Cleaning secondary heat exchanger for domestic hot water

What's the best stuff to clean a secondary heat exchanger?
Periodically, mine needs a degunge and I use normal bog standard descaler such as a kettle descaler.
It does work, but I was wondering if there is anything better which is safe to use?
Steve...........
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The local heating guy told me to pour sulfuric acid (the drain cleaning stuff) down the CH flow or return connection until it come up the other side and then leave it overnight before rinsing all the crap out with lots of water, I've used citric acid in the hot water side. Make sure its stainless steel though!
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Furnox DS-3 is the stuff to use. It's Sulphamic (not Sulphuric) Acid, plus an indicator dye to tell you when it's used up, plus a scent so you don't drink it. You used to be able to buy it in B&Q, and builders merchants used to stock it, but the larger tubs have got harder to find, so I order it from BES.
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Andrew Gabriel
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On 19 July, 18:25, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

Interesting, will there be any harm in using the sulphuric acid though? I have already got a bottle and just about to pour it in the heat exchanger.
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That's really a question for the manufacturer. Depends what the heat exchanger is made from. It's probably ok with stainless steel. Heated sulphuric acid can corrode some stainless steels and the walls tend to be very thin, but you aren't going to have it in contact for long. If it's not stainless steel, then you'll have to say what it is.
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Andrew Gabriel
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On 20 July, 14:20, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

It's a stainless steel from a Vaillant turboMAX
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In message

Phosphoric acid
http://www.kamco.co.uk/FX2.htm
or sulphamic acid
http://www.globalspec.com/industrial-directory/sulfamic_acid_cleaner
under one of the proprietry names like Fernox DS3
--
geoff

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On Mon, 19 Jul 2010 07:07:08 -0700, dog-man wrote:

For descaling the DHW side I use Kilrock-K ("inhibited formic acid" IIRC) - which is also sold in diddy little bottles as kettle descaler. Then fit a proper scale inhibitor (http://yaph.co.uk/limescale /) to stop it happening again.
If it's blocked on the primary side then a powerflushing machine with a PHE adaptor seems to do the trick temporarily but you'll need to address the cause of the problem which probably means powerflushing the whole primary system and/or fitting a Magnaclean/Boiler Buddy/equivalent filter to the primary circuit to remove/catch crap circulating around it.
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John Stumbles -- http://yaph.co.uk

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