I have deep water dc pumps and many have stated they can't use them because of the fitting as well. Not sure what the problem is. It says right in the manual for US applications, just use standard US thread and use Teflon tape to get a good seal. Worked just fine for me.
Yea it took me about an hour at lowes ro find that fitting and works great. But I also ordered those fitting off the YouTube video and it was wrong. Wasted 5 days on getting it in.