Makes sense! After hours of searching someone just pointed this out to me:Near the end of the run, just before the 1/4" goes into the sump I added the 3/8" line and placed the 1/4" into it and have the 3/8" running to the sump. I changed pumps to an apex pmup and it works like a champ, no check valve needed.
ATK Siphon Break
ATK Siphon Break Replacement This is the 1/4" to 1/4" push-fit adapter siphon break
shop.neptunesystems.com
So that’s an option too I guess. Couldn’t find that with any search terms I was using and I’ve done the search more than once. I’m using the pmup as well; dumbest name for a pump ever, but it has great head height!