A simple child's desk made of PVC pipe requires four legs and a platform to support a desk top. The easiest method is to make two squares for the sides of the desk and a large rectangle platform to support the top. To determine the height of the desk, have the child sit in the chair you will use, and measure from the floor to his navel. Estimate width and depth based on the space where the desk will be located. A typical all-purpose desk for a child is 30 inches tall, 20 inches deep and 36 inches wide.
Supplies for the PVC child's desk include pipe and fittings. For fittings, purchase four 3-way elbows and four standard elbows. The length of PVC pipe needed depends on your measurements, but get enough for the two side squares and the rectangle on top. For the 30-by-20-by-36-inch desk, you need four 30-inch pieces, four 20-inch pieces and two 36-inch pieces. Get a piece of PVC sheet cut to 20-by-36 inches and 1/2 to 3/4 inch thick. Plastic adhesive, such as liquid nails, finishes your supply list.
Set the four 3-way elbows on the ground. Connect them with two of the 20-inch pipes and the two 36-inch pipes to make a rectangle. Glue the PVC ends before putting them into the fittings. Use two standard elbows, one 20-inch pipe and two 30-inch pipes to make a U-shape. Make a second U-shape with the remaining fittings and pipe. Glue all PVC pipe into the fittings. Attach the rectangle platform to the tops of the U-shaped legs. Glue in place. Apply liquid nails to the top of the rectangle, and set the PVC sheet on it. Press it down firmly to remove any air bubbles. Allow the desk to dry for 6 hours before using it.
To add more stability to a larger desk, consider modifying the design to include a crosspiece to support the center of the desktop. A crosspiece connecting the back leg posts of the desk would also support more weight. Try designing a child's desk that would fit in the corner to save space. That design would require a more triangular configuration.