How much psi is used to pump out water on submarines?

Standard emergency blow air tanks hold 3000psi air in them. However, they aren't normally used; during normal surfacing operations, a boat comes to periscope depth, raises its snorkel mast, then forces the water out using a Low Pressure Blower, which is essentially just a large hi-capacity fan. Sea pressure isn't that much above 100', so it takes a lot less pressure to force the water out with the LPB.