how to: replace a diaphragm

On this page we go over the replacement of rubber diaphragms. Remember, these units go through a lot of abuse, running for months on end and vibrating at an incredible rate. It is amazing that they last at all. Most manufacturers recommend a routine maintenance replacement from 1-2 years. The unit may appear to work fine motor wise, but output can be at a reduced rate due to stretching of the rubber

Also of note, some manufacturers of smaller air pumps don't sell replacement diaphragms for their units. This is essence makes them throw away items. Sometimes spending a little more money is a better option in the long run if the option to obtain new diaphragms is available

Although this page deals with a Hagen Optima air pump, this general procedure can be followed with most air pumps. For more information, see the aeration page
  • Remove the screws from the bottom of the uni
  • With the the housing lifted off, remove the 1 screw near the air output
  • To remove the metal housing, 2 other screws from the opposite side need to be removed
  • Carefully lift the metal housing. Be cognizant of the wiring which stays attached
  • There is a single screw holding the diaphragm in place
  • With the screw removed, the diaphragm should be easy to work out
  • Spread the armature and you will be able to see the split rubber
  • Screw the new diaphragm into place
  • The place holder for the nipple needs to be set - you don't want "spare parts"
  • Replace the rear screws
  • Replace the last screw to secure the metal housing
  • Seat the body together and just replace 2 of the screws
  • Plug in the unit and adjust the output to high
  • Test the unit for a good stream of air with your finger
  • Once you have confirmed the unit is working properly, replace the rest of the screws at the bottom of the air pump


Testing Performance
To test if an air pump needs diaphragms replacement, attach an air line and place it right at the surface of the water. You may see air bubbles. As you lower the house under water, back pressure increases. It is at this point with split diaphragms that the air bubble may stop as air take the path of least resistance and escapes out of the compromised diaphragm

Expect to take about 15 minutes to complete this replacement task