Hey, whats the best way of draining just enough out of a sealed system with a combi boiler. To change an up stairs rad valve. I presume I dont need to drain the whole system for this. Thanks for any help.
Draining sealed system to change rad valve on upstairs rad.
- Thread starter Fredstudio
- Start date
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Hey. Find the drain cock on downstairs rad pipework, or maybe under boiler if fitted downstairs. Fit a garden hose on it, and turn the square end with pliers. Open a couple of upstairs rad bleed valves to help matters. 
Thank you do I just need to open the bleed valve on the rad I have to swap the valve on?
Yes, best to. Ensures that you don't get a vacuum forming in the rad whilst draining down. No nasty wet surprises.
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Is it just the bleed key on the upstairs rad I need to change the valve on I need to open then realy.
I usually open 2 or 3 whilst draining. Breaks the vacuum, and drains much faster. Just don't open any downstairs.
Ok thanks and the fill back up do I just check rads down stairs havent lost any water then bleed rads upstaits and fire up boiler making sure all rads get hot.
It's best to refill the system to approx 1.2Bar, then bleed all rads. Depending on how much air comes out of the rads, you will need to return to the boiler after bleeding every 2 or 3 rads, to repressurise back to 1.2 Bar. You need to maintain some pressure in the system to drive the air out whilst bleeding, as pressure is lost during bleeding.
When finished bleeding all rads, check that you have 1.2Bar, and switch on.
Note. Always check for correct boiler pressure with system cold.
When finished bleeding all rads, check that you have 1.2Bar, and switch on.
Note. Always check for correct boiler pressure with system cold.
Great answer and a great help as I have discovered a leaky return valve and a leaky radiator so I have to change the lot. The radiator is 1590mm x 600mm so I will buy a 1600mm and I suspect the 10mm can be taken up at both sides.
My boiler (combi) is at head height in the downstairs kitchen so I will drain from there so all the top rads will drain.
I have never had a combi system before so I'm not sure how to add inhibitor but I suppose you just undo the plug at the top of one of the rads when drained and pour it in using a funnel.
My boiler (combi) is at head height in the downstairs kitchen so I will drain from there so all the top rads will drain.
I have never had a combi system before so I'm not sure how to add inhibitor but I suppose you just undo the plug at the top of one of the rads when drained and pour it in using a funnel.
Hi
Glad it helped!
If you have the more modern rads with 1/2" plugs at the top for bleed vents, you can either use a bit of hose and a funnel, or one of these.
http://www.screwfix.com/p/no-nonsense-1ltr-filling-kit/98940?_requestid=1980115
One fitting screws into the top of rad, the other replaces corrosion inhibitor bottle cap. Hose to join the two.
Glad it helped!
If you have the more modern rads with 1/2" plugs at the top for bleed vents, you can either use a bit of hose and a funnel, or one of these.
http://www.screwfix.com/p/no-nonsense-1ltr-filling-kit/98940?_requestid=1980115
One fitting screws into the top of rad, the other replaces corrosion inhibitor bottle cap. Hose to join the two.
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