Bests & Worsts Reviews from Amazon

I recently bought a 3 pack of these bottles at Costco, using a store credit for a gift return. I thought that the flip-up bottle spout was pretty cool, and my trusty old Camelbak bottle had just died on me. I thought the bottle worked pretty well until the first time it sprayed water all over me in my car. After it soaked me a second time, I decided action must be taken to fix the problem. The problem, upon closer inspection, is this. The bottle top contains a vent in the cap, which allows air to enter the bottle as you sip water out through the straw. Without such a vent, you'd eventually create enough of a vacuum in the bottle that you wouldn't be able to suck any more water out. However, it does not allow air out of the bottle. As a result, the bottle can accumulate large positive air pressures if you drink from it while it's cold in the morning and then let it sit until the weather warms up later in the day. (For those of you who remember basic chemistry, an increase in temperature on a closed container, all other things held constant, results in a proportionally large increase in air pressure.) Given a large amount of extra air pressure in the bottle, upon pressing the button to open the mouthpiece, the system attempts to equalize pressure by forcing water up the straw and onto your lap at high speed. After several attempts to fix the problem, I wound up just removing the black rubber stopper for the air vent. This allows air to enter and leave the bottle, so I won't get squirted again, but it also means that my bottles are no longer fully watertight if inverted. I figure that should be good enough for most car trips. I would say buy a Camelbak bottle instead, or any other sport bottle which doesn't have a straw. In the case of the Camelbak, you are doubly protected by the bite valve (which doesn't allow water out until you are squeezing the mouthpiece with your teeth), and a better-functioning two-way vent in the cap. Other sports bottles which don't have straws will simply vent excess pressure through the mouthpiece upon opening, without having to force any water up and out through a straw.