The ERP series of valved outlet assemblies connects the aeration diffusers to the compressor. It includes a pressure relief valve that will prevent pressure buildup in the line if the diffuser(s) get clogged, saving compressor burnout.
The ERP1V includes a swivel union and pressure relief valve but does not include a gate valve for the diffuser.
The ERP2V - ERP6V include the swivel union, pressure relief valve, and a gate valve for each diffuser connection, allowing you to tweak the amount of air going to each diffuser and making it easy to take any diffuser offline for maintenance without shutting down the rest of the system.