How to flush a central heating system

At least once a year a central heating system will need to be flushed out. Also if you have to do any repairs you will need to flush the water out. Boilers will need repairs in case of hard water.

Some of the tools that you will need are: pliers or wrench, water hose, buckets, descaler.

Draining the system

First of all you will need to turn the power off. Go to each of the radiators in your home and place a bucket under the drain valve. Open it and drain the water. if the water is gray then there is no problem. If it’s black then you have some sludge build up and a rusty color means corrosion.

Flushing the system

Close all the valves. Now connect the water hose to the feed tank in the loft. If you have to descale the system, then this is the time. Follow the instructions. After this it’s indicated to start the system and run the boiler on high with all the radiators open for at least a week. Then turn the system off and drain it again, until the water is clear.


Refill the system and run it again and make sure that the valves are shut off. Let the water run down into the boiler. Now is the time to add a scale inhibitor. While filling the system, air will get trapped. Go to every radiator and open each air valve to let the air out. You will have to repeat this step after a week and then after a month to make sure that you have got all the air out.

black radiator water, central heating system, descale the central heating system, descaler, draining central heating system, draining radiator water, draining the water from the heating system, filling a heating system, flushing the central heating system, heating system, home heating system, how to flush the heating system, letting the air out from a heating system