On 20/11/2019 09:19, John Rumm wrote:

... Many boiler makers also caution against using
softened water in the primary CH circuits.


Is that still the case? We had an unvented system and a whole-house
water softener installed recently. The plumber said we should always
bypass the softener when repressurising, but I've since found various
pieces on the web saying otherwise, so long as there's inhibitor in the
system

eg https://purechoice.co.uk/blog/can-i-...r-in-my-boiler

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Reentrant