There were no sources of water close enough to us, so I had to go a bit of distance to find a lake on a mountain. I got it down nearly to our base and then it just stops propagating the water across the ducts...

If there is a limit, what is that limit?

the limit is defined in the config. I believe currently it's set to 128 blocks but you can adjust it to be anything you want.

Thank you, I will adjust that