Jeff Chorniak wrote:
> Try a vacuum pump.


Careful! On a thinwall tank you may well collapse the sidewall. They're
designed to resist outward pressure, not inward. Think of the strength
of a 2 liter soda bottle against bursting vs. how easy it is to deform
it with your fingers. No experience to go by, just some basic engineering.

--


Mike MTM, Cokesbury, New Jersey, USA