Tire and engine cleaner line blows out

[westernparkcarwash]

I have a 4 bay self serve car wash and on bay is always blowing out line for engine/tire cleaner. Seems as if high pressure somehow blow line out.
Is the something in the switch i should check or is there some type of check valve. This one has me stumped and we keep repairing line often.

 

[slash007]

You have a bad check valve. Just look above in that bay and replace it.

 

[westernparkcarwash]

You have a bad check valve. Just look above in that bay and replace it.

Thank you