[mmcconnell1618]

Most swimming pools (in ground) are filled once with water and rarely need additional water added. They use much less water than the average sprinkler system. They do require energy (pump and filter systems) and chemicals to keep things balanced but it designed as a closed loop system other than unusual circumstances.

[8note]

Indoor or outdoor?

[mmcconnell1618]

Both. Once filled, they don't generally need additional water unless there is a leak, some evaporates or the pool is drained for maintenance.

[dahfizz]

We had a pool growing up, and we actually had to regularly drain the water because it rained much more than it evaporated. We didn't live in a dessert though, so YMMV.