I had to do water tower -> sluice-> sluice to the SIDE of the previous one -> water turbine to get any power.

Image at this thread:
http://forum.feed-the-beast.com/threads/agrarian-skies-hardcore-quest-bug-reporting.43625/page-10#post-604026

I am using the 1.10 Agrarian Skies FTB mod pack.

This is more a lack if understanding of how the system works

Can you improve the docs then?

Edit:
I just watched Corerupt83's spotlight.
I guess this line from the wiki: "Sluices will automatically pass pressurised water to any tanks on it's sides."
should read:
"Sluices will automatically pass pressurised water to any tanks/pipes on it's sides but not the front or back."

The front and back aren't considered the sides...