Air intake is not working

I replaced all the tubing in my old hot tub reusing all 4 old jets. When running the pump on low or high and opening the air valve, I am getting water back flowing out of the air valve instead of the air being taken in and coming out of the jets like normal. Any ideas about what would cause the back flow?

If you have adjustable jets make sure they are open. If they are not adjustable then it could be something clogging the jet venturies such as debri. If that is not the case make sure you have no kinks in any of your plumbing lines coming from the water manifold.