Roger: didn't want to start a new thread since my problem is also with the calcium dispenser. I just received it today, put it all together and I think my check valve is defective. I installed it in the correct direction (clear side towards the metering pump, black side towards the calcium dispenser).
What's happening is that almost everytime the metering pump comes on, it forces the spring to collapse and thus plug the line. Do I need the check valve? Do I have this installed correctly? How do I get a replacement check valve?