I am looking to do a Stenner Chlorine pump install and want to check with the experts... Would one of these two caps be a good place to install the injector? It is the last point before returning to the pool... I figured I can replace the cap with one with an injector installed.. I have 3 returns on the pool... not sure which one serves 2 and which one serves 1. The Puck chlorinator is not in use.