watchdog

hi there, i'm new to this forum and found it while trying to troubleshoot my problem. i have a softub portable spa and just had it recovered/relined, when i got it back and hooked it up again i found the air control valve wasnt working. i took the valve off and it seems to be functioning properly. but the air line to the tub is actually pumping water out of the tub and up towards the air valve? my thinking is that this is wrong and that the water pressure is keeping the air valve closed. if i shut down the powerpack i can blow through the air line and air will come out the jets. is there a check valve that the spa company didnt replace??? if anyone has any suggestions i would be most gratefull, thanks in advance.