Diaphragm kits return the Evolution Aqua Airtech™ pumps to the peak of performance! Linear diaphragm air pumps typically need to be replaced every 12-18 months. If you are frequently replacing diaphragm kits, your pump is likely experiencing excessive back-pressure (i.e. it is pumping more air than the air stone can put out). Unlike water pumps, where an oversized pump is unlikely to cause a problem, oversizing air pumps is a frequent cause of failure. Feel free to contact us for more information.