Installing a sink waste

25 Jan 2004
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United Kingdom
I have a bathroom sink that I can't get the waste to seal into properly. It is a Wickes pedestal sink, and I am using the supplied 2-part pop-up waste.

It came with 2 washers and I tried using them with some genuine silicone, but it still leaks. So, I have taken the sink off the wall and removed the waste and silicone. Now to refit the waste!

Just to make sure I have got the right washers with my waste: there are two, both white rubber, identical. Not foam.

What I did was:

1) put loads of silicone in the contact area between waste and basin
2) slipped the first washer over the waste
3) pushed it through and moved it around a bit to get rid of air.
4) put a load of silicon on the underside of the basin, where the second part of the waste would contact it.
5) Then I slipped the washer over the underside of the waste where it poked through the basin
6) tightened the two halves together by hand, no spanner.

Now, I did it up what I thought to be quite tight, but it was only by hand as I didn't want to crack the sink.

Did I do this correctly? Should I have used a spanner? Are there enough washers?

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I'm not sure if silcone is the correct thing to use for sealing the waste outlet into the sink. I always thought that you used some sort of putty. Perhaps one of our plumbing experts could confirm?
At college we were taught to use plumbers mait for basin wastes.
Form a sausage and wrap around underside of waste (where metal meets porcelain) and fit in hole. Same on fitting thread protruding the hole, place plastic washer and then tighten nut. Remove excess from top and bottom and test.
I,ve only done a few but have found success with this method :)
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If you have no luck from anybody's suggestions, try a "basin waste seal 3 part set", it does not need any sealant costs about £3.00 and really does work. I've done about 6 with these and works first time every time.

Made by Dell Factor ltd, 01902 305111
Always used sanitary sealer silicone, I throw the washers away most of the time as they tend to bulge out when tightening because the silicone is slippy when wet, never had any problems, perhaps you need to tighten slightly with a spanner.
Thanks for all the advice, I now have several things to try just in case I can't get it to work first time! :LOL:

I had thought of plumbers mait, went down to Wickes and found their own brand says on it "not for use in bedding sink wastes", so thought I would try silicone again.

Fitter, where do you get this basin waste seal set from? I am hoping to buy one on Sunday morning so I would need to buy it from a shed rather than a merchant :confused:
I always use the evo-stik version of plumbers mait , I have just read the tub and it says you can use it for this purpose. Bahco is exactly right in it's method of use.

Do you think the home brand version may be inferior?
david and julie said:
Do you think the home brand version may be inferior?

Yes I do!

Getting to sheds from my way is a bit of a hassle, Wickes is the only one within a decent distance, and the merchants all close at 12 on Saturdays so it is a matter of convenience... Was thinking that if people have no preference for putty or sealant then it would be safe to try silicone again. :D But if people all said "use mait, much better" then I would make the pilgrimage to Homebase cos I know they sell it. :idea:
Adam, I get the kit from a local plumbing shop, I have not seen them in Wickes.

That's why I gave you the phone number, I thought you would have to phone them to get details of where you could get one locally.
Big tube silicone doesn't always work too well for that. Try using Fernox LS-X. Let it dry for more than 4 hours before running water.
First, you almost certainly do NOT have a bathroom sink - you have a basin! Not entirely being pedantic, the construction is different. The way all basins tend to leak is down the outside of the thread. If you look at all the washers they give you, there's nothing to stop water going down there. So thats where the silicone has to go on the lowermost nut/washer .
Above that the seal between the waste (metal bit) and the inside of the bowl, stops the bowl emptying but doesn't cause any leaks to outside the basin. I do not use plumbers mait or mate because I don't think its properties are suitable - except that it tends to stop the waste wobbling about while you're fiddling. The metal still does up against the ceramic. If there's ever any movement there the PM will unstick where it gets wet, until it eventually goes hard - then it'll crack. Silicone is far better, imho, though some of the foam washers are excellent.

The widgets referred to above certainly do work - they have a triangular section washer which compresses against the thread.
But without one of them, if you put the normal bottom washer on, run a finger of silicone round filling the gap between the washer and the thread (& above the washer first), then squash it by doing the nut up, it won't leak .
ChrisR said:
Not entirely being pedantic,

Pedantic is good, with knowledge comes pedantry! :D

I hadn't really considered the fact that the plughole can't cause a leak outside the sink, good stuff.

I am at my parents' house now, conveniently they had a new basin (not sink!) fitted last week so I have had a good look to figure out how their plumber did it. The first thing I noticed is that the plughole sits flush into the porcelain, i.e. there is no washer I can see and the nut must be done up tight to squeeze any silicone in there.

I'll see if I can find some Fernox LS-X and try Chris' method.

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