I have gotten my dog used to drinking out of my camelback tube and there is very little waste if I don't squeeze the tube and spray too much water. also it is more comfortable for me to wear the backpack for the camelback under my vest rather than having my vest heavy with the water bottles I use to carry. I water my dog often (20-30 minuttes max between watering) so the 2.5 litre capacity of the camelback is a big plus aswell.

-Scott