I'm replacing a dead pump and including a new three-port Jandy valve in front of the pump. The pool is slightly below the level of the pool, and if/when I cut the PVC supply lines from the pool to install the new valve, the water will flow out - making it impossible to apply primer and solvent glue. I can plug the skimmer to stop the flow from that line - but not the main drain. Any suggestions would be much appreciated!