Central Heating Clean Up?

[GeoffF100]

My micro-bore central heating system is twenty years old. The original boiler was replaced after about ten years. I have had a bit of trouble lately. The ball valve on the header tank had to be replaced, which revealed the header tank to be full of crap. The central heating failed a few days ago, because of an air lock in the pump. When that was fixed, the downstairs radiators were not heating up and the system was very noisy. A new pump was fitted, but that did not change much. Turning the system off for several hours has mostly fixed the problem, which was probably trapped air. A couple of radiators downstairs are cold at the bottom. They are probably full of crap. Perhaps they should be removed and cleaned out. Perhaps the header tank should be cleaned out too. Maybe all the radiators should be cleaned out. Perhaps the system should be power flushed too. What does the team think?

[bungeejumper]

I had all that a few years ago, when the system at Bungee Towers more or less ground to a halt. But it was all fixable by a sufficiently persistent amateur. This was our experience:

Gunk: The downstairs radiators had crudded up because (a) the Fernox in the system was too old, and (b) several of the radiators were themselves rather ancient and had gone black/rusty internally. Up-to-date Fernox and regular bleeding would have prevented all that.

I probably ought to add that all our downstairs radiators are fed by drop pipes from upstairs, so there was nowhere horizontal for the disgusting black residues to migrate to. Instead, they had simply accumulated at the bottoms of the rads until they blocked both the incoming and the return valves, at which point the rads went out of service. I'll guess that yours are just as bad?

It took me several flushes/four months with Sentinel X400 (three doses, I think) to shift the gunk, but it worked fine afterwards and has never given trouble again. You drain the system, put the Sentinel in and refill it, and leave it a month, then drain it again. By the third flush the Guinness in our rads had become palest lager, and we declared the job done.

Warning: The black gunk will ruin any carpet, no questions asked. Take extra precautions. A plumber will probably try and sell you a powerflush (£300-£800), but it isn't always good for your boiler if it's getting a bit ancient. (Can be very hard on the matrix of pipes that do the hard work.)

System noise: We had chronic kettling (like bongo drums) in our system, and we cured it by tipping about a hundred quid's worth of anti-kettling agent into our header tank over a six month period. Far more than the manufacturers would have you believe! And we do have 17 rads, which is not normal. But eventually it worked and our system is now silent.

Note that it always takes a month or so for anti-kettling agents to work - you won't notice much result in the first week, so increase the dose gently and whenever your wallet can afford it. BTW, kettling is doubleplus ungood for your boiler and your pump.

Pump and motorised valve: Both needed changing around this time. No prizes for guessing why, but also do-able by an amateur.

Header tank feed pipe constantly running: We found that the inflow pipe on our header tank was constantly running in the loft, as hot water ran uphill into the overflow pipe and significantly heated the header tank water. (Then it flowed back down into the system in the normal way, so no water was actually lost.) This is nearly always due to iron deposits partially blocking the main 28mm CH pipe, and I had to replace a two foot section of the pipe. Worked perfectly, though, and only took a couple of hours.

Everything AOK now! And the engineer says our boiler (23 year old Rayburn) is the best he's got on his service books.

Any of this ring any bells? Mix and match to suit your own circumstances. If you're allergic to big spanners and occasional swearing, use a plumber.

BJ

[sg31]

That is an excellent response.

[GeoffF100]

Thank you very much for that BJ. My downstairs radiators are also fed from above. The gunk appears to have collected mostly in the two big radiators. The two small ones heat up uniformly.

The noise that I got was a rattling whistle from the pipework. That has gone away now. The plumber who fitted the new pump set the pressure to the maximum (3), I reduced it to the minimum (1), which may have helped, or it may have just been air in the system. Sentinel X400 may well do the job for me too, but getting someone in to drain the system and administer it three times would be expensive. A power flush would probably be cheaper, but a web page that I consulted said that it does not necessarily clear gunk in radiators. The recommendation appears to be to remove them and hose them out.

I live in a soft water area, so I do not expect that limescale is a big problem, but it may be an issue after twenty years. The boiler is an eight year old Worcester Bosch, by the way.

