Brown sludge in header tank. Boiler cuts out after 5 minutes

Jane57 · 14 Jan 2008

Wondered if anybody has any ldeas that may help solving our heating problem.

When we got back from a month away last week the radiators downstairs were all cold but upstairs was very hot. We had left our thermostate which is downstairs in the hall set on 15 degrees and the timer on constant to keep the house aired out. Our plumber first thought it was a blockage as he tested the pump and it was still spinning although rather noisy. He bought something to flush the system but this made it worse and the boiler cut out so he said he would drain and flush the system the next day.

After draining and flushing it was the same so he thought the pump should be replaced as it was 18 years old and noisy. I purchased a new Grundfos Alpha plus pump whiich was fitted yesterday but still no improvement and the boiler cuts out after five minutes and nothing even starts to heat up!

Also the header tank in the loft was full of brown sludge that was also weighing down the ballcock which has been cleaned now but I am wondering what caused it and if some has got into the pipework. We did put a hose in the header tank & back flush it and it appeared to drain ok.

He says that the radiators all filled and there is no air in them so either there is air trapped in the boiler or the thermostats on the boiler have failed. I am not convinced this is the problem and any suggestions would be welcome please!

easyflow · 14 Jan 2008

Jane

If your plumber is sure that there are no air locks within the heating system and a motorised valve is not preventing the heating to operate.
Chances are theres a blockage either sludge or debri.
I would first try a power flush, if this dosnt clear the problem I think you may be faced with cutting 22mm pipe sections from the system.
These hard to remove blockages occur in elbow bends and Ts.

Jane57 · 14 Jan 2008

Thanks for reply.

I have tested the pipework below the pump with a magnet & it is very magnitized below the pump & on the pipe & bend that go across and around a bend.

The system was washed down and flushed through and my plummer says there is no air locks in the pipework or radiators but says there could be some in the boiler which he does not know how to get out if there is as I have no manual on the old boiler and there is no obvious way.

Slugbabydotcom · 14 Jan 2008

Edit

Deleted
I never read the post properly

easyflow · 14 Jan 2008

Well if your plumber thinks theres air trapped in boiler do this.

Attach hose to boiler drain cock (securely), and open drain cock, turn on mains tap slowly,
It may be wise to use a check valve to stop back flow.
This will back fill the heating system and in turn get rid of any air in boiler section(s).
Somtimes a manual vent is fitted onto the flow or return pipes if a system suffers from air locks (check for this first)
But I still think this problem is a debri blockage.

The Baker · 14 Jan 2008

Jane57 please allow me to congratulate you on your lateral thinking.

Your use of a magnet is an excelent idea and one which I will be adding to my box of fault finding tricks.

Thanks,

Tim

twgas · 14 Jan 2008

magnetic copper pipes and sludge in f&e tank=system at least partially blocked if not completely in places, this will cause poor circulation and the reduction in heat to some rads, downstairs in your case because its easier for the water to just circulate round upstairs rads
add some sentinel X400 and leave for a few weeks before thoroughly fushing with clean water. It may be worth turnig off upstairs rads so that downstair circuit gets cleaned as well.

once flushed out refill with clean water and add sentinel X100.

Jane57 · 14 Jan 2008

The Baker

I found this tip when I Googled the problem so cannot take credit for the idea!

Twgas

The first thing we tried was adding Sentinel X400 & we bought the X100 to add later but soon after adding the X400 the boiler just cuts out every 5 minutes so we cannot circulate it.

Jane57 · 14 Jan 2008

PS

Boiler engineer just checked the boiler & he says it got no air blockage & the thermostat is fine so it is a blockage.

I guess its a Powerflush we will have to go with. Not sure if everyone charges £500. Might try a few more quotes!

easyflow · 14 Jan 2008

You can hire a power flush for about £70 to £80.

bengasman · 14 Jan 2008

powerflush with fx2 should solve the problem. this is acid, so i would not recommend this as a diy adventure

The Baker · 14 Jan 2008

Your system may have been pumping over for years.

This could have been adding oxygen to the system water which I belive would show as brown slude in the header tank.

Depending on which boiler and what type of heat exchanger it has is may be knacked.

Just a thought, but £500 would go a long way towards having the rads removed and flushed out with a hose pipe, and a new boiler with a magnearclean, and in your case an inline strainer fitted in the return pipe work, may be a better long term solution.

Good luck,

Tim

Jane57 · 14 Jan 2008

Re last post from The Baker.

Thats what I was thinking. Our boiler is a 1985 Myson Valaire oil fired.

We concidered getting a new one a couple of years ago before the new regs. came in but one of our quoters said there wasn't must to go wrong on them and that it could keep on going for another 10 years which is about the life of new boilers these days so we didn't do it.

We did have a new pump, new thermostat and the system flushed and inhibitor added about 4/5 years ago.

We have quite a large system though with 16 radiators of which 7 are doubles so its going to cost a lot to replace.

Slugbabydotcom · 15 Jan 2008

The Baker said:
Your system may have been pumping over for years.

This could have been adding oxygen to the system water which I believe would show as brown sludge in the header tank.

This was along the lines of where I was going with the post I deleted earlier. I made a mistake and didn't have time to sort it out.

Do a post mortem on the old pump. It is possible that the pump itself was the source of the air ingress. Old grundfoss pumps seem to do it now and then. The last time I saw it was on a large 22 rad system and the pump was a commercial sized one to allow for the extra load. In this case the impeller had snapped off from the armature.
The way to tell is if the inlet is black and the outlet is rusty red. If the old pump was where the air was getting in then just after it is the part of the system most prone to blockage as thats where it reacted with the air. Any Iron fittings just after the pump are suspect blockage hot spots.[Dissimilar metals]

Jane57 · 15 Jan 2008

Thanks Slugbabydotcom & The Baker for the last two posts which seem to address the problem

It looks as if it is a severe blockage below the pump. We drained the system and took off one piece of the pipework today and fushed again but the boiler still locked out after 10 minutes so we didn't get it all. Not much more we can get to without having up the recently fitted carpets and tongued & grooved floorboards!

Looks as if I will have to go with Powerflushing as the problem is mainly in the pipework not the rads and even if we need a new boiler most companies require an old system to be flushed.

I guess there could be quite a lot of muck throughout the whole system and its not the weather for taking off 16 radiators and flushing them in the garden and this would not help clearing debris in the pipework.

Thanks to all who posted.

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Brown sludge in header tank. Boiler cuts out after 5 minutes

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