Bruce, I am new to this group, and would agree that phosphoric acid is great at de-scaling, but the problem is that when it dissolves the calcium carbonate deposits (i.e. fur) it is creating calcium phosphate. My novice understanding of the new BW licence conditions is that we must not discharge phosphates into the canals - there's the problem! By the way, I must point out that citric acid is not a strong acid. You might use it concentrated rather than dilute, but is never concentrated. (Sorry about that: call it the pedantry of a science teacher if you like!) Kind regards, Keith Norman
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