Sandlock Waterliner with Drain Assembly The Sandlock Waterliner with Drain Assembly is an ultra heavy-duty commercial grade liner which will withstand years and years of active play. The waterliner is for use with the sand table which measures 27 x 47 inches. The form fitted press in design fits snugly into the table. The easy access drain plug is a great accessory as well. Because it's made of HDPE plastic it is easy to maintain and is durable. The main job of the Sandlock Waterline is to keep the sand and water separate and it does a great job on that.