I have a well, which I was installing a pressure gauge on. All was going fine until some crud fell into the pipe leading to the house. More specifically, it was a thin piece of concrete about the size of half a credit card. It was flat and thin, and very brittle.

After unsuccessfully trying to fish it out, I ended up just finishing my work and turning on an outside faucet for a long while to (hopefully) flush it all out.

My question is: do you think I need be concerned about this? I have not yet noticed any ill effects, but I am quite nervous. I'm hoping that because it was so brittle, it will be broken into pieces and flow through the system. I am also hoping that perhaps being in water for extended periods will help it soften up and flow through. I have an aerator and water softener in the garage which I'm also worried may get clogged from it, if it makes it that far (though I did shut off water to the house when flushing the system out).

THANKS!

Are there any screens or filters between the pump and the house that I could check? I suspect it's probably sitting harmlessly at the bottom of the main line, but better safe than sorry.

I would check the inlet on the first piece of equipment that chunk could have entered.
The concrete probably won't dissolve, but it will likely get caught in the first coarse screen or filter it encounters. Otherwise, it could get lodged somewhere and never become a factor other than a (hopefully) minor restriction.

The water main to the house is 1 1/4". Do you think there is enough water movement to push the debris along, or do you think it would just settle at the bottom of the pipe?

I don't think diameter is so much a factor as volume/pressure.
If it does get caught somewhere, sediment collecting may become an issue, but that could take some time. If you haven't seen any concerns yet, you may never, I hope!

Hah... today I checked the faucet and found some small chips of concrete. I guess at least part of it has made it's way through the system!