I was searching Dr F&S and found this part number as well. Google lead me to this thread. Is this all that's needed to fix a broken aqualifter? I've had some that get clogged and continue to run for days until I notice. Then, even after cleaning, the pump runs but doesn't actually do anything. Would these fix this? I've just been tossing them and buying new ones.:hmm6:JP just replace the Diaphragm.
F&S Part #CD-21221 $2.49.
It'll work like new!
I keep 2-3 of these kits on hand and replace them as needed.
HTH
Ed