Consumer Advice

How to Drain and Refill a Heating System

How to Drain and Refill a Heating System


Typically, you’ll need to drain and refill your radiators if you wish to move or replace them – or if you are treating corrosion.

First you’ll need to empty out the water, so switch off the central heating and the water supply to stop the system re-filling. Do this by turning off the water at the main stop valve.


Then, attach a hosepipe to the outlet of the first drain valve (it doesn’t matter which, as you’ll need to do both) and lead the hose to the bath, or outside, so that the water can drain away. Unscrew the valve with a spanner, and let the water flow out. To check that all the water has been removed, unscrew the air bleed valve on each radiator, including the one on the hot water cylinder. You can usually find this on the upper two pipes, at the highest point. The system will now be empty, and you might want to remove radiators at this point, take them outside and flush them through with water from a hose.


When you’re ready to refill the radiators, close the air bleed valves and the drain valves, and release the ball valve (found in the feed-and-expansion cistern.) You can also add some anti-corrosion inhibitor at this point, using a funnel. The system will start to refill, and you’ll need to bleed each radiator, starting on the ground floor, and working upstairs. You may need to do the full system twice – don’t forget the air valve on the hot water circuit (which is located next to the hot water cylinder.)


Once the system is full again, switch the boiler back on and go around each radiator to check that there aren’t any leaks, and to tighten any valves as necessary. It’s well worth having a number of old towels on hand for this activity, to preserve flooring and carpets whilst carrying out a potentially messy job!


To avoid these steps entirely, remember of course that Home Appliance Care offers this service at a time to suit you! Leave the job to the experts and retain your peace of mind. Click here to book an appointment, or call our friendly team today on: 0844 248 4591.