There are water pumps that act much like a faucet aspirator. Some fancy
ones are quite expensive ~$4000. others are in the $500-600 range. After
running these things for a few days, dump the water out and refill them.
No Oil, No corrosion in "non corrosive" pumps. Appligen distributes one
(1800-955-1274), as does Markson (1800-528-5114). I think the less
expensive model is made by ATG, inc sorry I can't seem to locate my file
on these. As someone who routinely services our group's vac pumps, it is
my sincere wish that all vacuum pumps where buried in a landfill and
replaced with water aspiration pumps.
I'll see if I can find the file on the ATG things, if interested, e mail
me at dnamaker@ acpub.duke.edu