The general drift of your reply is that I ought to do something rather than wait for another failure. I can afford to wait for the summer though. I live in a low cost area, so I may get away with as little as £500, but that may be optimistic.

[bungeejumper]

Sentinel X400 may well do the job for me too, but getting someone in to drain the system and administer it three times would be expensive. A power flush would probably be cheaper, but a web page that I consulted said that it does not necessarily clear gunk in radiators. The recommendation appears to be to remove them and hose them out.

Glad it helped, although not all of it was relevant to you. What I hope I conveyed was that many of these things are do-able for an amateur, even without recourse to a plumber.

Okay, there are three issues there.

The first is that it doesn't take any professional skills to administer X400, except that you have to know how to drain your radiators. All your downstairs rads will (hopefully!) have a drain valve, and you'll be able to drain them with nothing more than a small spanner (pliers if you must ), and a length of hosepipe tubing and several buckets. Hot tip: do the initial drain-down from somewhere like the kitchen rads, where there won't be carpets to ruin. After that you'll just be draining down your selected downstairs rads, one by one.

The second is that there is no obvious need to remove radiators from the wall if you're doing an X400 flush - two or three flushes will loosen and shift whatever crud is there. Incidentally, removing a rad from the wall comes with a definite risk that you'll spill black gunk. As soon as you've taken it off the valves it'll tip slightly sideways and all the gunk will piss out of the ends. Are you sure you want to run that risk?

The third is that your rattling noise might be just a sticking thermostatic valve - try adjusting them a bit to see whether that kills the noise. Or else that you may still have an airlock in your system somewhere. I'd be inclined to give it a week, bleeding the radiators every few days, so as to let the system settle down before you jump to big wallet-sized conclusions.

BJ

[GeoffF100]

The noise has gone. The system is as quiet as a mouse now.

I broke my heel in a climbing accident, and I do not have loft ladder fitted. I could climb up into the loft nonetheless, but I am not keen on doing it by myself. I have done my own plumbing in the past, and am not too bothered about that. My radiators do not appear to have drain valves, except for two, which do happen to be the troublesome ones. As far as cleaning out the radiators is concerned, I was thinking of a professional job. The plumber who fitted the new pump said that he did not do power flushes, but said they cost about £300-£400 locally. I expect to be able to get some cleaning out done too for a budget £500. Job done in a day, hopefully.

My carpets are twenty year old cheap cord, and I am not too bothered about them. Anyone else would replace them. However, if I replace the carpets, perhaps I should patch up the decorations first...

[supremetwo]

The noise has gone. The system is as quiet as a mouse now.

I broke my heel in a climbing accident, and I do not have loft ladder fitted. I could climb up into the loft nonetheless, but I am not keen on doing it by myself. I have done my own plumbing in the past, and am not too bothered about that. My radiators do not appear to have drain valves, except for two, which do happen to be the troublesome ones. As far as cleaning out the radiators is concerned, I was thinking of a professional job. The plumber who fitted the new pump said that he did not do power flushes, but said they cost about £300-£400 locally. I expect to be able to get some cleaning out done too for a budget £500. Job done in a day, hopefully.

My carpets are twenty year old cheap cord, and I am not too bothered about them. Anyone else would replace them. However, if I replace the carpets, perhaps I should patch up the decorations first...

One problem with a power flush - it could push sludge into the boiler so if it is just those two radiators, they should be removed and thoroughly-cleaned first.

Presume there is no filter on the existing system?
Here is an example:-
https://boilerfans.co.uk/boiler-m8-ulti ... -22mm.html

[GeoffF100]

One problem with a power flush - it could push sludge into the boiler so if it is just those two radiators, they should be removed and thoroughly-cleaned first.

Presume there is no filter on the existing system?
Here is an example:-
https://boilerfans.co.uk/boiler-m8-ulti ... -22mm.html

Yes, I would want the the header tank and the two troublesome radiators cleaned out before doing a power flush. Perhaps I should have all the radiators cleaned out first, or at least all the downstairs ones. Perhaps the part of the pipe from the header tank where sludge builds up should be replaced first too.

