Vacuum Hand Pump 

The port plug opening is for vacuum testing or pressure testing.

Get a plug the same size and thread, bore it out and install a nipple in it for a hose to the vacuum pump, or purchase a premade plug or the whole kit from us (priced according to cost of the pump at the time.)

Pump it to neg 15 inches and it should hold indefinitely.
If it does not hold, pressurize it and stick it underwater to see where the leak is.

If it is the plastic, send it back to us to be welded.
If it is the motor seal, replace it.
If it is the o-rings, replace them.
If it is the connections (which it never is unless you screw with them and do not put them back correctly), send that lid to us for redoing.

Any connections need to be held on both sides to tighten or they will back out of their threaded slots.

Connector