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Boiler Cleaning

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Alan Worland02/05/2012 08:39:55
247 forum posts
21 photos

I am changing some fittings on a copper water tube boiler and when looking inside it looks quite grubby - almost like soot on the main firetube?

I was considering filling with a cleaning solution but wasn't sure what to use.

What is generally recommended?


Brian Baker 102/05/2012 17:36:01
196 forum posts
36 photos

Greetings Alan, I would suggest Citric Acid crystals for a copper boiler, flushed into the boiler with hot water through a safety valve bush, aggitated as much as practical, depending on size, allowed to cool, and well flushed with cold water.

About a heaped teaspoonful for a largest 3.5 in boiler, up to a heaped tablespoon for a large 7 1/4 gauge boiler.

Citric acid is safe to use & will not damage boiler fittings. Some people use drain cleaner etc, but its strong acid content can do damage, as well as being dangerous to use hot.

The residue can be flushed down the drain.

try a home brew shop for bulk supplies.



DMB02/05/2012 20:33:46
1312 forum posts
1 photos

Beware! Somewhere I have read a discussion on various boiler cleaning chemicals where they warn that Sulphuric Acid causes the hard chalky deposits to undergo a chemical change, resulting in the deposit becoming even harder and more difficult to remove and resistant to further use of even very strong solutions of SP. Most toilet/drain cleaners contain either SP or Caustic Soda.

I think it would be very wise to go for the more gentle Citric Acid and see what results.



DMB02/05/2012 20:35:03
1312 forum posts
1 photos

Sorry, I typed SP in error - should have been SA


Alan Worland02/05/2012 20:52:12
247 forum posts
21 photos

Thanks people, I always use citric acid for the kettle but it was the black appearance which was confusing me! However having another look although it appears black (but not sooty like soot) I cant actually see any 'scale' but I can't actually see the area where the main heating goes on so I will give it a workout with the CA

The boiler in question is a marine boiler which measures about 10 inches long by 6 inch diameter and going a bit off topic I would like to paint the ends (which aren't lagged) matt black any recommendations?


Brian Baker 103/05/2012 08:14:57
196 forum posts
36 photos

Hi Alan, what you are seeing is probably a thin layer of copper oxide, a black oxide of copper which forms when the copper in your boiler becomes warm. The same thing happen on the outside with age, the copper turns black.



Ian S C03/05/2012 13:28:35
7468 forum posts
230 photos

To paint the boiler ends, theres paint you can get for painting barbecues, it comes in a rattle can. Nice mat black, until it gets over heated, then it goes gray. Ian S C

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