How do you drain & flush a Central Heating System?

Question

I know kittens are fluffy but if I can do it then I'll have a go.

Answer 1

For the life of me I don't know why you would want to drain and flush out a central heating system.
Its the one thing you MUST NOT do. Fresh water contains lots of oxygen, which rusts radiators, so no self respecting heating engineer would drain out a central heating system for no reason.
If you are having problems mail me at [e-mail]

Answer 2

At the lowest point of you heating system, you should see some form of tap and spout designed to take a standard garden hose.

1. Attach a hose pipe to this and run it out to a drain.

2. Either turn the water off to the header tank, or use a piece of wood and string to tie the ball valve up. This stops water re-entering the system.

3. Ensure your boiler is switched off, this includes the gas. Youd don't want it firing up with no water.

4. Open the valve that you have attached the hose to.

5. Working from the radiator the furthest from the boiler, undo the bleed valves from each radiator.

6. When the water stops coming from the pipe, close the valve.

7. Close all of the bleed valves.

8. To start the flush, clean out the muck in the header tank - saves it being send through the pipe work. Then let the water flow into the header tank.

9. Once the tank is full, start bleeding the radiators of air starting from the radiator the furthest away from the boiler.

10. Once all radiators have been bled, empty the system as previously mentioned.

11. Once empty and all the valves are closed, add some rust inhibitor to the header tank and refill.

12. Bleed the radiators and turn on the boiler.

13. You may need to bleed the radiators again after the boiler has fired up to remove any residual air.

Answer 3

First find the drain valve which will be somewhere at the lowest point in the pipework. Then locate the feed and expansion tank in the loft. It will be quite small and contain a ball valve. Either turn off the water to this ball valve by using the in line valve close to the tank or if there isn't one tie up the valve so that it will not open to let in fresh water when the water level falls.
Fit a hose pipe to the drain valve and lead it outside.
Open the valve and allow the water to drain out. As the water level in the system falls, open the radiator bleed valves upstairs to allow air into the system. This helps the draining process. When the system is empty close all the bleed valves. Release the ball valve in the Feed and Expansion tank and allow water back into the system and let it run at at the drain. You should have black water coming through. When it turns clear you have a fairly clean system. However there is a lot of black deposits in the radiators. Ideally you should take the radiators off and empty them and flush them though separately. The downstairs ones are the worst.
When you have finished pour in some FERNOX available from Plumb Center or Travis Perkins which will help keep the system clean for a few years.
You may need to bleed air from the centre of the pump as you fill.
Best of luck as you can save yourself at least £150 by doing this yourself.

Answer 4

Cleaning Central Heating System

Answer 5

Flush Heating System

Answer 6

Don't mess with any central heating system at the start of winter. If you are a DIY'er - and I assume you are- then if anything goes wrong you will be in big trouble, trying to locate a plumber at short notice, which is impossible even for Polish ones. .

I strongly recommend you leave this until spring. However I sense that you are flushing this system because it is faulty in some way, and you think that flushing it might help. If this is the case, I'd call a plumber instead of possiblymaking things worse. Of course your system might just need "bleeding"- in which case Joey H's suggestion will put you on the right track.

Answer 7

When you drained the bathroom radiator you should have drained the whole system? You still can, or if you have a drain point connect a hose and leave it running for a while with your mains water still turned on. This will flush the system. To flush it correctly you can buy a radiator flush from Plumb centre or where ever. Take a radiator off again leaving valves on the radiator. turn one valve off and pour flush in from other. when all flush is in radiator turn off the valve this will enable you to turn radiator right way up to fit back on the wall and reconnect. Refill your system with water and bleed as normal. Run your heating for 24 hours,turn it off,turn off your water supply and drain your complete system. When drained repeat filling radiator as you did with flush but this time use inhibitor also available from same place,the inhibitor stays in your system. you should have a much cleaner heating system.

Answer 8

The first step is to disconnect the boiler from the power after switching it off and putting out the fire (if you have a solid-fuel burning boiler).

You now have to turn off the water supply. If you find that your home is without either a switch or central heating drain valve, there is an alternative to keep things under control. Have a piece of wood sitting across the cistern fixed to a piece of string that is keeping the ballcock held together.

On the pipe work, towards the bottom you will find the draincock. Once located, go ahead and connect the extractor hose here.

Make sure you secure it with a clip and then put the other end of the hose in a waiting ‘waste area’.
Once all the above is completed and sufficiently checked, the draincock can be opened which will see the water start to flow through the hose.

The next step is to bleed all your radiators starting upstairs and working your way down. Obviously, ensure that the water levels have dropped to prevent any accidents; it is a good idea to carry a cloth or container around with you just in case water decided to spill out.

After a while you will notice that the water from the hose slows down, when this happens you have successfully completed draining central heating.

Answer 9

I'm with XENON on that one.......
there is no reason you need to do it
as for what another contributor said, i say the opposite-- do not add antifreeze or inhibitor if your system has been around for a while; or you ll end up replacing many parts that never leaked before

Answer 10

you need a special key to unlock your tiny tap on your radiator, open it slightly until you hear hissing air, makesure that you have a bucket ready, keep the air hissing until water comes out then close it. work from the top of the house down. good luck.