Central heating expansion tank and use of soft water

[Machra]

Looking at having a new heat only boiler fitted but we have a water softener and finding it a minefield when it comes to boiler manufacture recommendations and warranties when using soft water. One of the fitters who has been and quoted said we would need to fit a new water pipe direct from the mains outlet (under the kitchen sink) to the expansion tank in the loft. This comes at an increase cost and the pipe would have to run up the kitchen wall into the loft which is not ideal. Another fitter said it would be ok to use the inbuilt bypass on the softener itself when filling the heating system and then replace the ball valve on the expansion tank with a tap. I questioned if this was safe as the ball valve must be there for a reason (to automatically adjust the water in the tank when required). He just shrugged this off saying if the tank needed subsequent filling we could use the inbuilt bypass again. Help please who is correct. Is it safe to replace the ball valve with a tap and cut off the automatic supply to the expansion tank

 

[JohnD]

I'm shortly replacing my 18-year old Viessmann with a new Viessmann. The brochure comments that the Stainless Steel Heat Exchanger is ideal for use with softened water (which I have).

Many older Plumbers think that softened water is bad for boilers.

Possibly they have not read the BSI report on the tests carried out, which exploded that myth.

I will see if I can find the link.

 

[JohnD]

Ah, here it is. Click the link.

Boiler filter and softened water?

We are about to have our combi boiler replaced along with fitting a water softener (The salt type). Can the softened water be used to fill the boiler (Reduce lime scale etc) and what inline filters do people recommend for combi boilers? We live in a very hard water area so want to protect and...

www.diynot.com

 

[JohnD]

I have just checked the Viessmann document, the exact wording in the Benefits section is:


"+ 10 year warranty on heat exchanger

+ Perfect for softened fill water due to its stainless steel heat exchanger."



I did actually choose a Viessmann all those years ago because of the stainless heat exchanger.

 

[Machra]

Thank you for the answers and info. I have received an email direct from Viessmann to say the warranty would not be void by the use of softened water so my concern reacts with the rest of the system (radiators etc). I know we can bypass the softener when the system is filled so that just leaves the issue about soft water entering the system when the F&E tank is automatically topped up with softened water and what that does to the rads etc. I do not know how often and much water is used when the system automatically tops itself up by the F&E tank. Can I assume that unless there is a leak somewhere then there is very little top up and that it is only evaporation of the water in the F&E tank that needs accounting for.

 

[JohnD]

Thank you for the answers and info. I have received an email direct from Viessmann to say the warranty would not be void by the use of softened water so my concern reacts with the rest of the system (radiators etc). I know we can bypass the softener when the system is filled so that just leaves the issue about soft water entering the system when the F&E tank is automatically topped up with softened water and what that does to the rads etc. I do not know how often and much water is used when the system automatically tops itself up by the F&E tank. Can I assume that unless there is a leak somewhere then there is very little top up and that it is only evaporation of the water in the F&E tank that needs accounting for.

The BSI test included test of steel, copper, aluminium and stainless. That covers the rest of your system.

Softened water did no harm.

In UK, corrosion inhibitors are commonly added to the water anyway.