I switched my little man from the PP pellet's to the PML diet (which I think I am eventually going to switch to BML ) but since the switch, he has drank almost no water. The food is almost half water so I'm not extremely concerned, but maybe I should be? He's going to the bathroom just as much, his poop looks a little darker since the switch.

Have you tried a tent test (pinch skin between shoulders to see how long it stays up), to check to make sure he's hydrated?

Video of How to Tent Test

Hopefully someone else can give some more insight.

They won't drink as much water when you get them off of pellets, bc they won't need it. The pellet food is really dry, so they have to drink more water to make up for it. My gliders eat HPW and they don't drink much water at all.. I have 4 and one of those tiny water bottles and the water gets changed to freshen it, not because they run out.

Sara Sue is right. They get the majority of their water from their new diet, fruits and veggies. Have you noticed dried f/v left around in the morning? If it makes you feel better, do a tent test every so often. One of my cages doesn't drink much at all but that's because they attack the fruits. The other cage eats everything and still drinks quite a bit.