Well, the problem here is 40" H2O below atmospheric is less than 3" Hg. In a message dated 4/16/2004 5:46:02 PM Eastern Standard Time, larry@forman.net writes: I wonder if we are really talking about inches of H2O, which seems a little more believable. I did take the gauge and compare it to another vacuum gauge and they recorded similar values, so the gauge is likely close. -- Larry