I got my two pumps from a local surplus store for 45 dollar each. They're actually supposed to be used as compressors but we have them hooked up backwards and they actually pull a vacuum down to about 27" which is pretty dang good I think. The CFM's aren't important because you're not going to be using this like a shop vac. You're going to pull a vacuum, store it, then unleash it on the oil. Basically the CFMs will just determine how long you have to stand around and wait to build your vacuum. For my 60 gallon propane tank, it takes roughly 20 minutes to pull a 27" vacuum with one pump. It fills completely with oil, if i turn the pump back on half way through the sucking of the oil, in about 3 minutes. We use a 1.5 inch hose which comes into the propane tank through a 1.5 inch port. The hose is just a blue pool hose. It was the only hose we could find that wouldn't collapse under the vacuum. The hose is 50 feet long and to kinda pre prime the system we pull a vacuum on the hose aswell. We just have a valve at the end of the hose that we open to pull the oil in.
To get the oil out of the propane tank, we have a tube that runs to the bottom of the tank, like a straw in a drink, so when the oil gets sucked in, it fills the tank from the bottom up. So to empty it we just pressurize the propane tank and push all the oil back out and up that tube. Emptying the 50 gallons of oil takes about 45 seconds as we pressurize the propane tank to 90psi.
Anyways, just look for a pump that can pull a large vacuum, not necessarily fast.
http://www.gastmfg.com/literature.html
That is the people that make mine. They're nice because they're oilless so can be mounted anywhere.
