I just spent time replacing all 20 check valves that went to the product and week for the TF and FB, and I still have the same problem! When the brush is being used, foam+air is coming out of the check valve. I made sure that it was installed the correct direction, and it is the fluid controls check valve that I have used many times with no issues. Also when the weep is on, water is running out of the chemical line check valve. I was shocked to start with that all of the original check valves would have failed, but figured they were old. What are the odds I received 20 brand new check valves that don't work? I don't believe that the check valves are bad (old or new ones) so something else has to be the issue. Problem is, I have no idea what the heck else it could be. A check valve is a simple device and shouldn't allow product or air to pass through the wrong way. Any suggestions/tips? I gave up for now until I can think of something else to try. Worst part is that the water is going into my air lines, so my regulators are going bad right and left because of all the water.