How to Make a Self-Priming Siphon With a PVC Pipe

Aquarium drain pumps triggered by water level increases can be expensive to purchase and maintain. However, aquariums with sump filtration continuously pump water into the aquarium and require an automatic drain to prevent aquarium overflow and sump pump burnout. You can build a simple PVC siphoning system as an inexpensive alternative, using only supplies available at your local hardware store. The PVC siphon overflow system is self-priming -- as the water level rises, it will be automatically siphoned away to the sump tank.

Cut PVC pipe to create two 24-inch lengths, two 18-inch lengths, one 15-inch length and five 2-inch lengths.

Apply PVC primer to a 1/2-inch wide band around the outside of each end of three 2-inch lengths of PVC and allow to dry according to the manufacturer's recommendations. Apply PVC cement to a 1/2-inch wide band around the outside of each end of a 2-inch length of PVC and twist an elbow connector onto each end -- make sure that the elbows point in the same direction. Repeat the process until you have created three U joints, and allow the joints to dry according to the cement manufacturer's recommendations. Label the U joints as number 1, 2 and 3 for future reference.

Apply PVC primer to each end of the remaining two 2-inch lengths of PVC and allow to dry. Apply PVC cement to each end of a 2-inch length of PVC, insert one end into the end of U joint 3 and twist a tee joint onto the other end so that the top of the tee is in line with the U joint. Apply PVC cement to each end of the final 2-inch length of PVC, and twist the PVC into the side arm of the tee joint. Twist an elbow joint onto the other end of the PVC, so that the elbow points downward toward U joint 3. Allow the joints to dry.

Apply PVC primer to one end of each of the two 24-inch lengths of PVC and allow to dry. Apply PVC cement to one end of each 24-inch length of PVC and twist the pipes into opposite ends of U joint 1. Allow the joints to dry.

Apply PVC primer to the end of one of the 24-inch lengths of PVC attached to U joint 1 and allow to dry. Apply PVC cement to the 24-inch length of PVC and twist U joint 2 onto the end of the pipe, so that U joint 2 is perpendicular to U joint 1. Allow the joints to dry.

Apply PVC primer to the end of an 18-inch length of PVC and allow to dry. Apply PVC cement to the 18-inch length of PVC and twist the pipe into the open end of U joint 2. Allow the joints to dry.

Apply PVC primer to the other end of the 18-inch length of PVC and allow to dry. Apply PVC cement to the 18-inch length of PVC and twist the open end (i.e., tee not attached) of U joint 3 onto the end of the pipe, so that U joint 3 is perpendicular to U joint 2. Allow the joints to dry.

Apply PVC primer to one end of the remaining 18-inch and 15-inch length of PVC, and allow to dry. Apply PVC cement to the 15-inch length of PVC and twist the pipe into the open end of the tee joint attached to U joint 3. Apply PVC cement to the 18-inch length of PVC and twist the pipe into the open end of the elbow joint connected to the tee joint attached to U joint 3. Allow the joints to dry.

Place the finished PVC siphon over the back wall of the aquarium, so that U joint 1 sits on the aquarium substrate, U joint 2 rests on the top edge of the back wall and U joint 3 splits to a vertical vent pipe and a drain pipe. Locate the open drain pipe that projects upward from U joint 1 and cut the pipe to the desired water level -- cover the opening with plastic mesh secured into place with zip ties.

Drill a hole in the PVC cap and place the cap on the vent pipe projecting from U joint 3. Connect the drain pipe to the sump tank using additional pipes as needed.