# Vacuum vessel at 10mbar with a diaphragm pump: do I need a venting valve?

I'm working my way through learning vacuum technology.

I have a 10l vessel which I want to evacuate to < 10mbar. I'll use this diaphragm pump.

Do I need to add a (manual) venting valve to the system, or will switching off the pump do the job?

I am not a vacuum expert, but if you look at the technical data for your pump, you'll find this "Leak rate 6x10-3 Pa m³/s". I take this to mean that your 10 liter = 0.01 m$^3$ vessel will leak at a rate of 0.6 Pa/s. That's pretty slow. You'll want a manual venting value.