It's not that easy. Let's say you have a compartment with 40.5 cubic meters (a stateroom roughly) filled with 1 atmosphere of pressure gas. You are trying to evacuate that to vacuum using a, say 10cm diameter pipe of x length. If this is part of system that dumps into a larger pipe, the pressure will fall the instant the larger pipe is reached and the flow rate will slow.
It's going to take a while to do that, particularly once the pressure gets close to the vacuum. That means you now have to add pump(s) to the system. Big pumps.
Overall, this is going to be a complex piping system costing (in Traveller terms likely tens of thousands of extra credits to the cost of the ship.
It will also be of marginal effectiveness as you'd have to plan ahead on evacuating a compartment for it to work. It could well take the better part of an hour to pump down a large space like a cargo bay.
Gases don't act like liquids. A closed liquid system has constant pressure on the whole system. Gases in an open system like you propose will vary in pressure.
All this for a very complex, added, system that rarely gets used.