[A930Rocket]

I’m no plumber, but shouldn’t those 90*’s be wyes?

Also, what size pipe is the large drain...3 or 4”? How many gallons are your toilets? With low flow toilets, the 3” pipe works better, as it helps push the turd down line. New toilets with a four-inch pipe, don’t have enough water behind it, to push the turd down.