Abstract: At least one air tank and a tank of a solution to be injected into an irrigation system. Irrigation water is allowed to slowly fill the air tank. As the water rises in the air tank trapped air in the tank is compressed. This compressed air is allowed to pass into the top of the container of solution forcing the solution from the bottom of the container into the irrigation system. An adjustable metering valve controls the amount of solution that passes into the irrigation water and hence the amount of water that can flow into the air tank. The tank capacities are such that when the air tank is filled with water the solution has been exhausted from the solution tank. Drain means is provided in the air tank to drain the water therefrom.

Abstract: A system which combines an additive storage vessel and mixing section containing pressure and suction taps off of a main transfer tube. This allows controlled blending of additive into a fluid stream without external energy or controls. The tank is shaped to allow a stratified layer of fluid to slowly displace the additive. Displacement energy is supplied by a positive pressure tap facing into the flow converting dynamic pressure of fluid flow into increased static pressure and a reduced pressure tap created by facing with the stream flow. Trickle tubes connect the taps to opposite ends of the additive charge, which is slowly pushed and pulled into the fluid stream. Rate of additive supply can be controlled by restrictors, tap orientation or tank orientation. An air relief valve is provided to allow escape of non-pressurized air from tank.