Rad change/system drain in a combi boiler
Need to change a radiator which involves simple pipework change (it’s on push-fit) but means draining the heating system.
From what I’ve found it ‘should’ be as simple as;
Turn off combi boiler
Open all rad valves
Hose and jubilee clip to lowest drain valve
Open up drain and rad bleed points
Drain past the top floor
Do pipe work
Close all bleed valves
Fill up system again’
So, anyone done it?.is it that simple on a combi, any pitfalls?
Worth draining whole system and doing fresh inhibitor?
Any comments appreciated
CheersPosted 7 months ago
I think You will need to pressure the rad system on most combo setups which requires a specific pipe in some casesPosted 7 months ago
Combi has a filling loop for re-pressurising, which I assume is the same thing?Posted 7 months ago
YepPosted 7 months ago
If you get lucky on a combi system, once you’ve dropped off the 1.5bar of system pressure the rest of the system normally ‘Hangs’, allowing you to do minor alterations without draining the whole system, then just top up and bleed.
I’d close all rad valves 1st, then you’re only draining the pipework rather than all the rads. once finished, go round and just check/bleed rads to get ride of air pockets.Posted 7 months ago
My (many) experiences are the same as Blazin.
Much easier than a system boiler which requires rubber bungs or half tennis balls.Posted 7 months ago
rubber bungs, tennis balls??!!
Good shout on the closing valves to just drain pipes.Posted 7 months ago
That said on a system that’s had nothing done in 5 years is it worth draining and refilling/new inhibitor anyway?
Or is that pointless without a powerflush?
Close off all the rads in the system on the thermostatic valve and outlet valve of the radiator.
Turn boiler off, crack the nut on the rad side of either of the 2 valves on the rad you want to remove (if you dont have a drain down valve) have a bucket to catch any water, remove bleed screw for faster draining.
Remove rad or whatever work you are doing.
Refit, tighten nuts.
Repressurise system, open rad inlet(thermostatic valve) handy to have a fitting on the bleed pipe if filling the system on your own with a hose into a bowl or bucket, otherwise you end up with water all over the floor.
Turn off filling loop
Refit bleed valve.
I normally add inhibitor to one of the towel rails in the system as they normally have a top mounted nut, rather than a side entry or having to use a special tool in the filling loop.
Always worth doing, as it stops the build up of sludge and scale and protects the boiler.
Start the boiler and check the rads all get warm after opening the valves, rebleed the removed rad.
Plenty of towels help aswell!Posted 7 months ago
Also keep an eye on the pressure gauge on the boiler after refilling.
Makes it easy to identify if you have a leak after any work you have done.
A lot of leaks occur when the system is off and not circulating through the systemPosted 7 months ago
Thanks all, top tips.Posted 7 months ago
Was feeling positive until someone mentioned the ‘L’ word – Guess that’s the plumbing equivalent of the ‘p’ word!
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