I was given a pair of 50 US gallon stock tanks -
My hubby installed ball valves on both. The one I use one for Muscovy ducks, which free-range, has a "T" leading to two 1 1/4" pipes which I drilled holes in, so when I want to drain the tank, it spreads most of the water nicely, before I have to tip the rest out and rinse. I move this one around the field to "irrigate" the areas that need it. The ducks think the draining process is fun to play in, and love splashing in the water.
The one I use for Khaki Campbells, I eventually installed a coupling and a very long pipe that I can move around to water different areas of my dulcis bamboo patch. The Khaki's are too small and flighty to cope with our flying predator load, so they're in a stationary run. My winter goal will be to add at least a second run, and possibly a third so that I can rotate them through these different areas. As it is now, I have to keep adding mulch and periodically shoveling out the muck and moving it to a
compost heap.
Khaki Campbells may not "need" to swim, but they adore their stock tank and often move in to splash before it's even full. I'm a wimp, so dumping the whole tank would have hurt me. A bucket system would work if there were good places to dump water nearby, but the ducks need so much fresh water, the area near their run gets pretty soaked. The new pipe system is much better.
If you can't afford the expense of a stock tank, and don't want anything as flimsy as a wading pool, consider other available free things. It's a balance. I would definitely want something I can tip and clean, but also something that's large enough they can splash in. I do decommission it for the winter due to risk of freezing.