Hi ive been asked to fix a leak on a flush pipe. I’ve never come across the pan type before. It looks like a closed couple but has a short flush pipe at the back. The pipe was clearly cut too short. it appears to be a 2” flush pipe going into the cistern but I looks like it’s 1 1/2” going into the pan. Would this be correct. trying to order a new flush pipe and need to be sure I’m getting the right thing. Any help much appreciated