I bought a new Mark VII touchless that was installed about two months ago. Previously, I used a dual pump to mix alkaline and surfactant. My techs had no idea how to accomplish this. I went through a myriad of experiments trying to figure it out. Long story short. Dema makes dual port injectors. I installed them about two weeks ago with the surfactant port below and the alkaline above the center line. Bamm! Working without a hitch since. So, for a $75 box of alkaline and $5 of surfactant I get 55 gallons of presoak. That's better than $600 for 30 gallons.