Slight leak behind WC bowl

[Timothy Murphy]

I have a very slight leak - maybe 4 drops a day - behind my WC, where the waste-pipe attaches to the bowl.

I'm wondering if it is possible to seal this, eg with silicone, without dismantling the joint?

[Slider]

Is it definitely a leak and not just condensation?

[Tim S]

Timothy Murphy coughed up some electrons that declared:

Is it definately the waste pipe and not the flush coupling? I had the same problem and I thought the same as you, until I looked really closely - and it turned out to the the cistern pipe to bowl seal was dodgey. The water was dripping down onto the waste pipe then off that onto the floor.

In any case, stuffing it with silicone should be fine for such a tiny leak - there's little pressure. It's best if you can get the silicon to go into a recess rather than smearing it over the surface, if possible.

Obviously, ensure the area is degreased and clean and dry before applying and leave it for enough time to go off before using the loo.

Cheers

Tim

[Lobster]

I remember somebody on here advocating pouring PVA glue solution into the toilet bowl overnight, to cure a very slow leak like this with miniumum aggro. Never tried it myself but it may be worth a try!

david

[Timothy Murphy]

Thanks for the suggestion. I'll check that.

[Timothy Murphy]

Sounds interesting ... I wonder if anyone can endorse this suggestion?

[John]

How does the waste pipe attach to the bowl - is it a plastic Multiwik collar?

so, and you are sure this is leaking and not the flush as suggested, then if you feel slightly brave I would give it a wiggle and a twist to try to re-seat it.

[Toom Tabard]

Yes, just squeeze some Plumbers Mait non-setting putty into any gap(s) around the joint.

Toom

[The Medway Handyman]

Wonderful stuff! Used some this very afternoon for exactly that problem.

[Rod]

And I have used some FT101 for just that purpose. I wouldn't use Plumbers' Mait for that as it doesn't IMHO have the flexibility required.

[The Medway Handyman]

But its non setting, so it must remain flexible. Isn't that its benefit?

[Timothy Murphy]

Yes, I'm almost certain that is what the plumber used 25 years ago.

Thanks for the suggestion. I'll check the flush and if it's not that I'll try what you suggest.

[Rod]

IME it's a bit like window putty - it firms up quite a lot. Get into an old PM joint and it still won't be hard - but it sure ain't soft and flexible. Sufficient for the gap between two nice hard things like copper and heavy lead or ceramic. But not plastics and rubber.

Plus, it certainly used to affect plastics - seems to make them deteriorate, albeit quiet slowly. Can't really remember, but didn't it say something of the sort on the tin?

[The Natural Philosopher]

Yes.

[Toom Tabard]

I used Plumbers Mait to seal the rubber flange gasket where the cistern inlet pipe goes into the ceramic toilet bowl. That was fifteen years ago. It was still sealing it, and soft and flexible, when I installed a new toilet bowl several weeks ago. And I was able to wipe it off and re-use the gasket without it since the new toilet pan inlet seemed a better fit for the gasket .And it is still after fifteen years sealing the gasket in the joint/overlap between the plastic outlet pipe and the metal drain pipe. If, rather than just plugging a gap as a precaution, it's actually stopping a low pressure leak, then I think the leak it's stopping also keeps it soft, if you see what I mean. Anyway, either way, it seems to work long term.

Toom

[John]

Several contributors have suggested some sort of sealant to be applied. I respectfully suggest this is not such a good idea as it will only trap nasty water between each lip of the Multiwik seal as each will progressively fill up. At less than a fiver (I think - and if it is within the scope of the OP then I would suggest replacing it as it may have been distorted - or be damaged. I believe they are usually very reliable - ideally the first ring of seals should stop the leak - subsequent ones are for insurance! If you apply gunge behind the Multiwik then the whole thing traps water within it.

[Timothy Murphy]

As the OP, I could afford a new Multiwik, but I could not afford my wife's reaction if my "improvement" disimproved things.

[Rod]

The awkwardness of replacing the rubber thing would have been unwelcome. The joint between the downpipe and the cistern is solid and sound - and I do not wish to dismantle.

[John]

I think you will be delaying the problem rather than fixing it - after all no-one would suggest trying to fix a leaking compression joint by pasting stuff on the outside. I realise the pressures are different - but you are trapping foul water inside the seal - it don't seem right!

[Rod]

Don't think there is much space between the fins - I tried to fill it as much as possible. You might be right - but I shall deal with it if it occurs.