You can probably get by with a 10HP Compressor with a 60 or 80 gallon tank. That will put out about 38 cubic feet of air per minute.How much air supply will you need for 4 bays SS and 1 IBA. Who uses Piston type compared to Rotary screw. Thanks
You want to determine how much cfm each item in the wash will consume then you will know if a 10HP is suitable.
For the little use that a self service wash uses an air compressor, compared to one that is powering air tools all day, I piston air compressor is satisfactory. Screws are for locations like dealership service departments or large body shops both of which use air tools all day.
Hope that helps.
Bud Abraham