How to balance your radiators

A poorly balanced heating system can add a significant amount of cash to your annual bills.

Many people aren't aware of the impact that a poorly balanced system can have, chiefly that it can drive up your bills during the colder months. You might be unnecessarily cranking up your thermostat or forcing your hot-water pump to work a lot harder to move water around the system; all of this wastes valuable energy.  

How do I know if my heating system is unbalanced?

The telltale signs of a poorly balanced system include some radiators heating up much faster, or getting much hotter, than others in your home.

Another clear sign is if certain parts of your house (such as upstairs) get uncomfortably hot, while other parts stay cool. 

Why do I need to balance my heating system?

The image below shows the impact of an unbalanced heating system on a typical household. In an unbalanced system, when you set the thermostat to 20°C, the upstairs might actually reach 23°C, while the downstairs remains relatively cool. 

As a typical home dweller will spend most of their day downstairs, they'll turn up the thermostat (in this example to 23°C), which will create a comfortable temperature of 20°C downstairs, but superheat the upstairs to 26°C. 

The Energy Saving Trust estimates that turning up the thermostat by just a single degree costs an additional £75 a year in heating costs.

Why is my system unbalanced?

Your system can become unbalanced for a wide variety of reasons.

• Old systems may be filled with sludge and debris, which can cause blockages in some radiators, meaning they take longer to heat up. 
• When radiators are removed and replaced, perhaps during decorating, this can impact the balance of the whole system.
• One of the most common reasons is the misuse of TRVs (Thermostatic Radiator Valves). If TRVs have been fitted to radiators around your home and not adjusted correctly, then this can lead to system-balancing issues. 

How can I check whether my system is balanced?

It's easy to tell if you have inadvertently unbalanced your own heating system with TRVs. 

1. Turn all radiator thermostats to 0.
2. Turn the central heating off and wait for at least two hours for the system to completely cool off.
3. Starting from the radiator furthest from the heating source if you have a combi boiler, or furthest from the water pump (usually found in the airing cupboard next to the hot water cylinder) if you have a heat-only boiler, turn all thermostats to 2.
4. Starting from the radiator furthest from the heating source, check if all radiators get hot evenly across the radiators at the same rate.

If they don’t, the system is not balanced properly and we would recommend that you call a Which? Trusted trader to assist with what will be a much more technical method of balancing your heating system. 

How a heating engineer will balance your system

1. Turn off the boiler for at least two hours for the system to cool off.
2. Turn on the boiler from cold.
3. Measure whether there is a flow differential (DeltaT) of at least 20°C at the boiler.
4. Measure whether the return temperature is below 55°C (this is essential for condensing to occur, and for your boiler to be operating at its advertised efficiency).

If the flow differential is less than 20°C, or the return temperature is higher than 55°C, then the system is either unbalanced or the radiators are too small. Either way, you will need a heating engineer to fix it.

A heating engineer will first completely drain the system and remove any air pockets by bleeding the radiators. They will then refill the system with all of the radiator valves fully open. The next step will be to adjust the valves on the radiators that get hottest the fastest. This it to restrict the flow of water to the radiator and even out the spread of heat to the rest of your home.  

Costs for this will vary between £100 and £200, but expect the heating engineer to take at least half a day to complete the work. 

If you're ready to call in a heating engineer to balance your radiator, you can use our Which? Trusted Traders search tool below to find an accredited trader near you. All of our traders have been vetted so you can trust them to do a great job.

If you're planning on giving your heating system an overhaul, make sure you read our five tips to reduce your heating bills before you do. 

And if you decide it's time for a new boiler, make sure you buy from the best boiler brands.