Probably getting the 1" pump tomorrow, and then fitting the venturi for the chemicals is next.
Not sure what chemistries you're planning to utilize through your subsurface injection system, but keep in mind that on-board dilution of the product is rarely necessary or beneficial - but will certainly complicate the calibration process.
Most subsurface products are labeled for and applied at rates designated as "x-amount of product per acre-foot". Calibrating the application-rate for undiluted product is challenging enough, but diluting the product aboard the boat will further complicate the calibration process - and the additional onboard water-diluent offers no technical advantage other than allowing (or requiring) more time to distribute the product that it contains.
Instead of an onboard gas pump coupled to a mixing-tank, maybe consider using a low-volume12v pump (ideally with variable-speed controls) to "meter" undiluted product through notably smaller tubing (i.e. 1/4" ID vinyl), which better maintains subsurface depths due to less resistance as it slices through water. This approach greatly reduces onboard equipment-bulk, weight and complexities - and somewhat simplifies the already challenging task of calibration - while the end-result yields the same ppm or ppb concentration within the treated water-column. This tactic even improves chemical handling-safety since there's no need to transfer the concentrated product from its original container.
I have photos of such a system – but not sure how to link them; plus they might be deemed as advertisements - so, let me know if you want to view a pic through some other means.
