Just how clean is that water container?

If you’re drinking water when recreating (and you should be), how important is choice of container to the cleanliness of the water? Proponents of water bottles certainly show how much easier they are to clean than your average hydration bladder. But does this make a difference?

Well, according to this paper, no. At least not in this convenience sample of people using one of 3 trailheads outside Albuquerque, NM. They were cyclists, hikers, or runners who were simply asked if they could have their water tested. They ended up with only 67, but that was more than they needed based on a power calculation for 20% difference between the two.
The total CFUs for each type was low (37 for water bottles, 27 for hydration bladders), which made finding a difference difficult without a much larger sample size. And even if it had reached statistical significance, such a small difference in colony forming units likely wouldn’t really matter in the real world.

The authors were correct that multiple potential biases could have been present. These include simply lying to the investigators about cleaning methods to appear “better”,  forgetting how long they’ve owned the container, and missing the more “hardcore” athletes who simply wouldn’t stop for the surveys. Most importantly, since these were trails close to civilization, nearly 90% were filled with municipal water that may have slightly disinfected the device.

The main problem I have with this is they didn’t get the water through the tube in the group using hydration bladders. Certainly the rationale was there (trying to avoid contamination from oral flora), but the tubing is the hardest part to clean and thus most likely to be colonized. Future studies should look into a way of controlling for this while measuring the water from the orifice used for consumption.

Based on this study, if you’re recreating near a city using municipal water, it doesn’t matter what type of container you put your water in. Just make sure and clean it regularly. I agree with the authors that applying this data to water that is potentially contaminated is more troublesome. It probably still doesn’t matter, as you should be decontaminating that water via whatever method you choose anyway.

A comparison of bacterial colony-forming units in water bottles and hydration bags among outdoor enthusiasts.
http://www.ncbi.nlm.nih.gov/pubmed/20030447

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