They are on a ball valve at the outside of the building. So when it's open every pond will drain. Which is twice to 3 times a day sometimes routine. They love to excrement in the water. Then they can be filled up with placing a hose in just one on the ponds. But I might run a water line to each one with a small ball valve. So a quick turn of that valve and few minutes later they will all be filled up.Do you have a pump on your drains or do you just flush it out with a hose?