Problem: Deposits build up in U bend trap outside which takes waste pipes from kitchen sink, washing machine, dishwasher and hand basin. The deposit is white(ish), and soft. It builds up to such an extent as to block the 4" pipe. It is easily shifted with a piece of hose. Very hot water doesn't appear to dissolve it (?therefore not fat?). We live in a very hard water area.
Questions: apart from physically removing crud (Yuk!) is there an easier way? Chemicals? which ones are best and where to source them? How to prevent this again?