Wish I could help but I lost the name of the reasonable plumber who installed my water heater. Funny thing is that it's like half of your post could be me typing. I think we have the same exact water heater. Same problem with an alarm going off almost everyday now. The only difference is that mine is not telling me to get it serviced. I can see where it might be headed though.

Sometimes, I seriously question the water quality out in Plainville. So many are complaining about it. And many had to replace a lot of their water heaters or other fixtures due to heavy sediment?