50 PSI is plenty. One location I deal with has them on foam brush, tire cleaner, and presoak, and they do okay but the water pressure is too low. Flow is not an issue as they can handle 14 GPM. That should run at least 20 bays at once on foam brush. FWIW these are DEMA Mix-Rite units which I prefer over the Dosatron. The Dosatron is pretty fragile and they have a bad habit of leaking if you turn off the water supply to work on it. DEMA has a version that has a special piston and housing to handle caustic and abrasive chemical like tire cleaner.