Yes, to answer the question, all of our hydration bladders and filters, etc are fully cleaned and disinfected between rentals with a light chlorine wash. So you're not going to "catch" something from the last user. With that out of the way . . .
One key to a happy backpacking experience is availability and convenient access to plenty of water. To make sure you have clean, potable water - that is, the de-bugged kind - you need to treat it with at least a pump water filter to be safe. But what do you do with the water after treatment? Some hikers carry plastic bottles to drink from, which are fine for short trips and day-hikes, or as a supplement to these bladders. For more convenience and carrying capacity though, we recommend renting a water "bladder", which is a bag that will fit in or on your backpack with an attached hose you can draw water from.
We rent a number of different bladders from our inventory, including 3-liter models from Platypus, MSR and Osprey. For those not into the metric thing, that's a tad over 3 quarts, or when filled, is enough to get most hikers thru their walking for the day in moderate temperatures and conditions. But unless you are assured of a ready source of water all along your route, we suggest keeping at least a quart or two on you at all times to be less likely to run out at an inopportune time . . . . which would be anytime you're not around more water. On the other hand, since water weighs about 2 pounds per quart, no point in over-carrying if water sources are readily available.
While we're on that point, how do you know if you're drinking enough water? Well, not just by thirst, but by looking at your pee. That's right, don't just daydream, look down - if it's clear, you're probably adequately hydrated; if it's dark yellow, best be drinking more than your thirst is suggesting to be safe.
The bladders we rent are typically about 18" long by 7" wide, and weigh only about 6 ounces when empty. It's made from a lightweight but tough nylon lined with food-grade polyurethane. The drinking tube with a Bullet Bite Valve (bite down on the end and "inhale") will stay soft and flexible even in freezing temperatures, and has good volume output when drawing a drink. See more pictures and suggestions on use of this rental water bladder.
For more information read our article on hydration and water treatment options. For some third-party user reviews of this and other gear we rent and sell, visit our backpacking and camping user gear review page.