Unvented cylinder with water softener

[dr_jones]

Is there a definitive answer to this?
We have a stainless steel everflo unvented cylinder hooked up to a Worcester Bosch boiler, and are thinking of getting a water softener as were in quite a hard water area.
I've looked around, but can't seem to find a clear answer as to whether a water softener will cause a corrosion issue with the cylinder.
Also, any advice on water sort of water softener to get for a 4 bed / 3 bathroom house? Some sort of high flow metered unit I guess, but not sure on capacity or vendor.

many thanks

 

[Frelon]

There are many posts on this forum about water softeners, do a search. Remember that buying cheap is buying twice!
Think about a water softener as a long term purchase, I have had them (different makes - Permutit onwards) for 50 years. A block salt (twin cylinder) softener is a big investment that will last for years, but you will be pleased you made the decision!

However, it is sad that many old school plumbers still think that artificially softened water should not be used with modern heating systems as the softened water may damage the heat exchanger.

British Standard 7593:2006 Code of practice for treatment of water in domestic hot water central heating systems was revised to allow the use of any supply waters, including artificially softened water, in central heating systems (including those with aluminium) provided an appropriate corrosion inhibitor is added. Installers are advised to consider hardness of the water being used to fill the system and to check suitability of the inhibitor product.

I recently contacted the manufacturers of my (aluminium heat exchanger) boiler and they stated that it was the chemicals in softened water that caused the corrosion! How out of touch can some of these manufacturers be?

 

[Ric2013]

Baxi (like your boiler manufacturer) won't allow artificially softened water in its aluminium heat exchangers.

The boiler manufacturer is not really being unreasonable in your case: the product was not installed and used in accordance with the installation instructions (assuming the instructions state that softened water must not be used).

Getting back to the OP's post, I think the answer is to ask the cylinder manufacturer for advice. You would expect they would state not to use softened water if they thought the grade of stainless they used would have issues with it. I have my doubts about softeners being useful, however, relative to the initial and ongoing costs of having obe. I live in a "very hard" area, with no softener:

	327.765 mg/l (or parts per million)	:Calcium Carbonate
	131.106 mg/l (or parts per million)	:Calcium
	22.812 °C	egrees Clark
	32.777 °F	egrees French
	18.617 °dH	egrees German
	3.278 mmol/l	:Millimoles

and recently descaled my 8-year old electric shower, which was virtually unaffected by scale. My DHW cylinder was also almost clean after 15 years of use. I suspect there is more to it than this, as the local town-centre water (which is softer) seems to create more problems with limescale, based on what I have seen in a customer's house in that area.

 

[Frelon]

Just in case you were still wondering....

Worcester Bosch state "You can have a water softener in combination with our boiler as it will prevent the hot water circuit from scaling up and losing efficiency. However, the central heating circuit should be filled with hard water and a chemical inhibitor. This can be done by using the water softener bypass when filling or topping up. Alternatively, the filling loop feed can be connected upstream of the water softener."