I got some Spa Flex Hose 1 inch from Lows and woul like to know what is the proper way to glue Spa Flex to PVC elbows,ball valves, unions ? Do you sand down the inside of the PVC to get better fittings ? If you push the Spa Flex in you will only get 3/4 of the way in , would that be safe enough? Is it better to prime and glue the inside of the pvc and the end of the spa flex before insertion for good strong cement of both?