dwmckee

The National Park System maintains cisterns with manual pumps every 6 - 10 miles on the C&O. The cisterns are treated with Iodine for sanitation. It is perfectly fine to drink but it can have a pretty metallic taste (though very good for your thyroid!). They use Iodine because it does not evaporate like Chlorine does; it does not 'cook out' like chlorine either unfortunately. Iodine tablets are what you would have carried to purify water in the old days before water filters. The park service tests each cistern every 10 - 14 days to ensure the water still meets safe drinking standards. If it goes out of spec they remove the pump handle so the pump cannot be used. Iodine can also give the water an orange color, and you might think it is rust when you see it in a pot. It can also stain clothes and some plastic bottles if the concentration is high enough. Again if there is a handle on the pump then the water has been tested recently and should be safe to drink (even if it tastes a little funny).

The mosquitoes can be really bad of it is a wet summer, but if it has been dry they can be tolerable, though bug spray is still good to have at night.

As Spinnaker said, the GAP is fine for just about any bike with 28MM tires or wider (no asphalt though). The C&O varies a lot and has mud when it has rained. The tow path you ride on is made from mostly clay so it would hold water from seeping out of the canal. The clay has a layer if gravel on top but that layer is worn through to the clay in many places, Where a puddle forms in the clay, the impervious clay makes it like a bath tub, holding the water in it until the puddle finally evaporates. That is why even 5 days after the last rain you still have nasty puddles of muddy water in certain places. If you ride a folder I'd want to have at least 32MM wide tires. You could ride it with narrower (I have) but it gets a lot less enjoyable. Wider than 32MM is even better on both C&O & GAP.