Our bath has not been draining properly for some time and we tried all sorts of remedies claiming to be the one that would work including putting bicarbonate of soda down the plughole followed by white vinegar and leaving it for an hour or so before flushing with a full kettle of boiling water.
When shopping in Asda on Saturday I had a look to see what was available commercially and they had a large bottle of Mr Muscle Max Gel Unblocker – currently £5 on rollback - but it warned that the product was harmful and would corrode chrome, so no use then.
They also had Cillit Bang Drain Unblocker Gel – currently £3 on rollback - and not harmful, so I got two of those and when I got home I used one full bottle following the instructions to the letter and it WORKED. I left it a good few hours but when I had a bath that night the water drained without problem and has been fine since. The second bottle is a stand-by in case it happens again in the future. I've seen a few posts where people have tried all kinds of things such as wire coat hangers, buying a special 'snake' tool to do the job, removing the U-pipe and clearing it out. We were almost at that point ourselves but this little bottle of magic saved the day so just wanted to recommend it 