Thanks, This is the first I've done this...I have 2 bay laser 4000's built in 1999. The 3/4 check valve is stainless Parker and seems to holding fine. I can't think of any other place that chemicals can bleed back in from.
Spot free rinse has small amount of chemical bleed on first half of pass. It leaves little spots on surface of vehicle on hood and driver side then goes clean on the rest of the vehicle. All the check valves are good and don't leak back upon checking them. I have two bays and it only happens on...