Well that is another arguement but its happening and customers are having run back of water due to layering.
You have a 2% fall .......over this you are putting tilesafe then Devi mat which isnt the easiest to handle on the mat then leveling compound not easy to maintain the 2% if its not something you do every day.............
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Virtually every product can be b***ered up and cause problems if its not installed correctly but that can't be a reason for criticising the product itself.