On 25/10/2012 13:21, Alibaba wrote:
harry wrote in news:56002e72-ef88-4af1-bac1-
:

Why not get a water softener and all you need then is salt?

That's an idea; thanks. I've just been searching for a conversation I had
about this subject a few years ago, and there was a heated (and
inconclusive) debate about whether phosphate dosers and water softeners
were more effective than ion exchange water softeners. No-one involved in
the discussion could point to any controlled tests to back up their
opinions. Anyone got any educated (or fist-hand experience) opinions on
this question?

A phosphate dosing unit won't soften the water. It will stop the scale
precipitation out when its heated, but let the water dry on a surface
and it will still leave marks etc.

In a previous house, I installed a phosphate doser, thinking it would
prevent my heat exchanger from scaling up. One year later my boiler's
heat exchanger was clogged again, as it had done almost every year
previously. Having said that, I think it was partly clogged with iron
oxide (i.e., black rust).

It could clog with iron oxide on the primary side of the HE. There
should be none in the HW side. But that would be a separate problem
caused by corrosion in the heating system.

Perhaps water softeners don't inhibit the
formation of iron oxide. Is there anything that inhibits the formation of
iron oxide, as well as limescale, in heat exchangers (apart from things
like Fernox, which obviously can't be added to mains drinking water.

The primary side, can be dosed with inhibitor like Fernox - you will not
be drinking that. The HW side of the exchanger can be protected from
scale by the phosphate unit. Unless there is something odd about your
local water supply, there should be no iron oxide in that. If that is
proving to be a problem then you need a particulate filter on the cold
supply (BWS do a matching unit with a cartridge for that - you can get
them as a pair from SF)

--
Cheers,

John.

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