We have had a similar problem with our Lay Z Spa St Moritz after refilling the tub after Winter break. The cold water filled to the required level and stayed at that level for 36 hours whilst we put in the chemicals and filtered. When we switched on the heat everything was fine until we opened the lid next morning and half of the water had gone. There was a lot of condensation around but after draining and checking every inch of the tub (inside and out) we couldnt see any puncture. It was suggested to us that the drain plug could be the issue so we cut down a polythene freezer bag and dro