Question

At what pressure does water start boiling at room temp

Answer 1

Water boils under normal atmospheric pressure at 212°F (100°C). Imagine it at 221°F (105°C) but NOT boiling in a pressurized container. If the pressure is quickly reduced, the 221°F (105°C) water at normal pressure will now boil.

Answer 2

Boiling occurs when the vapor pressure reaches or exceeds the surrounding pressure from the atmosphere or whatever else is in contact with the liquid. At standard atmospheric pressure (1 atmosphere = 0.101325 MPa), water boils at approximately 100 degrees Celsius.