Re: Vacumm Pups Source

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi Jan, Ed!

>Just want to pop in here... with a cheap aspirator you can reach
about 50
>Torr with a household water faucet, and maybe can do better with
higher
>water pressure and a better constructed aspirator. <snip>

Absolutely right.  I've found the all-glass ones to be significantly
better than the plastic ones.  Also if you have direct mains water
pressure (kitchen taps are usually direct-to-mains and the one out in
my garage is too) it does indeed make a big difference to running the
thing off a header tank in the attic.  Finally, the water temperature
makes a difference too, because of the vapour pressure variations.  A
pump which would pull say 25mmHg in summer would get down to better
than 15mmHg in winter, once I measured 8mmHg with a really excellent
glass pump, but the water temperature was only around 4C (it was a bit
nippy in the lab too ;-)

Dunckx
Geek#1113 (G-1)