If you have the MixAir (some call it soaker hose) type of AirPod it may not have a checkvalve at the diffuser, This is not a good combination for a rotary vane (or any type of compressor)Putting a checkvalve any other place inline with that model of diffuser will not work well either. Having a checkvalve at the pump (intake side) will only keep the pump from running in reverse on startup .Perhaps Cary will wade in on this if your diffuser is an ATI AirPod.Several companies refer to their units as AirPods, My assumption that it is an ATI may not be correct.