an automatic balancing thermostatic radiator valve?

An automatic balancing thermostatic radiator valve (AB-TRV) is a type of valve that combines both balancing and temperature control features.

Its built-in lockshield-type valve automatically regulates water flow to maintain the target 12C temperature difference across the radiator.

It also senses the room's temperature - if the room gets too warm, it'll reduce the water flow and if it's too cool, it'll let more hot water in.

How radiator balancing impacts energy efficiency and savings

Balancing the radiators in your home can significantly improve your heating system's energy efficiency and save you money.

Radiators work most efficiently when balanced, reducing the amount of time the boiler needs to run to heat the home. This results in less energy use and lower bills.

Also, when rooms are heated evenly due to balanced radiators, you can lower the thermostat without any loss of comfort. This also reduces boiler runtime and saves energy.

To find out the type of energy efficiency measures are best for you, and to discover which grants and payment options you’re eligible for, get your free energy improvement plan from Snugg.