I don't know if there is a height requirement, but they won't let them go down if they can't swim! I tried to take my niece down wearing one of their life vests and they said nope!
Okay, I called the DLH, and there was actaully a recreation department! (Just interesting to me, I guess!)
They said that there is no height requirement. The splash pool is 4 feet deep. Children can go down the slide as long as they can swim on their own from the bottom of the slide to the ladder. No flotation devices are allowed.