Morglum, if you go past a new neighborhood to the area where the next phase of a development is having water and sewer services installed, (large track hoes and no sidewalks are good signs) there is usually a cut off pile of pipe scraps somewhere. I would advise going in the daytime while the crews are working and just talk to the crew foreman. They are usually happy to have you take some scrap pipe away rather than having to pay disposal fees.
When you get to the pipe cut off pile look for pastel green (sewer) pipe which is about the right thickness. The blue (water) pipe is way too heavy/thick as it is designed to contain quite a bit of pressure. If you are lucky (or have a sharp eye) you might even find some white 4" electrical conduit pipe to use for the riser in your aeration system. All of these materials can be found past new house construction. You will be driving on a dirt or gravel trail to get there most likely.
Everything should be made as simple as possible, but not one bit simpler. - Albert Einstein