Determine equivalent vacuum for water depth

[Jerry Prothro]

Hello, I need to figure out the max water depth a motor will operate without water ingress. The plan is to use a vacuum pump to create differential pressure and correlate that to water depth. My issue is the correlation between the vacuum and pressure. Can someone please provide a formula for determining the equivalent water pressure which the motor can withstand based on the vacuum I can hold? The Max. Vacuum, of the pump is 25 Inches of Hg.

Thanks

 

[Dr. Courtney]

I'm pretty sure rho g h will be in there somewhere.

 

[insightful]

Mercury is 13.5 times denser than water , so 25 inHG = 337.7 inH₂O = 28 ft of water.