When do I need a hydration pack for running?
Use a hydration pack or vest for runs longer than 90 minutes, especially in heat, on trails, or anywhere without water stops. Vests (Salomon, Ultimate Direction, Nathan) are more comfortable than backpacks for running. Start with a 5L vest that holds soft flasks; upgrade to 12L for ultras.
A hydration pack becomes necessary when you can't reasonably carry water in hand or rely on water stops. The threshold is usually runs over 90 minutes, trail runs of any length, hot-weather runs over 60 minutes, and self-supported long efforts. Handheld bottles (250-600 ml) work for runs up to 90 minutes on flat city routes but get annoying on longer efforts. Running-specific vests distribute weight across the chest and shoulders, not the lower back, so they don't bounce or chafe like backpacks. Top brands: Salomon (the standard — Adv Skin 5 and 12 are benchmark vests), Ultimate Direction, Nathan, and CamelBak Zephyr. Capacity: 5L vest holds 1-1.5 liters of water plus gels, keys, phone — sufficient for half marathons, long runs up to 25 km, and short trail races. 12L vest for marathons, long trail runs, and ultras — holds 1.5-2.5 liters plus rain jacket, extra food, poles. Buy one with soft flasks (flexible bottles that don't slosh) rather than bladders — flasks are easier to fill, clean, and monitor. Fit matters: try it on with full water load, make sure it's snug without chafing. Vests feel weird for the first run, then become invisible. Expect 6,000-15,000 INR for a good 5L vest. For ultras, consider two soft flasks up front and a bladder in back for maximum capacity.