Is it ok for dogs to share a water bowl?

Speaking from personal experience only, after 35 years of dogs sharing water bowls...even at the dog park...I've never had anything go wrong. And on a practical level, I can't even imagine how you would "assign" water bowls, and still give everyone the opportunity to have a drink when needed. You know they never drink when YOU think they should...plus "the grass is always greener"...etc.

It's very common to put out two or three water bowls and find that all the dogs want to share the same one. It's just important to ensure the bowls get cleaned with hot soapy water daily (or more often if possible) to prevent urinary infections.

At home where the bowl gets washed and refreshed frequently my pups usually share unless they are attached to their own bowl. However, "out" is a different story. I am really careful about dogs drinking from a communal bowl at a park - I don't want to risk them ingesting a parasite even though that is more likely to come from eating something they shouldn't! Also around communal bowls and taps there's often stagnant water that pools which I try and keep my doggie charges away from in case of the dreaded giardia (which is going around my neighborhood and is not fun to deal with!)

I agree with all the answers above and wanted to add that if you are especially concerned, a pet water fountain might be a good option. With water fountains, you have to be extra cautious about keeping the filters cleaned and changing them, but they come highly recommended to keep water moving, therefore adding oxygen and keeping it from going "stale". Many come with charcoal filters that removes debris and odors from the water and keep it healthy. Plus, the waterfalls in many of the fountains attract dogs to drink more often, supposedly.

Dogs should be taught that they have to share water. Unless the dog has really bad territorial or aggression issues, it shouldn't be a problem. Food can be a little harder to share, but there should never be a reason for a dog to "horde" water.

Most dogs share water just fine, but I will set out two bowls about 6 ft apart if I have a possessive/aggressive dog. He can't guard both bowls at the same time, and after being corrected by me a few times for trying, they usually give up.