If you have a slowly refilling water supply that's nearly empty, the dupes will gather as much as they can get, even if it's only a few kg of water, and deliver it to a nearby water-needing structure. This can lead to many dupes wasting an inordinate amount of time just gathering water. Here is a bunch of dupes making a congo line to fetch water for a microbe musher.
It happens a lot with algae as well. Here is a post in Suggestions and Feedback with the same problem:
Set a water-needing structure like a musher or algae to highest priority. Make sure the nearest water is a shallow pool being slowly refilled.