Hey Kendall, I have a similar set-up however, I use a poly Y and for the surfactant, I installed a 1/4" poly ball valve. If I run a thick soap mixture, I simply leave the poly valve full open.
But here is something else to think about. For downstreaming siding(no split lines. Everything in one tank), I use Elemonator with my SH and water at a 1 oz. per gallon of mix ratio and it will last for several days if kept out of the sun. I have tested left-over mix and five days later, It ate the heck out of green mold on vinyl siding. Not to mention how it made 10 yr. old gutters look brand new. The customers can't believe the difference... In some cases, Neither can I. Simply apply with the injector, Wait three to five minutes and rinse with high pressure or a garden hose...
I have tested this over and over and with the lower temps, Lower humidity and keep it out of the sun, It works!!!!!!!!!
Mike