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wavel · Joined: 08 Mar 2003 Posts: 1 Location: Surrey

I've just had a new condensing boiler installed (Potterton Promax if you're interested) and at the same time had my system converted from vented to sealed. The plumber did not flush the system or add any inhibitor. He said there was no point in flushing it and you don't need inhibitor in sealed systems because you're not adding any fresh water. It didn't sound right to me but perhaps someone could confirm whether me or the plumber is correct.

Thanks
Ian.

ChrisR · Posted: Sun Mar 09, 2003 12:30 am Post subject:

Hopefully your plumber left the manufacturer's Installation and Maintenance instructions with you. He is required to do so by law.

Not that he has much respect for the instructions. Or regulations, or British Standards, or you.
The instructions have about eight paragraphs stipulating what measures need to be taken on water treatment. It starts:-
"All recirculatory water systems will be subject to corrosion unless an appropriate water treatment is applied"
Part way through it says, in a box, bold :-
"Failure to flush and add inhibitor to the system will invalidate the appliance warranty"
One of the British Standard Codes of Practice referred to is BS7593, which requires chemical cleaning, use of especially provided full flow flushing points (which you will not have) and further measures.
A machine has to be used to do the flushing; it is not just a fill and empty.

Experience shows that sealed systems have no trouble at all in building up considerable quantities of corrosion products if inhibitor is not used. Dissolved oxygen plays a part, and it is true that continuous introduction of fresh water is undesirable. That's a red herring - the water in the system is static and one filling will not contain enough to do much damage - or indeed NO damage if an inhibitor is used. Most of the dissolved oxygen is removed in the first heating cycle. However, all water has an equilibrium concentration of H+ and OH- ions dissolved in it, which react with iron and other system materials. When some oxygen ions are taken out of solution by the rusting process, the equilibrium concentration is restored, by splitting water molecules: H2O. Hydrogen is produced (which needs to be "bled" from the radiators) and rusting continues. More aggressive are the flux residues which are left in the system after soldering. You will have just had some added by your installer, to whatever unknown amounts that were already there.

The waterways in modern boilers are far smaller than in the cast iron monsters of old. Blockages happen very frequently. The boiler will become noisy and inefficient, and sensors can become clogged. Your boiler performance will be seriously compromised by your plumber's combination of laziness, ignorance and greed. Your boiler has Aluminium in it, which makes your system more vulnerable. Problems typically show up within a few years, perhaps 2 - 5, by which time your plumber will accept no blame.

Further, every boiler installed now has a "Benchmark" Installation, Commissioning and Service Record Log Book. This must be left with the customer, and be filled in with the Corgi registration number and ID card serial number of the installer as well as the cleaning chemicals/procedure used and the Inhibitor added.

I suggest you start by calling Potterton (08706 096 096) to get the Instructions and benchmark certificate - which you probably don't have.
You might also like to talk to their technical people on 08706 049049 (though you will have to hold for a while).

After that, there may be no obvious next step. Plumbers in this country do not have to be qualified or registered. Corgi is only about gas safety - not relevant here. There exists the Institute Of Plumbers which is a charity and not a regulatory body, so has no real powers. If you are dealing with a company you may get somewhere by constant hassling. An individual - who knows?

Perhaps the least undesirable route would be to employ a Heating Engineer to do the cleaning now, before much damage is done, and pay the going rate. The figure comes from British Gas's lead - about £400.
Inhibitor to inject through a radiator vent hole costs about £20.

Ian · Moderator Joined: 18 Feb 2003 Posts: 32 Location: wigan