I have a toilet downstairs and one directly above upstairs.I have noticed that over the last few days when you flush the upstairs one the downstairs one makes funny gurgling noises.They are both on the same drainage path.I had the mains fully cleaned out about 3 months ago.
I have also noticed that when you flush the downstairs toilet it will fill up about 1/2 way and then drain away quite quickly.
Can anyone give me any ideas on how to fix this?