Another interesting observation is that the sand had clumped under the dosing line from the Kalkwasser. I noticed this before, so moved the dosing line. Once again clumped under the dosing line, which was surprising considering the flow was quite vigorous. I’m guessing the circumstance at that point were ideal for precipitation. I tried to recover the clumps but my wife is highly efficient and getting rid of rubbish. My guess is that this precipitation is high in phosphate. No problem, I can induce this precipitation with a bag of sand, I reckon.Very interesting!