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The Bullfrog does add air to the jets, the difference is that there is no diverter valve to control the amount of air ( its always on).
Chas and Mr. Dutch Bullfrog tubs draw air from the equipment compartment and there is a separate air line on each jetpack seat. Some jetpacks come with a control valve located on the jetpack. All the jets( most are made by waterway) can still be controled by twisting them on or off just like most other tubs. Chas you are correct, there is a water line and an air line run around the top of the tub,the 2 inch water line connects with two unions and the air line has a 1 inch disconnect. The jet pressure is adjustable but the amount of air is not.
Would there be back pressure on the pump?