I talked with a second installer and he agreed with my installer, that nearly every installer in Hawaii connects the return to the drain port. Many installers use a dip tube to create some separation between the return and the feed, my installer doesn't believe in them. While the installers agree that the system may run less efficiently, the rationale has to do with night time heat loss. The claim is that side connect return lines stayed hot at night and that even with check valves (that they claim to stop functioning in on a year or so), the heat traveled up the return line and radiated out the panels. Having the return at the bottom means that the line is cold at night (our backups are off during the night) and heat doesn't travel up the pipe. What do you guys think? Do you see much heat loss with side connects? Our tanks and panels are sized to heat water to well over 140 degrees on a sunny day and provide 100% of the hot water without the backup ever kicking in.