Water softeners are now commonly used, especially in hard water areas around the UK. If you intend to use a softener unit with a condensing boiler, you must remember that it would be unwise to fill your central heating system with such water. This change in the ph level will impact the longevity of your central heating system and pipework. Therefore, it is wise when adding water using the filling loop to your condensing boiler, that this is fitted before the softener unit.