Why should I drain my central heating system?

draining your heating system

Why should I drain my central heating system?

Maintaining your central heating system is just as important as any other household maintenance.

But why is draining your heating system necessary?

Here is our step-by-step guide.

Over time, your radiators can collect sludge and limescale which can block up your radiators and have an impact on their efficiency.

Draining your radiators will therefore be necessary to remove any build-up and get them working perfectly again. The whole process should take anywhere between 30 minutes and an hour.

How to drain your central heating system in 7 simple steps:

STEP 1: Turn off your heating system

This is a safety precaution. Then it is important to wait for the pipe and system to cool down completely before beginning.

STEP 2: Wait for your boiler to cool

If your boiler is run on solid fuel, make sure your boiler is turned off and is entirely cool before you begin draining.

STEP 3: Stop the water supply to your boiler

Before you begin the draining process, cut off the water supply. This will keep the radiator dry while you work through the process. There may be a stop tap for you turn off, or you can tie up the ball valve which is on the top of the cistern.

STEP 4: Find the drain valve

The right radiator is usually on the first floor of your home. On it will be a drain valve. Clip a hose onto the drain valve to let the water run outside.  There are chemicals in the inhibitor, so make sure that the water runs away from your garden if possible. The chemicals could damage the plants.

STEP 5: Bleed your radiators

This is now the moment to bleed your radiators. Open the bleed valve so that the water can run through your system freely. Begin with the radiators at the top of the building to allow the water to run more freely through your heating system.

After approximately 15 minutes, open the bleed valves on the radiators on the ground floor of your house.

STEP 6: Open valve, get rid of water

Make sure that all the valves in your house are open. Open the radiator valve to which the hose is connected and drain your central heating. The time this takes will depend on the type of central heating system you have.

To help quicken the process you can open the bleed valves.

How to bleed your radiators.

STEP 7: Refill and turn on your heating system

Once the process is complete, then it is time to refill the system.

Close all the valves you have opened and let the water fill up the system.

It is important to use an inhibitor in your system to reduce the risk of limescale build-up or corrosion.


If you are uncertain about how to bleed your radiators, or if you need to, then it is always a good idea to leave the dirty work to a professional plumber. What can a plumber do for you? Read more here.