I have 4 tanks connected together with water-bridges. A 190g, 95g, 90g, and 85g tanks. I've tried several methods to build the bridges. I now only use 3/8" clear cell-cast acrylic to build the bridges. I've built them with clear acrylic pipe and pvc elbows also, but I didn't care much for them.
There is a book you can buy online for $10 that tells you how to build them at
http://fishighway.com/. I bought the book and used some of the ideas to make my bridges.
For me, water changes are much easier with water-bridges because I don't have to take water out of each tank. I do about 20% water-change; that's about 100gallons. If I did a bigger change, I'd have to wait for my 50g water-heater to get warm again. I don't have to refill the bridges during each change, the openings for the bridges are about 6" from the top of the tanks.
Filling the bridges with water is easy if you have a length of 3/8" hose.
I have a video of this here-
Click here to watch waterbridge
I have pic's in my link below.