# Why is water inside a vacuum chamber not boiling?

I have a vacuum that shows a max vacuum gauge reading of 23"Hg when connected to a chamber. When placing room temperature water inside vacuum, the water doesn't boil. I have seen this chart before https://www.engineersedge.com/h2o_boil_pressure.htm which indicates that my vacuum pressure is not enough to boil the water at room temp. The chart states that I would need a vacuum pressure of about 29.12 "Hg to boil water at room temp. I understand this. However, I have seen multiple videos of people using water inside a syringe and being able to adjust the pressure (by adjusting the plunger) enough for the water to boil without the need of a powerful vacuum. How is this possible?

Thanks

• Does the vacuum gauge reading of 23"Hg mean that your chamber is at a pressure of 23"Hg, or does it mean that your chamber is at a pressure that is 23"Hg below atmospheric pressure? – probably_someone Sep 5 '18 at 21:27
• Are you sure that the syringes in the videos didn't contain $warm$ water? – Philip Wood Sep 5 '18 at 21:43
• @PhilipWood I always use alcohol. It's much more dramatic. – JEB Sep 6 '18 at 0:44
• I'm going to guess that you have only a mechanical pump, and that you don't have a high precision gauge to tell you how good your vacuum is. – dmckee Sep 6 '18 at 14:17
• @probably_someone The chamber is at a pressure of 23"Hg below atmospheric pressure. – N. G. R. Sep 10 '18 at 14:38