You’re making this harder than it should be. I just revamped my manual blow down system. I put 2 “T”’s in the weep system just downstream of the weep solenoid valve, one for air blow down and the other for the windshield washer field injection from the
Flojet pump. I made a manifold to supply air to the blow down and the
Flojet. So if I want to blow down the system with washer fluid all I have to do is close the ball valve for the weep water, open the air ball valve and blow air into the weep system, than close the ball valve and open the ball valve for the washer fluid and open the air to the
Flojet pump and blow down everything.