Buy a Solvent Weld 40mm (Actual Pipe Size is 43mm) Waste Pipe 90 Degree Knuckle Bend - Black from a large range of Knuckles in our Waste Pipe section. IMPORTANT NOTE: Solvent Weld Waste Pipe fitting sizes are often stated in metric standard measurements, however the actual pipe size is measured in imperial. The three options are as follows - 32mm Solvent Weld Pipe actually measure 1 1/4 inchs or 36mm, 40mm Solvent Weld Pipe actually measure 1 1/2 inchs or 43mm, 50mm Solvent Weld pipe actually measure 2 inchs or 56mm. In addition if the term "ABS" is printed on the pipe this identifies the pipe as solvent weld waste pipe.