Cleaning combi CH system

[Earl Kella]

If I put the cleaning solution into the system how is the best way to 'flush' the system?

1. Pressurise and run the boiler to circulate the fluid (i.e. heating ON)
2. Just leave the cold water inlet feeding water in with a hose connected to the drain

None of the above?

Thanks & regards

Earl

[Ed Sirett]

Both are useful tactics. The best way is to remove each radiator in turn and flush with a hose in the back yard. The in situ flushing with mains water is pretty good at removing the sludge at the bottom of an old rad.

I have no idea why you are attempting this and it may well be the correct course of action. There is also the possibility that you have been told that a problem s due to 'sludge'. You should be aware that some companies (including national ones) have been known to suggest sludge as the default diagnosis when they have run out of other ideas.

[Earl Kella]

Thanks for the replies. I was not sure if I should run the system with cleaner or not, but I will probably just flush with cold before re-filling.

Heating system is only 2 years old and I have just had to drain it to remove a few rads due to plastering. Before re-filling I thought I might give it a clean through.

Only problem with trying to flush with mains water is how to get it to reach the rads at the top of the house and not just come straight out the drain tap at the bottom via the lower rads return feed. I think I will just re-pressurise and then drain a few times.

Regards

Earl

[Dave Plowman (News)]

If the system has had proper inhibitor used from new and isn't leaking it will survive for tens of years with no sludging.

For a steel rad to start corroding requires oxygen in the water, and unless fresh water is being continually introduced there won't be any.

[Ed Sirett]

I'm rather pleased I queried your need to clear out the system which almost certainly will be entirely unnecessary.

You force the mains water through only one rad at a time.

[ceetee]

News to me as I didnt think you were supposed to add inhibitor to Combi system. Just give it the regular drain/refill

-- ceetee

[Dave Plowman (News)]

'Regular' drain/refills are the last thing any central heating system needs. Each time you introduce fresh water it is oxygenated and it's this which causes steel to rust. Then there's also the impurities in the water

- more so in a hard water area.

Inhibiter is a must in *any* system for long life.

[Ed Sirett]

Not only are you 'supposed' to but the instructions may even specify which make to use.