Bob's method is really sound.  Just don't be confused by temperature or barometric changes.  Check both temp and barometer readings at the start and end to be sure that your leak or lack of leak is not just Charles's Law,

V₁ / T₁ = V₂ / T_2,

or Gay-Lussac's Law,

P₁ / T₁ = P₂ / T_2,

talking.

Barry Knotts



Robert Pastusek wrote:

Bryan wrote:

I am in the middle of testing my fuel tanks for leaks with a vacuum
pump.  How long is long enough to hold vacuum to prove it wont leak?


Be very careful with the vacuum pump. More than one Lancair builder has
"imploded" his wing tanks with this not-so tried and true method. There have