6"SDR 35 Water Drain Piping

Since your installation is not a pressure line, and you apparently took care not to damage the pipe while installing it, it should be fine. One issue you might run in to, however, is blockage. If you did not provide for clean outs, and your slope is too great, you could have an issue over time with accumulation of debris, especially anywhere the pipe changes grade or has an elbow, or where you transition from 4 inch to 6 inch pipe.

When I install a rain collection system, I always include a "leaf catcher" arrangement, which is essentially a box containing a wire basket that can be cleaned regularly. Usually where the downspouts transition to the horizontal run. The basket is designed to trap larger debris that can potentially cause blockage. Since I can pretty well guarantee that the owner of the system is not going to always keep the gutters and roof clear of leaves and other such debris, this is a critical feature of a well-designed system.

Another feature that I find useful, especially if one has a long dry season between rain spells, is a bypass on the downspouts that can allow the first bit of water to be discarded. This allows you to "wash" the roof before you start collecting water...

Right - the accumulated roof gunk from dry spells has to be nasty stuff.

This is very impressive work for a personal home. I think 6" is likely over sized for your flow (just for the roof) but hey, maybe you will expand your roof, or other drains may be added. I got a good chuckle out of your attention to detail. Have you ever considered being a contractor? I think you would be amazing! --- MNF process.engineer@yahoo.com