David wrote in message ...

When I moved in about 2 years ago, the bowl below the water line was
badly stained a brown colour. Thinking it was the obvious, I
eventually took the plunge to see if it would be easy to remove. It
simply wiped off and I had a perfectly white bowl.
However, the bowl is again starting to stain. It is flushed after
every use and the water is clear, there is no staining in the cistern.
Using a toilet brush would prevent anything building up over time, but
what would be causing it?
Get some citric acid crystals from the chemist (100 gms about 60p IIRC). Tip
the whole lot into the bowl and use a long handled washing up brush to get
it up to the rim. You may need to do this on and off for a couple of hours.
If you can be bothered to temporarily block the WC with a towel or
something, you can just leave it overnight.
IME this treatment lasts for a good couple of years. Once you get rid of the
salts, the colour can't build up so easily.