These are the 2 best YouTubes I could find:
https://www.youtube.com/watch?v=M4Xqlh5VoKo
https://www.youtube.com/watch?v=_GIcg-K4mhI
In your case, you can make a water level using about 20' of clear tubing like this:
http://www.lowes.com/pd_443209-104-S...ductId=4566550
Actually it would work best, if you get more tubing that, so you can have a water levels that will stretch 25' or so. But you'll need 2 sets of tubing and a coupler.
Smaller tubing will work, but it's hard to keep the smaller tubing free of air bubbles.
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