I'm not sure as to what you mean by "separating from his stomach"
If you mean his tube comes out and had to be pushed back, then this is not normal at all. PEG tubes have a fastener to keep them in the stomach, either a wire (pig tail) or a balloon.
Here is a simple chart that that can walk you thru the PEG issues
PEG complication chart
Also you should take the time to read all the posts in this thread here at OCF where I posted this chart. There is a link to an extensive 55 page manual prepared by Canada that is very informative also.
OCF thread on Peg troubles
Unfortunately, most doctors and hospitals never prepare nor follow up on PEG tubes, with some notable exceptions like DonB's hospital.
charm