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Ion Exchange Softened Water and Domestic Central Heating Systems

There is ongoing conflict about the suitability of filling the domestic central heating system with ion exchange softened water. Historically, this emanates from the BSi code of practice BS7593, which originated in 1992 (revised in 2006), stating that naturally soft and base-exchange softened water have an increased potential for corrosion and the primary circuit should not be filled with softened water unless a corrosion inhibitor specifically formulated for the purpose is added. And that softened water should not under any circumstances be used where a boiler contains aluminium.

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