How to Flush a Central Heating System

How to guides

As we make our way into the colder months, you might suddenly find that your central heating system isn’t working as well as it should. This could be down to a number of reasons, including needing to bleed your radiators, or it could be an issue with your boiler. But, it could also mean that you need to flush your central heating system.

Learn more about flushing a central heating system below. 

The Importance of central heating power flushing

Over time, your central heating system can accumulate a range of contaminants such as sludge, rust, and scale. Power flushing removes these contaminants from your central heating system, pipes, and boiler, ensuring performance when you need it most. 

Power flushing your central heating system means that you won’t get caught out with a poorly performing system, or be completely without heat, in the middle of winter. If you haven’t flushed your system for a while (or maybe you’ve just moved into a new home), consider doing a central heating flush before winter hits. 

How do I know if my central heating needs flushing?

When your central heating system is blocked with various contaminants, it can result in a poorly performing system and, in extreme cases, can cause damage to the system. 

Some of the signs that you need to flush your central heating system include:

  • Radiators get cold spots, usually near the bottom

  • Radiators don’t get hot, even if the pipes do

  • Radiators take a long time to heat up

  • Radiators need frequent bleeding (learn how to do this here)

  • Discoloured water when radiators are bled

  • Leaking radiators

  • You boiler switches on and off

  • Your boiler produces unstable temperatures

  • Frequent boiler breakdowns

  • Whistling noises from the boiler

How often should I flush my central heating?

A central heating system should be flushed every 5-6 years, on average. Although, it will depend on the materials your radiators are made from, as well as the age of and type of boiler you have. 

If your radiators are less than 4 years old, they shouldn’t need to be flushed. However, if you’re having consistent heating issues, it might be a sign that there’s something wrong with your central heating system. Get it checked out by a qualified heating engineer to be sure.  

If your radiators are 5 years old or more, you should consider flushing them every 5-6 years. In some cases, depending on the quality of materials that your radiators are made from, you could get away with flushing them every 8-10 years.

How to flush a central heating system

Unless you know what you’re doing, a central heating flush should only be carried out by a qualified heating engineer. Lack of knowledge in this area could cause damage to your home.

  1. Turn off your heating and let it cool down for at least an hour.

  2. To protect your floors, spread out some old towels or sheets around your working area.

  3. Turn off the thermostatic radiator valve (TRV) by turning it to 0 or off. 

  4. Then remove the plastic cap on the lockshield valve, and use a wrench to turn the valve off clockwise. (Not down how many turns this took as you’ll need it later to rebalance the system).

  5. Drain the radiator by placing a bucket underneath the TRV, Loosen the nut that joins the valve to the radiator, then use your bleeding key to open the bleed valve. This will allow water into the radiator which will help water to flow out.

  6. Collect everything that comes out in the bucket, then further loosen the lockshield valve to let more water out. Close the bleed valve with the key once finished.

  7. Remove the radiator from its brackets.

  8. Take the radiator outside to flush it out. Place your hose onto the pipe inlet and turn on the water to flush out any sludge. You can also move the hose to the inlet on the other side to ensure a proper clean. 

  9. Reconnect your radiator using the instructions above in reverse order. 

Central heating maintenance and servicing in Newcastle

Home Assist offers central heating maintenance and servicing in Newcastle and across the North of England. Our qualified heating engineers are available for a variety of central heating maintenance services, including central heating flushing. 

Get in touch with us today for more information about our central heating maintenance service.

Scott Flannigan

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