In article ,
"torge conrad maguar" writes:
I north London here the water is quite hard (i.e. a lot of chalk in it), so
we easily get limescale
build up in the bend of the wc bowl.

Using Harpic Limescale Remover has shifted most of it, but that seems to
have left the porcelain area under water a kind of a dirty colour. I then
used a lot more Harpic, but nothing has improved. Although it does seem to
come off a bit with lots of hard brushing. Anyone any idea if this Harpic
could be causing this?

The scale is a mixture of limescale and organic matter which
has embedded itself in it. They require quite different chemicals
to shift them. In the UK, buy a descent scale remover. Sulphamic
acid is the most common scale remover, and you can buy a large
tub of it at a builders/plumbers merchant under the name Furnox
DS-3. This will work out about 100th of the price of all those
kettle descalers you buy which are diluted with sand and other
rubbish. (Sulphamic acid isn't the best choice for descaling
plastic parts, as it can make them go brittle.) Empty the U-trap
by oscilating the water back and forth with a toilet brush.
Dissolve some DS-3 in warm water, and refill the U-trap with it.
A few drops of washing up liquid as a wetting agent might help.
Leave it to do the work for as long as you can. Brushing will
not much help beyond the occasional stir, although at the end,
it might break away undissolved material. Flush away.

If you've still got any dirt left, this will be organic. For
this, repeat the task above using washing machine detergent
(Europe only) or dishwasher detergent (Europe or US). This
will benefit from some light brushwork, and this will also
clean up the toilet brush nicely. Dishwasher detergent can
give you alkali burns, so be careful not to splash it around.

When switching between chemicals, make sure the previous
chemical is completely flushed from the pan and pipework to
avoid any danger of a reaction giving off fumes. Don't use
bleach -- it doesn't clean anything and just makes dirt go
temporarily transparent so you can't see something is still
dirty. It can also react very badly with many other cleaning
agents.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]