Currently many car wash businesses prefer to use a pressure washer or hose and bucket method.   However the business landscape has already begun to change towards requiring eco-friendly practices in the form of water conservation.  Many tunnel car washes are required to reclaim and re-use the 100's of gallons used during a drive-through wash, while small auto detailers are turning towards water-less car wash methods.  However these both have their drawbacks.  The favored hand-wash system is only viable if a water conserving method is used.  That's what makes the steam wash so attractive, yet still this business practice lacks market presence.