Airlift pumps, as the name implies, lift water using an air pump instead of a submersible or external water pump. Airlifts save us money and have increased the reliability of our systems. The inventor Glenn Martinez shared his designs with us. We have found them to be well suited to aquaponics for several reasons starting with the fact that they aerate the water while they lift it.
Additional characteristics make these pumps especially well suited to aquaponics. For one, they can handle solids (even gravel) without plugging, burning up, or wearing out. The low-pressure (2-5 psi) air pump that powers the airlift is unaffected by abrasives, fish, or most anything else in the water.
In some situations, an airlift pump may replace a more energy-hungry water pump. Additionally, an inexpensive replacement diaphragm can extend the life of a good quality air pump to ten or fifteen years making them a potential money-saving alternative to conventional water pumps.
Airlift pumps can be made with basic tools and beginner-level skills from parts available in most stores that sell PVC pipe and fittings. The 35 to 80-watt diaphragm air pumps that power them are widely available in larger cities, often at larger aquarium or pond supply stores and on the internet. Airlifts require an air pump that will produce 5-6 psi for initial startup, then run continually at about 2 psi. A diaphragm pump will do this, other high-volume, low-pressure pumps will not provide the initial pressure needed.
One of the airlift designs uses a "well" that can simply be made from a larger diameter closed-end PVC pipe. This well is typically plumbed into the fish tank or sump. It extends several feet deeper than the tank, effectively making a water column that is as deep as the pipe plus the water depth in the tank. The pipe can be in a hole dug next to the tank or placed off the side of a stand that the tank is supported on. Glenn calls this design a "Pipe-In-A-Pipe Pump". It is most efficient in deeper water. The depth required depends on the diameter of the pipe used, head height and desired flow rate. Ours are operating in from 1 to 1.5 meters of water.
When a well is not practical Glenn's "Burper" style airlift works with a non-spring-loaded, one-way flapper valve. Unlike the Pipe-In-A-Pipe Pump, this Burper pump will completely empty a tank if desired.