Yes, there is filter to protect the boiler. I had that fitted when the replacement boiler was fitted.

[supremetwo]

One problem with a power flush - it could push sludge into the boiler so if it is just those two radiators, they should be removed and thoroughly-cleaned first.

Presume there is no filter on the existing system?
Here is an example:-
https://boilerfans.co.uk/boiler-m8-ulti ... -22mm.html

Yes, I would want the the header tank and the two troublesome radiators cleaned out before doing a power flush. Perhaps I should have all the radiators cleaned out first, or at least all the downstairs ones. Perhaps the part of the pipe from the header tank where sludge builds up should be replaced first too.

Yes, there is filter to protect the boiler. I had that fitted when the replacement boiler was fitted.

Did your plumber clean that when he fitted the replacement pump?

[GeoffF100]

I did not know that the filter needed cleaning. The plumber who fitted it did several annual services and did not mention it. Too much like hard work probably. I will add that to the list.

I appear to have two jobs. Firstly, clean out the troublesome radiators, tank and filter + boiler inspection + perhaps other items. Secondly, a power flush.

[sg31]

I did not know that the filter needed cleaning. The plumber who fitted it did several annual services and did not mention it. Too much like hard work probably. I will add that to the list.

I appear to have two jobs. Firstly, clean out the troublesome radiators, tank and filter + boiler inspection + perhaps other items. Secondly, a power flush.

See if you can find the make of filter. I've had several on different properties going back to when the magnetic ones first came out and they were all designed for easy cleaning.

Usually there is a valve either side which you close. The there is a chamber which you unscrew. Clean the magnet, replace the chamber, open valves, open a bleed screw until water appears, close bleed screw and then top up system if needed.

It takes almost as long to write as to do the job. If you know the make someone on here might now the correct procedure.

Personally I'd be tempted to clean out the downstairs rads that are causing the problem and leave it at that provided you can clear the filter regularly. Those downstairs rads are acting as a sump, catching all the crud.

[AsleepInYorkshire]

My micro-bore central heating system is twenty years old. The original boiler was replaced after about ten years. I have had a bit of trouble lately. The ball valve on the header tank had to be replaced, which revealed the header tank to be full of crap. The central heating failed a few days ago, because of an air lock in the pump. When that was fixed, the downstairs radiators were not heating up and the system was very noisy. A new pump was fitted, but that did not change much. Turning the system off for several hours has mostly fixed the problem, which was probably trapped air. A couple of radiators downstairs are cold at the bottom. They are probably full of crap. Perhaps they should be removed and cleaned out. Perhaps the header tank should be cleaned out too. Maybe all the radiators should be cleaned out. Perhaps the system should be power flushed too. What does the team think?

Is it micro-bore or small bore?

If I recall correctly power flushing on "micro-bore" can create more problems than it resolves. I'm not a plumber but would suggest you identify the size of the pipework [correctly] first and then search for the [correct] maintenance regime. Cold radiators at the bottom sounds like trapped air. I can't understand how "sludge" [crap] would gather in a system in the amounts you infer. However, and as stated I'm not a plumber and have very limited knowledge of this subject.

AiYn'U

[Itsallaguess]

See if you can find the make of filter. I've had several on different properties going back to when the magnetic ones first came out and they were all designed for easy cleaning.

Usually there is a valve either side which you close. The there is a chamber which you unscrew. Clean the magnet, replace the chamber, open valves, open a bleed screw until water appears, close bleed screw and then top up system if needed.

It's also worth mentioning that the process of cleaning a central heating filter is often also a very good opportunity to top the system up with inhibitor, replacing the dirty system-water that has been discarded with new inhibitor fluid suitable for the particular heating system being worked on.....

