i have not built mine due to time constraints and biking season is picking up but i have seen some guys on youtube tapping into there brake booster for vacuum and claiming it provided plenty to go off of. i am going to try this to start off with, the stock vacuum pump should pump down to about 18" or so.
as far as the clear water pump i have used one of them to collect and it was SLOW, they are hard to get going since they cannot pull a vacuum to start and once they do they are pumping about 2 gal a min. it took me over half an hour to fill a 55 gallon drum with it and it was transmission fluid. that was with the wast tank 2 ft off the ground with 50ft of 3/4 hose and the 55 gal drum in my truck. wmo is even thicker, on the flip side it makes a nice pump to fill my truck with when it is left in the garage hooked up to my filtering station. it is lower than the tank so it does not need primed every time i use it.