Leak of handbasin waste after reassembly

The pedestal hand basin in the bath room had come away from the wall.

As part of the fix (which of course involved dismantling the basin , tap connectors , pedestal to make good the fixing holes) I decided to install isolating valves in the vertical supply pipes and generally clean out the sink components, remove old sealant ect .

This is the first time I have attacked this basin . I am dealing with an inherited installation.

This job has generally gone to plan but I have a problem with a leak of the waste outlet as it comes out immediately under the sink. It is clear that water is leaking between the plug hole body and the body of the sink.

When I dismantled the waste outlet as part of the job I found a low profile

8 sided plastic nut bolting the waste outlet to the underside of the sink. Pretty standard I think. This gripped a large ( oversize to the external dimensions of the 8 sided nut ) plastic "washer " between the nut and the sink body. Not sure this is standard it looked like a bit of improvisation on the part of the installer.

On the inside of the sink there was no seal or washer between the outlet flange and the sink body. Instead ( I was surprised but perhaps that is my ignorance) the was a bed of plumbers mate and this was also packed between the thread of the outlet and the waste hole of the basin.

When I reassembled I used the same 8 sided nut and oversize washer. On the inside I did not use plumbers mate ( although I have some , used it to bed the basin on the pedestal) instead I used an appropriately sized plastic seal ring ( white , clear ish , from B & Q "sundries" pack of various sizes).

I did worry that I had perhaps not been able to tighten the 8 sided nut firmly enough ( because the very low profile) prevented a good grip with adjustable spanner , stillson etc. Sure enough when all was back in place there was a serious leak around the waste outlet.

I wondered about the tightness of the nut , but also my seal washer in place of plumbers mate ( even though I have never understood the later is used to provide for watertight situations. I think of it as bedding and gap filling material).

I went out to B & Q tonight intending to find an appropriate sized "ring " spanner for the out let nut. There appeared to be no such thing. In stead I purchased a new bog standard waste outlet. A straight replacement except that this had a much chunkier nut with a taller profile. I fancied that I could get a decent grip on that. The out let came with plastic or rubber seal for inside the basin to seat the outlet. It seemed more rubbery than the one I had used earlier so that was a good sign. There was no equivalent of the large washer /sealer between the nut and the underbody of the basin.

Have just taken the sink off again and fitted the new outlet. My tools got a good grip on the nut and with the new outlet thread I thought I had solved the problem. There is a 90% improvement but there is still a noticeable (although less dramatic ) leak . Again it is definitely coming from between the basin body and the outlet.

I thought I had tightened the nut as tight as was safe , maybe not . Or should I be using plumbers mate under the outlet flange ? Should there be a sealer / washer between the nut and the underside of the basin ?

Any ideas / comment for when I try again tomorrow. At least in the circumstances I am particularly glad I fitted those isolation valves. !

Thanks

Richard

Reply to
Jack Fate
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I always use clear silicone sanitary sealant in the circumstances you describe, on outlets from sinks and toilet cisterns.

Reply to
DIY

Thanks . Presumably that is applied on the inside of the basin ? Do you use it as a "bed" layer between the washer and the basin or between the washer and the flange ? or perhaps it replaces the washer ?

Richard

Reply to
Jack Fate

I had a similar problem. My sink came away from the wall so I decided to change the waste trap while I was at it as I thought it was producing a strange smell.

On reconnecting everything (using plumbers mait) everything was water tight. Screwed it back on the wall and then a few hours later noticed there was a wet patch below it. Removed everything again, cleaned it all up and tried a bead of silicone (as recommended on here) under the flange of the waste that rests on the basin. Again everything water tight. screwed it back on the wall and the bloody thing leaked again!!!

Turns out as I was screwing the sink back on the wall, it was making the waste pipe/ trap / sink waste sit at an angle thus unsealing the joints. Ended up putting washers between the screws and the wall to make the sink stand out slightly which cured the problem.

But to answer your question, I would definitely put plmbers mait between the basin and the sink waste.

Reply to
Tony

That's your problem! I always use a ring of PM between the basin and waste flange, then for good measure I put another ring on the underside where the waste thread exits the basin hole then put the plastic washer over the PM and tighten everything up and all is Hunky Chunky!

HTH

John

Reply to
John

I would probably get rid of the washer and just do a good bead of silicone. In fact for sanitary fittings I always use loads of silicone between all mating surfaces, i.e. a bead of it between the top of the waste and the sink, a bead of it between the bottom of the sink and the washer then a bead between the bottom of the washer and the top of the hexagonal nut. Then tighten the whole thing up and wipe away any excess. I've done this loads of time on these kind of fittings and never had a leak - the silicone dries into a kind of perfectly fitting washer.

Reply to
Richard Conway

I apply clear silicone sanitary sealant to each and every surface past which water could possibly leak.

Reply to
DIY

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