My sump is a 75 gal
tub so maybe it is easier but I drain my sump and part of my frag tank that is in the basement when I do a water change. I have a ball valve in line that takes drain water and I just turn it on. You could easily do this with the return pump. I have done both ways. I have also dropped a mag7 in the sump to drain it as well. Keeps my carpet upstairs from getting wet
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,