The Falls & Boiling Pots Pe'epe'e Falls are in Hilo, near downtown. The river where the falls plunge is called Wailuku. This is also the longest river in Hawaii with 29 km.

Falls & Boiling Pots Pe'epe'e is in a rougher part of the River. The water falls over falls Pe'epe'e and enters a region of rapid (Boiling Pot), where the water then rushes through the rocks of hardened lava and lava tubes to bubble. There is a path that leads around the river, but it is too dangerous to approach the lava tubes. Several drownings have occurred there.

Ok first things first. Do NOT go around calling this PeePee falls. That's now how you say it. It's pronounced Pay-a Pay-a Falls. Pe'epe'e is an idyllic waterfall and deep pool. There is not a whole lot of information on this area mainly because it is so close to Boiling Pots and Rainbow Falls. Here is a blurb about the area:
Wailuku River State Park is off Waianuenue Avenue, downtown Hilo; Boiling Pots Area at end of Peepee Falls Drive; Rainbow Falls on Rainbow Drive; Peepee Falls is approximately one mile beyond Rainbow Falls.

Direction

Take the right fork after Mile Marker 1 on Waianuenue Avenue in downtown Hilo and follow the signs to Rainbow Falls. Continue past Rainbow Falls for approximately one mile to Peepee Falls.