Robert wrote:
The cistern on our 30 year old close-coupled WC cistern is cracked at
the corner of one side and the font and leaking. This will undoubtedly
mean a new WC but I am wondering if I can make a temporary repair to get
us over the next two weeks.

I have successfully "tanked" a cistern, using fibreglass
matting and resin. Get some matting (you can use car
repair kits, but it's cheaper to but matting/resin), and
some resin and catalyst. It's handy to have some cellulose
thinners and cheap 1/2" paintbrushes, too. Cut out shapes
from the matting to approximately fit the inside of the
cistern, with 2" overlaps. Make sure you've a number of
disposable containers to mix the resin in. ISTR I started
at the bottom, with one piece of matting, and overlapped
oblongs for the sides onto it. Make a small amount of
resin (perhaps 1/8 pt., *don't* use too much hardener),
quickly and roughly soak the area of the cistern your
first patch will cover, put on the patch, and stipple in
more resin 'till it's saturated. Don't bother to coat the
mat where it covers holes, BUT the matt *must* be soaked
to the edge of the hole. When one bit is on, do anoother
bit, and continue, ideally not letting the resin cure
completely between patches. Put in another "bottom", and
then sides. When it's solid, cut out any holes (drill and
padsaw). De-nib if necessary around the "holes", and
loosely put the "gubbins" back inside, using more resin
or filler to make sure the washers etc. form a flat bed
to seat on. When it's gone off enough, remove the
"gubbins", make sure the seatings are OK, and put the lot
back together. Fill the crack with clear casting resin,
or just resin with a tiny amount of catalyst so it's not
particularly coloured. Done reasonably well, this job
will last many, many years. I did this to rescue a cracked
cistern in a matching decorated suite. What have I
forgotten? Hm. Cover the crack with tape before you start,
on the outside, so that dirt doesn't get into it and make
it show as a black line. The thinners is for cleaning up
resin that's not rock hard.