This shows the spray/prime valves.
The left valve can be turned from prime to spray.
If the spray/prime valve is turned to the spray position.
Chemical comes from the pump to the valve, to the flow monitor to the mixer.
If the spray/prime is turned to prime position.
Chemical flows from the pump to the spray/prime valve, to the return valve, from the return valve to the tank you selected.
It is very important not to turn theses valves if the pump is running!!