As brian said push/pull is how to recover its quick and easy ive got a 1/2" bottle fitting with a sight glass run the system once the liquid stops shut the system down and recover the remaining vapour i can recover 900 kgs in 4 hours uaing this method
Never rely on shut off valves holding up may be quicker
But its not safe pratice and what can go wrong will go wrong to many cowboys out there cutting corners to win work