I was out at Philmont this summer...

I carried:
1 L Nalgene
2 L Platypus bladder
3 L Platypus bladder
and a pump filter.

Neither of my platypus have the zip opening -- just the screw on fitting for the hose.

I found that I could remove the bite valve and plug the hose into the filter to fill the bladders.

The upcoming days water outlook determined which vessels I filled.