Best tape for temporary leak sealing?

It's called DENZO tape and it's gooey and sticky and hard to clean up after but - by gosh, it works. I keep a spare roll at home, just in case though that knowledge probably isn't much use to you right now.

Good luck!

Nick

There's also self amalgamating tape, which isn't sticky as suck but does what it says. You stretch it to about twice its initail length and wrap it round. Successfully patched a split diskwasher pipe with great success.

Bert Coules presented the following explanation :

If it is like the flush pipes on our two toilets, which had a drip for years, until someone gave me a tip for sealing them a few years ago...

The pipes go into a nylon seal which has a series of flexible rings moulded around it. The rings form the seal between the pan and the pipe, except on there own they do not work very well to completely seal entirely. The tip is to tightly pack the gap between the rings with Plumbers Mait. As pipe and seal is pushed back in the Plumbers Mait will squeeze out and fully seal properly, just scrape of the excess, back into the pot.

Many thanks to everyone for the new replies and advice; much appreciated.

Luckily I have a reel of this stuff from perhaps 40 years ago, no idea what its called generically or anything, to buy now. Hessian band heavily impregnated with green clay/mastic/putty?, that never sets . Wrap it round a few times and smear over the outer surface. As long as the water pressure is no more than a couple of feet of water, looks terrible but stops the leak for a few years

Denso tape (the commercial version) is much the same as the original "Sylglas". Nick's description is good, but be aware that it won't seal against very much hydrostatic pressure. In industry it is used to provide corrosion protection for buried steel pipe. Domestically, it was good for sealing broken roof glass in greenhouses and conservatories, also gutters, flashing, etc.

You may have seen online videos for (I think) wide PVC tape with a very thick gooey backing, these will seal against a bit more pressure. Actually ordinary electrical tape, stretched and tightly wound, will also seal against lower pressures, for example kitchen and bathroom waste pipes, and it would probably be ok on a copper "descender" from a cistern to a loo. But only if you can do several full turns, stretched. And only for splits or pinholes in the pipe, it won't usually work if the leak is at a compression fitting.

Sylglas, almost certainly.

Thanks. It doesn't appear to be stocked by any of the sheds, Screwfix, or Toolstation, though Amazon lists it:

That's the stuff. Although messy, it is comparatively easy to apply. You can cut it into convenient lengths and they will bond together.

(Plumbers epoxy resin sealant is good for some things, but needs more skill/experience to get it right).

I'd recommend wearing disposable latex or vinyl gloves!

It's the 90 degree bent pipe that connects the bottom of the cistern to the top rim of the toilet that seems to be leaking according to the OP. This happened to me. There is a special ?white rubber connector that fits over the spigot on the pan and the bent pipe coming from the cistern pushes into it and seals because it is tapered, from what I recollect.

Unscrewing the big plastic compression nut underneath the cistern is tricky. The plastic may have gone brittle over the years, so expect to have to replace the whole syphonic unit inside the cistern as well.

The foul connection (if properly installed originally) generally doesn't leak unless the joint has moved. I wonder if there has been a small leak for some time and the chipboard or flooring has been slowly damaged over the years ?.

Thanks, but it's not the foul connection that's leaking, it's the clean-water connection between the cistern and the loo.

Andrew laid this down on his screen :

Yep, that was what I had assumed and suggested a fix for.

That is just a cover, inside that and completely separate, will be the actual seal - which I described.

She needs a new flush pipe connector.

First get her to check that the flush pipe is not leaking at the cistern end, with the water running down.

Second, check the flush pipe is actually sitting correctly in the connector. Does she say water is gushing, or it's just a drip?

Third, get her to push the connector into the back of the loo. They can work loose.

The third option is the most likely one to work.

Lucky as that one can be dried off. I had one that wouldn't seal until I filled the polythene multi-disc sealer with silicone three times...

a standard diameter of pipe generally used for this purpose?

Sometimes the flush pipe tapers, so the vertical inlet and horizontal outlet are different diameters ...

When I had this problem, I just made the rubber boot fit really well. It got some stiff wire, looped it round and twisted the ends tight. It lasted years, and then we sold the house.

(it was 2.5mm insulated, out of a bit of cable)

It's generally no big deal to dismantle and replace that seal - unlike to foul water one?