A dishwasher was not emptying. Filters etc all clear. The owner removed the machines flexible waste pipe from the waste stand pipe saying there must be a blockage in the stand pipe. He poured drain cleaner fluid into the standpipe, refitted the flexible waste pipe and ran the dishwasher, all seemed fine. What I don’t understand is that if there was a blockage in the standpipe why didn’t waste water get pumped out the join between the flexible waste pipe and the standpipe, this was only a loose fit. Any one got any ideas.