Ok so here we go yet another vacuflush issue. So I I have a 500 SeaRay. I think these are S series where it has the giant tank separated in line with the pump. Now there are two of these set ups. Previous owner replace lines and the problem started in the guest or day head. Just wouldn’t flush water sat in bowl. Pump just ran. Master head flushed fine. Before I got in to the duckbills I realized there was a back flow device after the system before it hits a 90 and meets up with the other head line which then run to the tank. I pulled this off and put a bucket under that line and used a vac to try to pull what I thought might have been caught in pump or the vacuum vessel. It pulled some out but not much. Tried the other way down river so to speak. Nothing. Tried to blow into that downriver line and could tell it wasn’t blowing through. Asked my wife to put her hand on the outside fart filer vent and no air coming through. Went into bilge to remover fart filter and same no air going through. So I turn on the head pump and it’s cycling and pushing some nastiness out. Wife keeps flushing until it’s clear. Put it back together and it flushes once then does same thing. So now I’m thinking clog some where south down the river. Thinking it’s at the 90. I have this drain snake which attaches to a drill motor. I push it down seems to stop at the 90 but thinking that could also be it hitting the 90. Little back and forth which then it moves again. Seems to stop a few times but run the 15 feet of snake out. Pull it back out and nothing stuck to it. When I’ve used it at home to snake the shower drain the rats nest of my wife’s hair come back out lol. So I close it all back up and same issue. So I see that there is another one of these backflows on the mater head line that the guest head line Ts in to. I take that one apart and do the same snake job. I did feel like I pushed something. The 15 feet doesn’t push to the tank though. Connect everything again and now the master head as well as guest head are not flushing. Guessing im pushing it down. so trying to figure next steps. If i disconnect at holding tank and snake back, might just push it back. Was thinking a drain king type device like this to use water pressure to push it : Drain King 186 Unclogs Bathroom Sinks, Showers, and Swimming Pool Drains, 1.5 to 3 Inch https://www.amazon.com/dp/B0000CBIW...abc_HV7CKQ23X66SWKRDFZQT?_encoding=UTF8&psc=1 Do you guys think I’m on the right path?