Hey Chris, What ever you decide to do I'd go bigger with the drain pipe. It makes me nervous just thinking about it. If you are using a pressure rated pump up a 3/4 return line you should have a much larger drain than 1 inch depending on the size of pump you are using. Go to this site and use the drain size calculator to figure it out, for my peace of mind.
http://www.reefcentral.com/calc/drain.php