Aqau medic quad doser ?? And setup

[Douglas]

With my doser(triple) i have check valves, on all the lines. Making sure they're installed accordingly. Check valves are cheap, and keep flow going only one direction, with no air backing up any of the lines.

I recently had the same problem. I have a check valve at the end inside the dosing container and one right before the output to the tube holder.

[Finisher604]

Thanks for all the input sounds like the check valve is the issue