Sludge in Central Heating System

[RedHP]

Hi all,

I hope you can provide me with some advice please !

We have encoutered sludge in our system ever since we moved into the property in 2005. It was built in 2000, so is relatively new. We are currently running on a standard boiler (not combi etc)
I have had 7/8 different plumbers come out and try different things, from flushing out the system, powerflushing, adding sludge remover etc, but the sludge keeps returning. One plumber actually removed most rads and flushed them out with a hosepipe and also the small tank in our loft (which was full of sludge too), though again this has not solved our problem.
Another plumber suggested that we require an immersion pipe (?), but then found out from colleagues that this wasn't the case.

We are certainly getting oxygen into the system somewhere, hence the sludge.

All plumbers have suggested that the only certain remedy would be to have a closed system fitted, or in other words a combi boiler.

Is this the only solution, as our current boiler itself is fine and I don't really want to replace it? Also, what if the sludge reappeared in the new system (if this is possible)?

Any advice/assistance would be greatly appreciated, as I am at the end of my teather !!

Many thanks

Red

 

[transam]

closed or sealed system ! most boiler's can be installed on a closed or sealed system you do not need a combi in order to do this !!! constant sludge build up ?? a leak or your system is pumping over into the exp tank/cistern ?? do you have trv's on all rad's are they all on low or off ?
or ststem is piped incorrectly cold feed & vent configeration ?

 

[mysteryman]

It is probably pumping over from the vent pipe into the feed and expansion tank, or it may be sucking air down the vent pipe. This would mean that the radiators need frequent venting - always a bad sign. Take a look with the pump and boiler operating. If the water is an angry red rust colour, then it is almost certainly pumping over. You must get it stopped.

You should call in a competent central heating installer. This process is damaging your heating system.

 

[petit_pablo]

Do you have plastic or copper pipes on the system?

We have estates round here that were piped in non-barrier plastic. These pipes were allowing air into the system and causing sludge to build up.

 

[RedHP]

Thanks for your replies so far:

sam - All rads are off at the moment, but they have been high during the winter (though this had no effect as rads remained fairly cold anyway)

mystery - Its not a red rust colour, but a brown/black colour with lumps of sludge

pablo - They are those grey plastic pipes used with most new houses.

Apologies but I'm not very clued up about plumbing so may not be able to answer technical questions.
So you guys think that a combi might not neccesarily sort the issue?

Red

 

[RedHP]

Bump

Anyone please, before I potentially waste more cash (which is very tight at the moment)?

Thanks again in advance

Red

 

[MIGEM]

How many times has the system been flushed with a chemical flushing unit, with all valves open initially, the pipe work flushed, the radiators flushed individually in both directions, the vent and tank outlet connected together, the F&E tank cleaned, the motorised valves manually opened, and flushed from the pump head with the boiler running, and for how long?

If the radiators are corroded internally, a power flush and chemicals will not cure or stop what has already occured. If too much of the inside of the radiators has broken down and been flushed away, small holes can be exposed which may allow leaks and possibly air to be sucked in, especially around seams and rad valves. Also if you have a leak under the ground floor boards, the F&E tank will be introducing airated water. One further problem that can be later discovered, when you change from an open vented system to a pressurised system, is that you discover leaks, so have the system pressure tested first, either with air or water, before you change boilers. A calm days work for an installer, should cure your problem if he is methodical and understands what he is doing.

 

[Agile]

Will your boiler allow operation on a sealed pressurised system?

One of those plumbers should have told you that!

Was one of them called Namsag ( or Phill ) ?

Tony

 

[Agile]

Will your boiler allow operation on a sealed pressurised system?

One of those plumbers should have told you that!

Was one of them called Namsag ( or Phill ) ?

Tony

 

[RedHP]

The system has been flushed with chemicals, 3 times in 2 years. Each system flush (with valves open and also shut) were 2 hours a piece.
After that the rads have been taken off and flushed through individually.
Twice the chemicals have gone into rads, and on one occassion into the tank in the loft.
Over the past 4/5 years we have had about 7/8 different plumbers (all combi/gas safe qual) test our system and suggest different actions, all to no avail.
A couple of them has suggested that there may be a leak, with air getting into the system, hence all the sludge. They also suggested that some rads may be corroded internally and that I may need to rip out the entire system, and replace (ouch, that would hurt in monetary terms!)

So you suggest I pressure test the system to detect whether there are any leaks. If there are, what are my options, similarly to what if there are no leaks?

Surprisingly from the responses I have received here, they have ALL suggested that I replace with a close system, i.e. combi boiler.

It seems that the professional plumbers/heating experts I have encountered do not have as much knowledge/expertise as many of you.

Red

 

[Alfredo]

Like others say..MOST boilers on open systems can be converted to closed systems. What make/model/year of boiler is it? If the manufacturer says yes, its not an unduly expensive exercise, if they say no, then you can't do it.

Also as others say, if you do go to a closed pressurised system it will expose any weakness in joints and/or rads that an open system would tolerate, so be prepared to be leak vigilant.

What speed is the pump on? If its on high speed that can make air problems worse in some cases, but I'd go with the pumping over scenario if I were a betting man. That the only way to introduce big volumes of air that would cause such rapid corrosion.

Alfredo

 

[Happyplumber]

Can you please tell us the make and model of your boiler,a pressurised or closed system doesn't necessarily have to be combination boiler.

Alot of systems can be converted from open vent ,as long the boiler manufacturer stipulates this is possible in their installation manual.


Thats why i would like to know this extra bit of information

 

[Boilerman2]

Sealing a system is often the repair of choice for a system that pumps over

 

[vulcancontinental]

As you say you have plastic piping I'd look at the cut end of a piece of pipe and see whether there is a metal 'rim' within the wall thickness. You could look at the end of the open vent above the feed tank. Non-barrier pipe will ingress air throughout the system that will give you the problems you describe which do seem extreme.

Otherwise take a photo of the pipework above the pump so we can see it.

I personally do not like pressurising older systems if it can be avoided, after all the sludge you describe is of course what's left of the metal that once formed part of the skin of the radiator.

I've always found a separate 22mm cold feed with a 22mm expansion pipe sufficient to overcome most problems I've been confronted with connected in the normal configuration. If the boiler manufacturer will allow it a 22mm close coupled arrangement works also.

How high is the bottom of the feed tank above the pump (and also the boiler)?

 

[Happyplumber]

This system was installed in 2000!