I had read about the bees prefering "dirty" water, too, so I put out an old dog dish with straw in it for the bees. I've never seen them in it, though. .
It depends what is situations. If bees get plenty of wet nectar, they do not bring water.
If they have some days that they cannot come out for weather, they come out to get water as son as weather is suitable. There are hundreds of bees taking water from leaves.
If bees do not have larvas, they need very little water.
You can calculate in the morning on bad weather, how much bees fly with heavy load. They surely have water inside. Nothings else is to be gathered. They are hundreds per hive.
When I have feeded with pollen bees at spring and snow is on the ground, hives become sick if they do not get water. When snow is melted, there are any problems in this case.
It is not necassary to me give water to bees, but it is nice to watch what are they doing.
At spring bees drop into cold water and somethimes hundreds of dead are seen in pools. If water is warm, they swim to the bank.