A car wash with 4 jet wash bays uses, as a rough guide, around 300 L/min of compressed air including margin, and about 450 L/min if you add a service point with a blow gun and a tyre inflator. A compressor of 0.6 to 0.9 m³/min covers this. If a gantry is added to the bays, aim for 1.1 m³/min instead.
Where does the air go in a jet wash bay?
The high pressure water does not come from compressed air: it comes from a pump driven by an electric motor. The air does something else. It opens and closes the programme valves when the customer turns the selector, it foams the product in the brush or the foam lance, and sometimes it feeds the final rinse. That is why a bay uses little air compared with a gantry.
As a rough guide, the usual order of magnitude is 30 to 60 L/min per bay. The exact figure depends on the manufacturer and the programmes offered: it is in the manual. For the rest of the site, our page on compressors for car washes covers each point of use.
Step by step for 4 bays
Step 1: take the high value per bay. Without the manual at hand, start from 60 L/min, the top of the range. A slightly larger compressor is better than foam that fades.
Step 2: count the bays in use together. On a Saturday, all 4 bays can run at once. Count them all: 4 × 60 = 240 L/min.
Step 3: add the service points. One service point with a blow gun (about 150 L/min) and a tyre inflator (about 100 L/min), values from our configurator. These tools work in bursts, so count them at 50 %: (150 + 100) × 50 % = 125 L/min.
Step 4: add the margin. At least 25 % for worn seals and small leaks, which are common in a wet environment.
| Layout | Total | With 25 % margin |
|---|---|---|
| 4 bays only | 240 L/min | 300 L/min |
| 4 bays and 1 service point | 365 L/min | about 455 L/min |
| 4 bays, 1 service point and 1 gantry at 250 L/min | 615 L/min | about 770 L/min |
To convert to m³/min, divide by 1,000: 455 L/min is 0.455 m³/min. Our flow and pressure converter does it for you if the manual uses another unit.
Which compressor for these three cases?
4 bays only: the E 75
The E 75 piston compressor, 7.5 kW delivers 0.9 m³/min on a 180 L receiver. For 300 L/min, it runs about a third of the time even when all 4 bays are busy. The piston unit keeps its rest periods.
4 bays and a service point: the S 55
With 455 L/min and a site open late, demand becomes long and steady. The S 55 screw compressor, 5.5 kW delivers 0.6 m³/min at 8 bar and is built for continuous duty. Its variable speed follows the number of bays in use. Pair it with a receiver sized with our air receiver size calculator and a dryer.
4 bays, a service point and a gantry: the S 75
At 770 L/min, the S 55 is no longer enough. The S 75 screw compressor, 7.5 kW delivers 1.1 m³/min at 8 bar and keeps some reserve. It comes without receiver or dryer. The K 75 4-in-1 gives the same flow with a built-in receiver and dryer.
Calculation pitfalls
- Leaks. Vibrating fittings, worn lance hoses, tired solenoid valves: at a car wash, leaks add up fast and can exceed the consumption of a bay. Our article on detecting and fixing leaks and the leak cost calculator help you put a figure on them.
- Water. A bay whose valve freezes or sticks no longer uses air, but it no longer sells washes either. An air dryer after the receiver is essential. Our article which air dryer to choose helps if some pipes run through the cold.
- Extensions. A fifth bay or a second service point added later changes the calculation. Keep the margin, or choose one model up.
For a complete calculation, use the configurator or go back to our page on compressors for car washes. Then send us the manual for your bays with a quote request.
For your trade: Compressor for car washes.