Rusty wrote:
Same problem here. Although we've hard water, the rim underside has
always
been cleared of scale by squirting the descaler up into it. The water
comes through a large number of 6 mm holes under the rim so if it's scaled
up, its
above these holes. Tried descaler in the cistern too, but bad idea.

I am now more familiar with the workings of my toilet. More than I used
to be, probably more than I really want to be. There aren't holes in the
rim, just a shelf sort of arrangement, far as I can work out:

..---.
| |
| -- water slooshes around here
'---.
\
\ the bowl


[use a fixed-width font, if you're wondering what that mess is]

Where the water enters the bowl rim, there's some sort of moulded
widget that forces it to shwang off in one direction or the other.
If there's something stopping it from making its full journey to
the other end, there to meet the other half, I'd guess it's scale
part of the way along. Which makes unscrewing the top of the
siphon and pouring descaler down the tube ineffective, as it just
drools round the widget rather than shooting off along the rim.

--
Happy, sad, cross and concentrating.