I hav error 21
I had the same issue with Out of Service 21. The pump was making noise during Self-test, then the error. I took the entire thing apart. I removed the pump, cleaned all the plastic/rubber parts, and reassembled. All seems to work now. The final piece that I cleaned was a tiny black washer inside the bottom portion of the plastic assembly that inserts into the pump solenoid. In the bottom of that piece (about 1/2 threaded) you'll see a star-shaped piece of plastic threaded INSIDE the barrel. I turned that out, cleaned the tiny black washer that blocks the hole, cleaned the spring, and turned the star piece back in. That seems to be what fixed it for me. However, error 21 in the manual indicates ANY issue with water flow.
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