I just finished my setup which used a bunch of Spaflex. Info on where I got it is below. In case you haven't used it before, it is not as nice as it sounds as it is relatively inflexible and has a bind of its own based on the instilled curves. Be sure to leave it out in a hot area and have a hair dryer handy.
Also, you will want to use the cleaner/solvent as your primer (I think yellow can), and the Rain N Shine (light blue can) for your glue. Both are available at HD and Lowes. This recommendation comes from the manufacturer when using Spaflex.
Main benefits in my view:
-When straight absolutely won’t work...
-decreased head pressure from smooth curves
-long runs require no gluing
-no chance of leaks at junctions
We had long horizontal drain runs (about 50'), so I used 2" Spaflex on the drains, and 1.25 on the pump line. The head loss calculator at reefcentral was a big help - be sure to take into account the diameter of your pump line.
Home Depot and Lowes do not stock 2", but often stock 1, 1.25 and 1.5 Spaflex. If you buy a whole box, Home Depot DOES have a discount for the whole box - make them find it versus paying per foot. We did find the 2" locally at Associated Leisure Products - 770-381-2022
Spaflex is working well for us, but was a bit expensive and not nearly as nice to work with as hoped...