A Y-junction joins a branch into a main line at 45 degrees instead of square-on. The angled entry reduces turbulence at the join compared with a square tee, which matters on lines carrying solids. The 6-inch size joins a same-size branch into a 6-inch main. PVC-U equal Y-junction, sized for 6-inch (BS EN 1329 nominal equivalent). Wall thickness on this bore follows BS EN 1329 soil-pipe wall thickness for this bore, and the socket geometry follows BS EN 1329-1 so it seats correctly against other soil-and-waste PVC-U fittings on the same line.