Just thought of one, and my apologies if anyone else has posted this in the mean time. Only works well if blokey has an ensuite.... In fact would be funny to do in shared ablutions
A few days ago, in the Daily Mail (I didnt buy it honest) there was a lady who had bought some swimming pool cleaner.....
....the long and the short of it is....
Empty cistern of water, empty U bend in toilet of water (you can figure that one out.) Pour one of the solutions neat into the cistern, and the other solution into the U bend.....
After matey has done the biz', flushed and is washing his hands, Mount Etna should be about ready to blow the crapper to pieces.
PS lady suffered minor chemical burns due to the fact she was VERY THICK and didnt read the instructions. This prank is completely different and would stand up in court - honest, just ask ol' pr00ne
Ball Cocks, it would appear I was too late to the party Ho Hum. Anyhow, forgot to mention - chemicals from argos, amongst others!