Cheers,

Itsallaguess

[GeoffF100]

I have been out in the garage and had a look. There does not appear to be a filter. If there was one, I would expect it to be above the boiler where the pipework goes under the floor of the upstairs rooms. My memory did not serve me well after eight years. It seems that magnetic filters are not all they are cracked up to be:

https://www.telegraph.co.uk/lifestyle/i ... -idea.html

Perhaps I should get a kit to test the inhibitor level, or do the nail rust test:

https://www.plumbersforums.net/threads/ ... or.92095/#

The plumber noticed that the two big downstairs radiators were cold at the bottom, and suggested that that was caused by sludge in the radiator. This website confirms that diagnosis:

https://www.onlyradiators.co.uk/blog/ra ... -at-bottom

MIcrobore can be power flushed safely, but it takes longer:

https://www.phamnews.co.uk/debunking-th ... rflushing/

The plumber (who teaches at the local college) seemed to think it might be worthwhile.

I think my best plan here (apart from further consultation) is to get the downstairs radiators cleaned out, and the cruddy water bailed out of the header tank. (How did it get like that is a good question.) That should not do any harm and should not be too expensive. If that fixes the problem, I probably do not have to do anything more.

[sg31]

I would always fit a magnetic filter to a system if I'm having any work done on it. Radiators are steel and by design have a large surface area so renoving any ferrous gunk from the system has to be a good thing. They aren't very expensive and I prefer to have them as a back up to inhibitor.

Each to their own and I'm sure others will have different views.

[bungeejumper]

I have been out in the garage and had a look. There does not appear to be a filter. If there was one, I would expect it to be above the boiler where the pipework goes under the floor of the upstairs rooms.

Could be anywhere on the circuit, actually - they're often hidden away in the airing cupboard. But yes, I gather that the best results are obtained if they're located between the boiler and the last radiator on the system.

BJ

[sg31]

I have been out in the garage and had a look. There does not appear to be a filter. If there was one, I would expect it to be above the boiler where the pipework goes under the floor of the upstairs rooms.

Could be anywhere on the circuit, actually - they're often hidden away in the airing cupboard. But yes, I gather that the best results are obtained if they're located between the boiler and the last radiator on the system.

BJ

Mine have always been next to the boiler on the return pipe. Obviously if there isn't room near the boiler one would need to try elsewhere.

[GeoffF100]

My main problem appears to be air getting into the pump. The old pump was probably OK. The plumber is going to try feeding water into the system at mains pressure from a downstairs radiator to blow air out of the system. He suggests that converting my vented system into a pressurised system will fix this problem. That should stop air and muck getting into the system. One of my friends had the same problem, and converting to a pressurised system fixed it.

As far a cleaning out the system is concerned, the plumber thinks that he can find someone to do a power flush for a reasonable price. He should be round in the next week or so. In the meantime, I am getting enough heat out of the system to be reasonably comfortable, and I am getting used to the horrible noise from the pump.

[bungeejumper]

My main problem appears to be air getting into the pump. The old pump was probably OK.

That's odd, I thought pumps were self-bleeding these days? My Grundfos Alpha 2L certainly is, and it's on an open vented system like yours. (Cracking good pump, BTW, and not expensive if you shop around.)

Somebody else has had a problem with air getting into even an Alpha 2 pump, and the discussion might be of interest. https://www.diynot.com/diy/threads/air- ... -2.474232/ . One of the posters has asked whether the pump was on a vertical or a horizontal pipe? (Can be set up for either.) And yes, it's theoretically possible to install a pump in the wrong direction entirely! (Slow and erratic thermostatic control, cos the stats are now on the wrong ends of the radiators, and it doesn't do your boiler any favours either.) If my new pump were taking in air, I think I'd be asking myself some serious questions about the plumber.

For the moment, though, make sure the inhibitor is up to date, and bleed the system every few days for a week or two, because they do sometimes get pockets of air left in them after draining. You can sometimes blast airlocks out of cold areas by turning off other radiators so as to concentrate the flow through the problem areas. One of our rads is always cold for two days after a full drain-down, but it rectifies itself. Good luck.

BJ

[GeoffF100]

The plumber fitted the boiler and pump, and the system has been running well for eight years. He also successfully fitted a combi system for my neighbour who is a retired plumber, and recommend him. He teaches at the local college. I should be OK there.