Hardside waterbed frames are made of wood and encase the waterbed mattress on all sides. The frame sits atop a pedestal base, also made of wood.
Once the frame of the waterbed is in place on the pedestal, a heater is laid in the center of the area. A liner is then placed inside the frame, so it can catch any water if a leak happens. The mattress is placed in the frame and filled with water.
The water in a waterbed doesn't need to be changed unless the bed is moved. A water conditioner needs to be added to the water to reduce bubble formation and to keep algae from growing in the water.