One plumber I work with insists on upgrading to 22mm on mains pipe at least as far as boiler and kitchen, reckons it improves performance of showers etc when mains fed. And as you say, megaflo needs 22mm.
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Actually on reflection, I probably can't run duel circuits off the Viessmann (not Valliant). I presume?
See below for picture of similar valve to mine
View attachment 30666
Actually on reflection, I probably can't run duel circuits off the Viessmann (not Valliant). I presume?
See below for picture of similar valve to mine
View attachment 30666
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