How to Drain a Central Heating System

how to drain central heating system

How to Drain a Central Heating System
draining combi boiler

Sometimes you may need to drain your central heating system to repair leakages in the system.

To drain your heating system thoroughly, it is good to repair more than one radiator.

It will help you to ensure that there will be no chance of getting water leaking out in the future from the system.

Keep in mind one thing that if you start draining your system completely, some boilers won’t work during this period.

Before you begin to drain your radiators, the good idea will be switching off the power supply to the boiler first.

It will prevent scalding hot water from leaking and causing any injuries or damage. boiler kettling

If you’re using a conventional heating system, the first thing you’ll need to do is isolating the water flowing into the water tank before you switched off the boiler.

On the other side, if you’re using a combi boiler, you can just simply switch off the boiler and start draining water once it is cooled down.

If the radiator needs draining, you can follow these simple steps to drain your heating system and make the radiators run more efficiently.radiators


 Draining the Radiator:  

  •         Check the radiator, including the drain-off ball valve.
  •         Open the bleed valves carefully.
  •         Thoroughly drain the radiators.
  •         Complete the draining process by ensuring everything is put back together correctly


Check the radiator including drain off valve.valve

To get started, check the radiator located downstairs in your house and find the drain-off valve on it.

Then, connect a larger piece of hosepipe to the drain-off valve with the help of a jubilee clip.

If the hosepipe doesn’t seem tight fit on the valve, then you’ll require to use a jubilee clip.

However, the clip is good enough to use as it stops the hosepipe slipping off and prevents dirty water from flowing out all over the floor.

You can tight the jubilee clip by using a flat-head screwdriver.

Make sure that the hosepipe is long enough to reach outside of the property to drain the water out. Although, the chemical located inside the inhibitor is more likely to kill off any plant life, so avoid putting the end in your flower bed.


Open the bleed valves carefully.boiler valve

When you open the upstairs bleed valves, wait for 15 minutes to drain the water.

After 15 minutes, try to open a bleed valve slowly on one of the radiators downstairs.

If you see the water begins kicking out, then start immediately tightening the bleed valve back and wait for another 10 minutes.

In the meantime, if you hear something that the system sucks the air, you’re fully safe to open the bleed valve and then do the same for other remaining downstairs radiators.

It will ensure that the last bits of the water are out of the system.


Thoroughly drain the radiators. 

Ensure in your house that all the radiators’ valves are open and check it around in your house.

Then, go to the radiator with the attached hosepipe and open the valves.

You will see all the water starts draining out.

If you want the water draining out more effectively and quickly, go upstairs again and open the bleed valves of all the upstairs radiators.

While doing this, you will hear the air is getting sucked into the system.


Complete the draining process

When the water stops flowing out from the hosepipe, and you’re assured that the vast majority of the water is drained out of the system, then go back to all of the radiators and tighten bleed valves properly.

With the help of the hosepipe close the valve on the radiator and remove the jubilee clip, later take off the hosepipe.

I’ll highly recommend you to be aware of spilling out water when you remove the hosepipe that there might be a little bit of water waiting to spill out.

So, prepare by having a container ready to catch it and avoid the water spilling out.


Final Words 

Before starting draining your central heating system, you must switch off the boiler power at the mains electricity supply. 

If not, this may cause you an injury and damage your heating system as well. 

For more information and help on Draining your Central Heating System, fill in our contact form, and we will contact you as soon as possible to help with your query.

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