check to make sure you have them connected correctly before callin them bad. they are ridiculously simple so i dont see how they could be defective without it being obvious.
i hooked mine up wrong a few times (supply in delivery side and the opposite) and ended up with goofy crap happening.
did you ever have a break in the line and used a ptc fitting to fix it? I did and i didn't realize but it was a check valve and only flowed one way. I was stomped for days then i remembered that piece.