If I connected the basin, shower, bath waste all have individual strap on boss around the soil waste pipe. I'll use anti vac trap on the basin. Can you use a durgo below the flood level of the floor? As same manufacturers do have them but I've never used them below I've always used applied them to the heightist appliance.
I've got 4" tee coming through the concrete floor which is the foundation of building could I put a aav on top and the other section would be all waste connections. All under the floor?