Because it can possibly affect aluminium components, eg. heat exchangers - boiler manufacturers advise against it's use.
I'm presuming that you mean the water that goes in cold from the mains, and comes out of the hot taps, as opposed to the sealed radiator part of ch system?
+1. The soft water dissolves the Aluminium based components away very quickly.
Just supplied a softener to a lovely lady today for future fitting, but only after she spent the morning contacting the various vendors of her rads and towel rails.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local