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Top Tips For Draining Central Heating Systems

My top tip and best advise for draining central heating systems is don’t try this at home! Your much better off getting a professional in like my self if you’re in the Portsmouth area. It’s not that it’s a hard job, any competent DIY guy can drain central heating systems. The thing is any mistake can be costly and mistakes are often made doing this. A plumber drains central heating all the time and so is experienced, a builder or DIY guy isn’t, also a professional plumber has insurance if they flood your carpet! If you still want to do it yourself ok here are some tips worth considering before you start.

Before Draining Central Heating Tips

Before draining central heating systems ensure its a vented system the type with an expansion tank in the loft otherwise known as a header tank (with toilet ballcock). Combi boiler type heating systems are much trickier and are best to call the plumber.

  1. Make sure the boiler or pump cant start up by switching every thing to the off position and zero the thermostat dial , remember to put back to how they were.
  2. Prepare tools , 2 trays (that fit under !) , bucket , hose , rags/towels (and a friend incase any mistakes are made).
  3. Remember to take up the loft a broom or something to put across the tank and a bit of string to tie the bull cock up.
  4. Inspect the ball if there is water inside replace it they only cost a few pennies.
  5. Open the upstairs bleed valves slowly to allow the water to run out faster when the pressure has dropped open the downstairs ones.
  6. When the water has stopped it doesn’t mean the system is empty. there could be an air lock , read on.
  7. When the water has stopped go back up the loft with a bucket a scoop and rags/towels , as you will probably need to clean the gunge out of the bottom of the tank . taking care not to let any go down into the system.
  8. Now to check there is no air locks untie the stop cock and let a good bit of water run down the pipe , a few seconds you should hear your mate shout up . If so good no airlocks the system is drained tie it back up go down .

If you have an air block you can squirt water back up the way from the tap via the hose , of course remembering to close the bleed valves first.

Refilling After Draining A Central Heating System

Refilling after draining a central heating system is a bit of a reverse process but still requires a bit of thought to avoid any problems.

  1. Close the drain cock , close all the bleed valves .
  2. Go back up the loft and fill the expansion tank remembering to take the inhibitor with you. Tip it in slowly as the tank fills so it can get in the system not just the tank !
  3. Wait up there untill the ballcock has stopped the water to make sure it works properly. OK, finished up there put the lid on .
  4. Go to the downstairs radiators and bleed them one by one and then do the upstairs .
  5. Be sure every thing is tightly closed , switching all back to how it was then fire up the boiler .
  6. Turn the thermostat up , to bring the system to heat up it will probably make knocking and creaking noises.
  7. Now you can try to bleed the rads of any air left in them.
  8. Lastly when the the system has fully heated up cheak for any leaks.

Thats it job done well done!