Boilers and water softeners

Nick, you are making a lot of assumptions!

An ion exchange softener normally has only a very small amount of chloride in the softened water and thats no problem to anything. But sometimes they are abused or go out of adjustment or are not maintained and then the chloride level becomes higher. This is only a problem with the secondary heat exchanger on a combi boiler.

The sec HEs are now mostly stainless or copper and are relatively cheap and although the boiler makers will mostly say its not permitted thats to cover themselves and many chose to ignore that advice without much problem.

Few areas are so hard that filling the system with mains water will cause any problem if there is inhibitor and the boiler has been correctly commissioned.

Its a finely balanced argument if its better to fill a system with softened water or with unsoftened water. Generally most people would say use the mains water.

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What about the soft water reaction on the inside of the radiators???
JohnD said:
I rather like the idea of filling with deionised water (I am in a very hard water area). But where do you buy 100 litres of it?

You'd fill with mains water.

The volume of dissolved solids in 100 litres of hard water would be negligible (say 100 litres at 400 mg/l = 40 gms, about 10 teaspoons). Once the system is filled there should be little/no requirement for make-up water to be added. The only systems I've seen that had problems with kettling or boiler failures due to limescale deposits, had undiagnosed problems with leaks and had been taking in make-up water, and dissolved limescale, over a long period of time.

Artificially softened water is more corrosive than untreated mains water.
De-ionized water is corrosive until the inhibitors are added.

With a district heating system, heating a site of several acres, you inevitably get persistent water loss through leaks and hence the recommendation to make-up with de-ionized water. The only site I know where de-ionized water was used for make-up had that its own water deionization plant.

It is common practice for heating contractors in the rural US to buy de-ionized water to fill heating systems, either because the water supply is drawn from wells and is unsuitable or the system needs to have anti-freeze added. Howvere, they buy DI water for about 25c a gallon (last I heard, but some years ago). We pay more in rip-off Britain.
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I have fitted about 10 Hydroflows. As it is electronic I assume it does away with any problems from deposits. One of the reasons I recommend it is its fit and forget benefits. It also claims to work retrospectively??

They cost about £100 and are a very simple DIY fit

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