Desludging my old system, drain the lot or just enough?

[Niall76]

Radiators in my house are not warming up correctly, they get hot at the top but cold at the bottom. Anyhow, I have some Fernox desludger to add the the system which is an older boiler with hot water storage tank and radiator circuit with a small header tank in the loft.

What I was wondering though was should I drain down the whole system (there is a drain point at the lowest point outside the front door) and the empty the contents of the bottle into the header tank and let it refill itself? Or, should I drain off just enough so that the header tank is empty but the radiators and pipework is still filled and then empty the contents of the bottle into the header tank and let it fill again?

Which would be best to get the chemical into the system and circulating?

It's 8mm microbore pipework and I reckon the chemical will need to be kept in the system as long as is possible to break it all down. Unfortunately the previous owner of the house neglected everything pretty badly.

Does anyone know how long it should be before I expect any noticeable results?

Also, once I have left it in there as long as possible what's the best way to remove it all? Could I just connect a hose to the drain off point and open the valve without tying up the ballcock in the header tank and let it flush through? Should I consider adding a 2nd batch of desludger? And finally, is there anything I should add to prevent build up in the future?

Sorry for the longwindedness of this. Your help is much appreciatted. Thanks

 

[sambotc]

Hi,

If i was doing it, i would drain all the water from the entire system first. You can then inspect the condition, plus your removing a quanity of rubbish/sludge just by doing this.

After this you can add the chemical to the tank (make sure the tank is clean, if needs be give it a good scrub)

Then you can fill up and vent.

If the system is really badly sludged up then you should consider finding the cause of the problem for a long term fix.

Also may be your pump on its way out.

Sam

 

[JohnD]

IMO it's worth giving it a drain, plain water flush and drain again, then refilling with your chemical cleaner. this will mean that any loose sediment will tend to come out in the first couple of drains, and the chemical can get to work on the loosening the more persistent stuff.

Drain it to empty, then refill and circulate with cold water and drain again to get the suspended sludge out. you will see the colour of water go from black to clear when it is fairly clean.

If you can afford another £100, you could get a Magnaclean and fit it on a 22mm return pipe. this will trap any circulating black sediment. You still need the chemical to loosen it. the Magnaclean continue to trap circulating black sediment long after you put the system back into normal use, and only takes a few minutes to empty, with no draining required.

And yes, once you have finished cleaning it, you must refill using inhibitor to prevent further corrosion.

I am not a plumber

p.s. Good point by sambotc about cleaning out the F&E tank. Bale out the sludge into a bucket before your first drain (to prevent it being washed down into the rads) and use a sponge to get out the last of it.

 

[Niall76]

Thanks for the fast replies.

My thinking was I could just open the drain valve and just let it run out and continuously refill - i.e. this should help to wash out a little of the sludge? Is this a bad idea? Very good point about the header tank needing cleaned - I'll do that first.

I think the main problem is that it's just old and was never maintained. Like everything else the previous owner had....

 

[hi-spec plumbing heating]

watch that sludge it's a bugger to get off ya cloths and hands i've had it stain my hands for days.

and it loves carpets.

 

[JohnD]

My thinking was I could just open the drain valve and just let it run out and continuously refill -....

It will tend to find the shortest and easiest route, and run down that, bypassing most of the system entirely.

 

[Niall76]

Aha, yes I can now see that this would happen. Thanks for the info.

I was hoping I wouldn't need to take any radiators off to wash them out? Should the chemical start to move the stuff and I'll feel the radiators getting hotter?

Sorry for being a nuisance.

 

[Niall76]

watch that sludge it's a b*****r to get off ya cloths and hands i've had it stain my hands for days.

and it loves carpets.

knowing me I'd get the last job without a mark and then *bingo* it will indeed hit the carpet....

 

[JohnD]

if you can take out the rads and hose them through, this is a good way of getting sludge out of them. If you can't do this, chemicals and time will gradually loosen some.

The cleaning chemical will loosen sludge remaining in the system so that it is carried around the system suspended in the water. Some sludge settles and hardens in various nooks and crannies. Sometimes the hardened sludge causes blockages. the cleaning chemical loosens this hardened material, provided that it can flow over and through it.

You can then drain out the dirty water, and it will carry with it the suspended sludge.

A Magnaclean will trap the Black (but not other materials) while it is in circulation, so you can monitor if the chemical is continuing to loosen more by observing how much is trapped when you empty it at intervals. by trapping it, you can take it out, and you know that the sludge you have taken out will not be able to re-settle inside the system.

 

[JohnD]

(I like the Magnaclean I fitted in my old mum's system during the summer)

Here you see some sludge collected after a week (after the system had been drained, chemically cleaned, drained and flushed, and returned to service and appeared to be clean)

and you see I cleaned it off the sleeve and collected it in this jar

the amount of sludge is declining, and is now less that a teaspoonful a week. there is now no cleaning chemical in the system, it is just picking up remaining loose stuff. the water now looks clear.