Draining and refilling combi boiler central heating

3 Jan 2004
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United Kingdom
Greetings All

I have a combi boiling central heating system. I want to drain and refill the system so that I can work on the pipes. What's the basic procedure?

Elsewhere on the web I've seen pages that describe how to drain and refill a central heating system, but they cover vented systems, with footnotes saying "If you have a sealed system, seek professional advice." If I understand things correctly, a combi boiler is a sealed system. Will I really need professional help just to drain and refill it?

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Quinn "The Eskimo!"
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mine is a combi, i can drain it with no problem, i have a "little tap" under the floor (actually i think its called a drain valve) look for one on the lowest point of your sytem and open it up (and obviously turn the boiler off first

you may have


mine is just the "sticky out bit" at the bottom
breezer said:
mine is just the "sticky out bit" at the bottom

Yep, got one of those. I guess my question really is, how do I refill the system. I know where the filling loop is and I've used it to repressurise the system from time-to-time. Is that also used to refill the system? If so, is there any magic, or do I just start filling, wait for the pressure to hit 1.5 bar, bleed a radiator, lather, rinse repeat.

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Quinn "The Eskimo!"
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Thanks for your help with this. This is just a quick note to let you know that last weekend I did the work and, barring fun and games with valve/pipe seals failing as the result of disconnecting the valves from the radiators (the reason I wanted to drain the system in the first place), everything went swimmingly.

btw Just for the record, my combi boiler is a Vokera Excell 96E.

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