Hello Guys. I re-did my plumbing last night on my 180 and so I have for sale ($10) or trade for any coral a 1" Check Valve (same as pictured below). It is to be used horizontal. I used it for about 6 months or so. It is currently in vinegar and water getting cleaned out.
You put that just after your return pump. What this does is that if the power fails or you turn your pump off. the water cannot siphon back through your pump into your sump, and possibly overflow it. Even with airbreaks on returns the siphon still works sometimes. My airbreaks dont work. So without check valve can overflow my sump