Flush the injector system
After each use the injector, the chemical valves and the suction hoses must be flushed with clean water
Move the suction hose to a container with clean water.
Set the function selector to foam and spray until only clean water comes out the hose.
Repeat with the function selector set for desinfection and other foam products, if available
On the left a chemical valve that hasn't been flushed properly for a long period.