Toilet air admittance valve.
A tricky job on a recent toilet renovation.
The pipe work had to be lowered, to do this I had to remove the original junction. Inside the 80mm pipe is an air admittance valve to prevent water being pulled from the trap and allowing sewer gases into the house. I had to enlarge the hole to allow enough movement for the new junction to be glued onto the original pipe. After installing a new air admittance valve set above flood rim level of the toilet, I also covered the valve to frost protect. The screws allow the 80mm pipe to be removed to access the valve if needed in the future. The holes are to allow air flow around the valve.
If you're thinking of renovating give me a call. Meeting your plumbing needs.