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Radiator partially hot

When a radiator is hot and the centre bottom section is cold what is the problem? There is no air in the radiator. TIA

Reply to
timegoesby
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It's full of sludge - which is a by-product of corrosion. This is caused by having insufficient inhibitor in the system and/or by air entering the system.

You need to drain and remove it, take it outside and give it a really good wash out with a hosepipe. [You probably need to do the others while you're at it]

The flush the whole system with all the rads in place, to clean the pipes and boiler, and add the requisite amount of inhibitor.

If it's a vented system, make sure it isn't "pumping over" - which would cause air to get into the system, increasing the rate of corrosion.

[Be very careful how you drain and remove the rads - black sludge will re-style your carpets for ever if spilled on them!]
Reply to
Set Square

Sludge.

It collects in a triangular pile in the bottom of some or all of the radiators.

It can be avoided by the use of inhibitor in the system.

At this stage of disease, using chemicals added and run in the system for a while is not going to cure the problem any time soon. Either you can rent a power flush machine and try and flush the system through with it, or drain and flush the system and take each radiator outside for a thorough pressure wash through.

Inspect them carefully, because if there is much sludge, they could be on their way out.

Take great care because sludge and rusty water are indellible dyes.

A good solution (after draining) is to put plastic sheet and plenty of newspaper under a radiator, then undo the unions and drain the dregs into a container at each end (cat litter trays from the supermarket do for this) and then tip the radiator carefully. have some plastic bags and rubber bands to attach to the tails while you take them outside.

At each radiator position flush from the pipework by adding some more water to the system and run it clear.

Reassemble the system and refill, adding some chemical flushing agent. Run this hot for the recommended time (could be a day or a week) and then flush with fresh water. Refill adding inhibitor.....

Replace inhibitor every three years.

.andy

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Reply to
Andy Hall

Just to moderate Andy's warning slightly, I spilt some black gunge from a radiator on a carpet last year whilst undertaking the flushing/desludging steps described.

I found that a very strong concentration of 1001 carpet cleaner while the stain was fresh has effectively removed the stain from the carpet. It was quite a light coloured carpet with inbuilt bleachability IYSWIM (I think they dye the fibres before they are combined into threads or whatever) but a small amount of spillage might not be the end of the world if the conditions are right, IME.

Of course, take whatever precautions you can but if the worst happens you might not be as badly off as you think.

HTH

Neil

Reply to
Neil Jones

Thanks. I thought it might be sludge. Is it possible to put in a larger dose of Sentinel sludge remover and leave it for around a month after heating starts full time which will be in a week or two. Will this soften up the sludge and then it is a matter of just draining out and flushing a few times?

I would rather use chemicals and wait than remove rads. The carpets are cream and nearly new and the last thing I would want to do is stain them in any way. Removing rads and power flushing them through sounds too drastic in this day and age. Chemicals must remove this stuff or does it? Sentinel sludge remover sounds suspect if rads have to be removed to remove sludge. Is this stuff a con?

Reply to
timegoesby

I have to admit to not having ever flushed my own system (but I *have* experienced black sludge on carpets when draining individual radiators for decorating!) so my remarks are based mainly on what I have read here.

The general concensus seems to be that if a system is badly sludged, chemicals don't work - and that it's case either of removing the rads to wash them out, or of having the system power flushed (for which you can apparently hire the equipment in order to DIY).

Reply to
Set Square

Please see my post on this.

I think that it is unlikely that with this level of sludging that you will remove it with chemicals pumped round just with the heating pump.

It's a matter of degree. If it were a little in the bottom then possibly. If you have enough sludge that you can feel that the radiator is cold at the bottom then there is a lot.

The method of removing the radiators is the best, but if you don't want to do that or remove radiators then you can rent a power flushing machine. These connect at two points on the system and chemicals are pumped round under pressure.

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what's involved.

Alternatively there are companies that will do this for you. Note in the datasheet for the pump above that the manufacturer talks about high profits. They aren't kidding. Charges can be £500-800 for this.

.andy

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Reply to
Andy Hall

I can vouch, sludge causes your problem and the chemical cleaners are not guaranteed to work.

In my last house I had triangular cold patches in all the middle of the radiators when I first moved in, so I first tried just flushing with water ie drain down, fill system, pump a bit , drain down etc. Well water never went clear and radiators still had cold patches. Tried a cleaner for a week, the smaller radiators were fine, but still cold patches on larger ones. Eventually bit the bullet, took all radiators off, flushed using hose pipe (I had a handy man hole I could flush into without staining garden paths etc etc). Put all back filled system (checked for leaks), pumped, emptied a few times, added Fernox inhibitor and system was fine for years.

Reply to
Ian Middleton

When there is a lot of sludge not only has inhibitor not been used but there is a very great chance that the existing installation has one or more faults which are increasing aeration/air ingress.

Reply to
Ed Sirett

Thanks. The large rads. Did the cold triangles diminish at the end of the week using chemicals? If they did then the chemicals were working and my feeling is that you may have not left it for long enough.

If I did a double dose of sludge remover and left it in for 2 to 3 weeks it may get rid of the triangles, and sluge. Do you think it is worth double dosing, running very hot and leaving for 2 to 3 weeks? My current view is to try this and see. If there are triangles of cold, meaning it never fully worked, then take the rads off. What sludge remover did you use? I have found out, yesterday, that Fernox requires about three flushes to remove it while Sentinel only requires one. Is Fernox prone to leaving leaks?

The system was sucking in air. This was rectified by lowering the pump speed. Would it be worth it if I changed some of the pipe and have the pump on full? The extra pressure, working with chemicals, may dislodge the sludge

Or is it worth turning off all rads and leaving one open with the pump on full for a 24 spell at a time? Then all pressure is going through that rad only. That must make a difference.

Reply to
timegoesby

If it is cold just after start up, then this is just showing the way the water flows in the rad - in bottom left (say) - rises as lighter than cold water, then plunges to bottom right (say) to exit.

If it is permanently cold there then its clogged with sludge, which tends to accumulate in the slow moving bit of the rad (see previous paragraph)

Andrew Mawson, Bromley, Kent, UK

Reply to
Andrew Mawson

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