Correct way to flush central heating system

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I've had plenty of problems with the heating/boiler since buying this house earlier this year. At one point part of the pipe work was completely solid with sediment. The gas engineer found it and cleared it, but I'm sure plenty more lurks in the system.

My plan is;

Shut off water to F&E tank
Fully open all rad valves
Connect hose pipe to lowest drain off point and open
Let the system completely drain down and close drain off point
Clean F&E tank
Fill F&E tank with Sentinel X800 and turn water back on

*Do I need to run the heating at this point*

Leave in system for a couple of hours
Open drain off valve again and just let the system refill and flush through until water is clean then close drain off valve
Add Sentinel X400
Leave for a couple of weeks until I need to take rads off to fit skirting boards
Then after that couple of weeks repeat emptying mode, take off rads, hose them out, refill system with X100.

Does this sound ok? Have I missed anything? And do I need to run the X800 with the heating on?

Thanks very much
 
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You should vacuum out the F&E tank with a wet and dry before you drain down, it'll be full of crud and you don't want to be drawing that into you system.
 
You should vacuum out the F&E tank with a wet and dry before you drain down, it'll be full of crud and you don't want to be drawing that into you system.

Could I bale out the water into a bucket?

Does everything else look ok to you?

thanks
 
You can bale it out with whatever you want, as long as you dont open the drain while theres still a lot of crud in the F+E tank.

Any non acidic cleaner needs the heating to be run to heat up the cleanser and to circulate it through all the pipes and rads evenly.

after a few hours like this (x800 is strong and not a drop of it should be left in the system) it should be drained, but not by opening drain valve and letting F+E run, this will only remove a very small amount,

you need to open drain, shut off F+E feed, wait till it all empties, then open all the bleed points on the rads to allow air into them so as much water as possible leaves the system. You then fill vent+circulate again, you then drain again using above proccess until you could fill a large coke bottle or similar with whats beeing drained off and its completely clear and colourless, if theres still a dark tint or a colour to the water, you keep repeating untill it looks like you've filled the bottle with tap water. then you can refill with water+inhibitor.

I also wouldnt encourage leaving the system empty for any length of time as the rads will simply rust out and the next time you fill and circulate you'll be back to square one.
 
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Another thing to remember is that if the drops are from above to all the downstairs rads then all the rads that are not drained including the pipework leading down to them will still be full of water and ultimately X800 also.
 
Thats a good point, and also missed by many installers "flushing" drop fed systems.
 
Another thing to remember is that if the drops are from above to all the downstairs rads then all the rads that are not drained including the pipework leading down to them will still be full of water and ultimately X800 also.

What's the solution to this? Do I have to take all the rads off?
 
Properly fitted drop fed should have drain valves on all those rads, you would connect hose to each in turn and empty fully including the drop pipes.

Many however do not. Rad off and flush manually is an option, and open pipes into a bucket to empty the drops. but you will still have to do the whole lot a few times to be sure to eliminate all the cleanser.

This is where powerflush/mains fluch can be handy as they can circulate the water round such a circuit till its clean and free from debris+chemicals. Again tho would depend on pipe size feeding rads as to how much rubbish you could potentially blow out of the rad/pipework. More often than not microbore wont allow for high enough flow rates to move sludge from the bottom/middle of the rads
 
If you don't have drain offs on each rad it's the ideal time to fit them
T ;)

Even if you buy the valves with them already on.
 
Two of the 3 downstairs do have drain offs. The third is a new corner column rad which does not, and there's no way I'll get that off on my own. Weights a tonne. :/
 
One option would be to plug the cold feed and open vent that way you can change one valve for a drain valve one.
 
You can bale it out with whatever you want, as long as you dont open the drain while theres still a lot of crud in the F+E tank.

Any non acidic cleaner needs the heating to be run to heat up the cleanser and to circulate it through all the pipes and rads evenly.

after a few hours like this (x800 is strong and not a drop of it should be left in the system) it should be drained, but not by opening drain valve and letting F+E run, this will only remove a very small amount,

you need to open drain, shut off F+E feed, wait till it all empties, then open all the bleed points on the rads to allow air into them so as much water as possible leaves the system. You then fill vent+circulate again, you then drain again using above proccess until you could fill a large coke bottle or similar with whats beeing drained off and its completely clear and colourless, if theres still a dark tint or a colour to the water, you keep repeating untill it looks like you've filled the bottle with tap water. then you can refill with water+inhibitor.

I also wouldnt encourage leaving the system empty for any length of time as the rads will simply rust out and the next time you fill and circulate you'll be back to square one.

Comprehensive & informative post SGM, thanks for taking the time.

I & many others have successfully flushed a system with X800 & mains water. This is referred to as a 'Mains Water Flush'. For open vented systems you could plug the cold feed at the F&E tank & connect up the mains & expansion pipe as detailed in CH FAQ - Blocked cold feed..... ;)
 

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