Regulatory Codes require Overfill Protection for all fuel storage tanks. The flow of fuel into a tank must be "automatically shut-off". Additionally, regulatory codes require, and common sense dictates, you provide a means to empty the transfer hose between the supply tank and the transfer pump. The Vmi AST-4010 and AST-4012 Fuel Transfer Controllers provide this with no flow restriction.
The AST-4010 provides overfill protection for a single tank that uses a site mounted, motor starter driven, electric transfer pump. The AST-4012 provides overfill protection for two tanks having a common delivery line, using a single site mounted, motor starter driven, electric transfer pump.