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Ashley

Central heating flush?

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Hi all.

 

My GFCH system must be almost 60 years old and to my knowledge has never been flushed.  have brown water in the header tank and the rads do not heat at the bottom. I have arranged to hire a flushing machine from HSS Hire for next weekend but now starting to worry that flushing the system may expose corrosion in the system which in turn may cause leaks?? What I would like to know is if I am right to  be concerned about this please or should I go ahead with flushing out the system?

 

Many thanks 

 

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What sort of radiators are they ..? It’s likely that you have all sorts of crud in the system and I would be more concerned that a flush will dump muck into the boiler heat exchanger and block that so I would think a bit before flushing. 

 

Assuming it’s a one pipe system, you may need to do some clever work with the pump to get it to clear through these sorts of rads as it’s not designed to do that - do you know where all the drain offs are on the pipework to start with ..?

 

Initially you may be better draining the lot down and putting a magnaclean or similar in the feed to the boiler first and then adding a central heating cleaner. It will allow you to drain and dose the system too - easier than working in an attic in the header tank ..!

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Thanks for your great advice Peter. Mainly single panel rads with a couple of single convector rads. 

Don't know where the drain offs are so will try and get someone to have a look for me.

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Hopefully your drain cocks are accessible - I've seen some crazy settings for them half buried in concrete, or as in my last house, so low that you could not actually get anything underneath or even a hosepipe on to drain out of. 

 

Edited by curlewhouse

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Well I have found 2 drain cocks anyway!

Plan B is to remove the radiators and flush them manually until I can get a magnaclean filter  installed. Hopefully this wont put pressure on the heating system or risk getting dirt in the heat exchangers.

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I would start by draining down and seeing what crud comes out of the system. Removing the rads and flushing is more likely to introduce leaks into the system as you break and re-seal the valves. Adding a decent system cleaner may also help when you’ve drained down, but some sort of system filter would be preferable. 

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My experience of having a new boiler fitted to an old CH system was that the power flush (which was mandatory - the boiler warranty was dependent on this having been done) washed masses of crud out of the system, but also highlighted internal corrosion in a couple of radiators, that then developed pinhole leaks at the bottom a few weeks after the system had been flushed.  The leaks were exacerbated by me replacing an old system boiler, fed from an F&E tank that was only around 10 ft above ground floor level, with a combi boiler that is pressurised to around 1.5 bar, so the radiators were not only washed clean of crud, but were now operating at around 4 times the pressure they were seeing before.  I also suspect that the old system had been run without any inhibitor, or that the inhibitor hadn't been changed for many years.

 

A magnaclean or similar in the return to the boiler is, in my view, essential, as it does help trap a lot of the loosened crud that will remain after the flush, and prevent it reaching the boiler heat exchanger.  A lot of boiler problems seem to be caused by crud getting into some of the fine passages in the boiler, and disturbance to the system, like draining it, hose flushing it or power flushing it will end up loosening up crud.  Our system was power flushed for around 2 to 3 hours and a staggering amount of crud came out of it.  When the guys emptied the power flush tank and cleaned the magnetic filter in it there must have been a good bucket full of solid crud that came out, yet we had no symptoms of this, all the radiators were working fine before it was flushed.

 

I've since flushed the system out with a hose, as we had a problem with an odd incompatibility between two different inhibitors, that arose when I topped up the system after changing the pin-holed radiators and fitting a new towel rail.  For some reason the two different inhibitors created a lot of gas in the system and when I drained it what came out was very frothy and milky-looking.  Flushing via the drain off points with a hose seemed to work OK.  After around half an hour I had clear water running out and felt reasonably confident I'd washed the system clean.  Since refilling it with just a single brand of inhibitor we've not had another problem with gas build up.

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I fitted a new boiler for a customer (Gas man did the Gas work and signed it off). But the customer declined a power flush (tight old git) and he called me back (not the gas guy) 2 months later because it stopped working, I got the gas guy to find the problem and a heat exchanger was completely blocked and had to be renewed, customer was furious but Gas guy said I was right telling him a power flush was a good idea, pay up (up front) for the repair or it didn’t get done. He also (like me) recommended a magnaclean.

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On 30/09/2018 at 09:42, Ashley said:

Hi all.

 

My GFCH system must be almost 60 years old and to my knowledge has never been flushed.  have brown water in the header tank and the rads do not heat at the bottom. I have arranged to hire a flushing machine from HSS Hire for next weekend but now starting to worry that flushing the system may expose corrosion in the system which in turn may cause leaks?? What I would like to know is if I am right to  be concerned about this please or should I go ahead with flushing out the system?

 

Many thanks 

 

 

How many rads etc?

 

The last time I looked at a powerflush (admittedly paying someone to do it) the extra to replace the pipes and rads was small enough that I just had the whole thing redone.

 

But that was only a 6 rad system.


Ferdinand

 

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Taking off the rads and blowing them through with cold mains water off the hose pipe is a good idea. I turn them upside down, and give them a few whacks with a hammer and a wooden block. Thats as good / better than a flush IMO, but If theyre over 30 years old, you'd be a heck of a lot better off changing them all to new convectors, and the heat output and reduced boiler temp will be significant. 

A power flush will be expensive, and you'll have to change all the radiator valves at the same time ( thus mitigating against @PeterW's point about causing multiple leak points ). If you change the rads and valves then you can get away without the expensive power flush, so you can then put that money towards the new rads. MrCentralheating online is cheap as chips and do package deals on rads and valves, but do avoid B&Q / Screwfix as the Kudox rads are garbage.

If you have an old boiler I'd not recommend flushing that tbh, but it will be full of crap too. That would be better dispersed by using chemicals, over time. TBH at 60 years its time to spend some money on it as its all probably at the very end of its serviceable and reliable life. A leak could be more expensive than the system having an overhaul ;) 

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Many thanks for the great advice chaps👍

My house is in need of much renovation and I hope to replace the whole system when I do the house up. In the meantime I am still living in the property so just trying to get the current system to work better. 

Edited by Ashley

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12 minutes ago, Ashley said:

Many thanks for the great advice chaps👍

My house is in need of much renovation and I hope to replace the whole system when I do the house up. In the meantime I am still living in the property so just trying to get the current system to work better. 

Run it into the ground and dont waste a single penny on it.

Drain down and throw a couple of these in. That'll stir the crud up and then drain down and refill in a month ( a month of heated use ). 

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