Cleaning out cast iron boiler

[camerart]

I've got a cast iron boiler that bangs and pops when heating up. I've flushed out the whole system a couple of times before (Asked questions on DIYNOT before regarding this) so the rads and pipework are ok.

I want to disconnect all of the pipework and circulate Hydrochloric acid only round the boiler. I won't be able to easily disconnect the copper 28mm hot water circulation pipes and want to know if these will be eaten by the acid also.

Any advice welcome.

Camerart.

 

[Agile]

Whilst HCl is cheaper it also attacks copper which is not ideal.

If its used warm then sulphonic acid is probably safer and could be better if its calcium compounds causing the problem. Its sold as Fernox DS3.

Much of Dorset has fairly hard water so that's quite possible.

Tony

 

[camerart]

Whilst HCl is cheaper it also attacks copper which is not ideal.

If its used warm then sulphonic acid is probably safer and could be better if its calcium compounds causing the problem. Its sold as Fernox DS3.

Much of Dorset has fairly hard water so that's quite possible.

Tony

Ok Tony, thanks. I'll use DS3.

 

[Agile]

It has little action below about 80 C and is not very soluble except in almost boiling water.

Tony

 

[camerart]

It has little action below about 80 C and is not very soluble except in almost boiling water.

Tony

First/ I've tried to find out if copper is corroded by Hydrochloric acid, and perhaps it isn't?

Second/ I presume you are talking about DS3? Should I heat it up first when mixing, or turn the boiler on while circulating?

Camerart

 

[Agile]

HCl is not directly seriously attacking the copper but with iron it can form ferric chloride which will attack the copper.

The DS3 needs to be virtually boiled to encourage it to dissolve.

When in the boiler the boiler needs to be fired at max temp for it to have much action.

I do that with all rads off and just the HW heating coil taking the flow.

Tony

 

[Agile]

The DS3 is good for calcium compounds but not so good for iron based sludge.

Citric acid is good for iron and copper based sludge. That's mostly what is in Fernox DS40 but pure citric acid is better if you can get it.

You have not said what boiler model you have so I cannot make many guesses.

Tony

 

[camerart]

The DS3 is good for calcium compounds but not so good for iron based sludge.

Citric acid is good for iron and copper based sludge. That's mostly what is in Fernox DS40 but pure citric acid is better if you can get it.

You have not said what boiler model you have so I cannot make many guesses.

Tony

Thanks Tony.

The boiler is: Myson house warmer 45 back boiler.

I planned to disconnect the heating pipe work from boiler and pump the acid round the boiler by an external pump, but it seems that you leave it all connected, and just circulate the hot water. The boiler uses self circulation for hot water, which works fine. I just didn't want to damage the copper.

So what complete process do you suggest?

Cheers, Camerart.

 

[camerart]

Does anyone know if the hot water heat exchange and the central heating heat exchange are separate in an old cast iron boiler? (Myson house warmer 45 back boiler)

Cheers, Camerart.

 

[Terrywookfit]

Does anyone know if the hot water heat exchange and the central heating heat exchange are separate in an old cast iron boiler? (Myson house warmer 45 back boiler)

Cheers, Camerart.

No it's all one assembly.

 

[45yearsagasman]

If your system water is clean then forget trying to "clean" a cast heat exchanger. Put some Fernox System Silencer in the system and it should quieten it down considerably. 28mm pipes suggest a gravity hot water system to me, and after several years the boiler will become noisy.

 

[camerart]

Thanks Terrywookfit, and 45yearsagasman, I'm just figuring out what to do.

I've flushed out the system a few times now, and even though I think most of the sludge etc is out, and everything gets hot, the boiler has always knocked a bit. You are the experts, but I keep thinking that an acid clean will help especially if calcium has got built up in the corners. After that I can always add Fernox later if it's still noisy. What do you think?

Cheers, Camerart.

 

[robin7]

My Potterton Netaheat Electronic 16-22 boiler (which also has a cast iron heat exchanger) was kettling seriously - very loud banging and knocking which resonated through the pipework and could be heard all over the house. I used Fernox DS40, closing off all the rads and therefore circulating through just the boiler and cylinder coil - and the boiler now runs almost silently. I was very pleased with the result!

 

[camerart]

My Potterton Netaheat Electronic 16-22 boiler (which also has a cast iron heat exchanger) was kettling seriously - very loud banging and knocking which resonated through the pipework and could be heard all over the house. I used Fernox DS40, closing off all the rads and therefore circulating through just the boiler and cylinder coil - and the boiler now runs almost silently. I was very pleased with the result!

Thanks Robin7,

That sounds good. Was it done recently? I was wondering if this is a long term solution. I'm reluctant to get rid of my old boiler, because it works well apart from the noise.

Cheers.Camerart.

 

[robin7]

The kettling in our boiler became progressively worse over some years, and last year I decided to try the DS40. Time will tell if it's a long-term solution - I imagine that the scale build-up will return over time, in which case I'll use DS40 again. Good luck with yours!