Hi, all.

We've had a problem with inconsistent flush power on our Am Std
w/Flushmate 501A tank for a quite a while. The upper and lower supply
group had been changed recently due to a leaking pressure regulator in
lower goup, so I assumed that they were still ok. The actuator
cartridge showed no air bubbles during testing.

Tech support at Flushmate suggested cleaning the cartridge. I took the
cartridge out and discovered that one is able to disassemble it most
(if not all) of the way. The innermost control rod (has a ball shaped
bottom w/cross shaped plastic arms) unscrews from the top, allowing
cleaning of most of the surfaces.

After cleaning and inspecting the o-rings (they all looked fine), I
reassembled it. The wording in the online manual is a little more
clear than my printed version regarding how to properly install the
cartridge. It suggested screwing the cartridge in until 1-2 threads of
the tank appear above the body of the cartridge. Then turn on the
water and let the unit fill for 30-40 seconds. If the water doesn't
shut off, turn the cartridge in until the sound just starts tapering
off (like a normal refill). Keep turning it in small increments until
the water finally stops filling. Flush and listen for a complete
refill. If it refills normally, you're done!

We have not had a single sluggish flush since doing this procedure,
though I am unsure as to whether it was the cleaning or the
installation method that has caused the improvement. My guess is that
it was the latter, since there was only a little iron staining on the
cartridge.

So, if you've got similar problems w/your Flushmate, give this a try
before buying a new toilet or Flushmate replacement unit.