another foam gun question - water usage

[Bunky]

I read that most foam guns use about 1.5 gals/min. I have seen videos showing how foam guns work and it seems like they can coat an entire vehicle in about a minute. Is this true? If so the maximum water usage is equal or less than just filling a typical wash bucket.

[Jimmie]

Haven't measured but it sure feels like less water than filling a bucket.