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Central Heating System

How to drain a central heating system

You may have come to a point where you need to do some work on your central heating system. Of course, before you can do this, you need to drain the water from the system. While this might seem like an intimidating proposition, it is something you can do yourself. This article is going to run you through exactly, how you go about draining your central heating system.

Switch the heating system off

When draining your heating system, the first step should always be to switch the system off. For safety reasons, you then need to allow time for the radiator and pipes to cool down. This will usually take between 30 to 60 minutes.

Cut the water supply

There are several different ways you can switch off the water supply. You can opt to completely turn the supply off at the mains, which is usually done by tightening a separate tap or valve with a flathead screwdriver. Although, it is worth remembering that if you choose this method, you will not have access to running water during the period you are working.

With a conventional central heating system, the tank should be isolated, so no new water can get in. The remaining water in the tank can be drained, and the boiler switched off. If you have a combi boiler, you just need to switch the boiler off and wait for it to completely cool down before going onto the draining process.

Locate the radiator with the drain-off valve

The next step is to locate the radiator that has the drain-off valve. As all the radiators drain the water out through this main radiator, it is usually found on the ground floor.

Then, take your garden hosepipe and attach it to the drain-off valve. To prevent leaks, you can either put towels down or attach a jubilee clip to make sure that the hose is securely attached to the drain-off valve.

Open the drain-off valve

With the hosepipe securely fastened at one end and positioned towards a drain in the garden at the other, you can open the valve to begin the draining process. Once you loosen the nut next to the drain-off valve, you should start to hear water rushing through the hosepipe. At this stage, you need to make sure that all the radiator valves in the house are open.

Bleed the radiators and allow water to drain

The idea behind bleeding radiators is to release air that is trapped in the system. This can cause your radiators to distribute heat un-evenly as the areas with trapped air remain cool. This process should be started with the upstairs radiators, before making your way down to the ground floor.

You will know when the central heating system is drained, as there will be no more water coming from the hosepipe. When you get to this point you can get started with the work that you need to do.

Refill the central heating system

Finally, you will need to refill your central heating system. To do this, you must close all the bleed valves and the drain-off valve. You can then switch the mains water supply back on, and your central heating system will start to refill. You will then need to bleed your radiators again, as it is important to remove all the air in the radiators to ensure that they work properly. Although, this time you should start from the ground floor and work your way up.

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Michael Cornish