If you're running a chest rig, I might recommend getting a bladder you can dump at spawn and strap a couple cheap surplus USGI canteens to your belt. For me, at least, I prefer to minimize weight with chest rig kits and distribute weight as low as possible. Mags on my chest, water and snivel gear on my waist. You'll have enough water to hold you over on the field and a plentiful reserve back at respawn, you'll be dead often enough at your typical game where hauling 2 liters of weight on your shoulders isn't really necessary.
*Note that this is based on my own personal experience and the amount of water I need to consume in a hard day's play. Your results may vary.