Pond Boss Forums POND CONSTRUCTION Building a dam Pipe overflow?

As Ric suggested, I'd use Schedule 40 (PVC). Large metal pipes would also be susceptible to freeze damage (more/less - I don't know) and are heavier and harder to work with. If you get a freeze event every few years that trashed the plastic pipe at the waterline, you can cut it off and glue in replacement pieces as needed pretty easy. It would be much harder for a non-plumber to do the same with metal (heck, find ANYBODY not using plastic for soil pipe in houses nowadays!).

I suggest you see what fittings are available and plan your drain around them. In addition to looking at places such as Lowe's and Home Depot, look for someplace specializing in drain and tile supplies. Our local supplier is titled something like "Discount Tile and Drainage" - they had EVERYTHING we needed for our pond drain, at good prices.

Paint any plastic pipe exposed above ground/water to help prevent deterioration by ultraviolet light. There's a post here somewhere in the archives that talks about sunlight resistance of various types of plastic pipe, but I'd paint whatever I used, thinking it couldn't hurt.