For now I'm using 6 vacuum pumps from Grainger but I made holes for 12. I'll use some freeze plugs to fill the holes until I'm ready for the others. The 6 pumps should pull about 400 CFM at 28 inches of water.
Just how do these things work? Is there some sort of vacuum gauge attached to the port being tested? How do you know how much air is being passed through the port?
What and how do you measure 28 inches of water?
Sorry for all the goofy questions but I just don't understand how these things work.