Still, I have to wonder: is that reasonable of me? And otherwise, is it expected to let your pet sharing the same water source with human?
In reality, though, all kind of other gross things are going to get on outdoor fountains even if we keep the dogs away, not the least of which comes from the other people who used them before you.
My understanding (and this is just what I've heard, not something I've investigated) is that if you let a well-maintained fountain run long enough, say 10 seconds, before drinking from it, it's almost certainly fine. Of course, this assumes there isn't any visible contamination on there that the water's flowing through. In short, I don't hesitate to use them if they look OK.
I don't blame you for feeling a bit disgusted, but it's possible that the salivary/gut bacteria of dogs might actually confer a benefit on humans' immune systems. There's a study underway at the University of Arizona to investigate this: http://www.uadogstudy.org/thestudy/
Dogs stereotypically have bad breath but a healthy dog on a healthy diet should smell OK. There are variations within breeds (and probably within humans in how those scents are perceived). Many dogs like to give kisses to express affection so if you get a dog in the future it's something you'll quickly get used to.
Americans are absolutely nuts about what they'll let their pets do.
But it doesn't really matter if the outside of the fountain is clean or not as long as you don't actually put your mouth on the fountain. All you care about is the water pipes inside the fountain, and those are just as clean as water pipes any where else.
http://www.snopes.com/critters/wild/dogmouth.asp
> All you care about is the water pipes inside the fountain, and those are just as clean as water pipes any where else.
I don't see why they would be, especially on the end close to the outlet. I mean, lots of water pipes don't have an open end, facing upward and at angle, exposed to the outdoor environment. Sure, water fountains have shields over the outlet to minimize environmental contaminants entering them, but the fact that they are in a position to need them is an issue.
Now, it may be that in normal use the additional contamination doesn't significant additional danger (I'd expect this to be true inversely with frequency of use, all else being equal), but I wouldn't think it would be "as clean as water pipes anywhere else".
The burden of proof is on the water fountain (or more specifically, the designers of the water fountain) as to whether drinking from it is safe.
This is not a problem with being overly cautious. This is a problem with an antiquated design.
Sure, some water fountains look old...but I imagine that if you live in a major city, odds are (from a logistical standpoint, unless you live in a new subdivision) the tap water to your house or apartment flows through pipes that are older than that water fountain. A dog drinking from the fountain is gross, but I'm not sure the onus is on the designer to totally prevent people from acting silly.