Rob Waghorn
Hi again Eric. It's obvious the basin and bath waste are connected. As I said yesterday there could be a partial blockage. The basin waste is pulling the trap on the bath when you pull the plug. I would take the trap off the bath and clean it out. I have a wet and dry vac that I use on waste pipes when I've taken the trap off, it gets rid of any blockages and is better than a plunger. Robert