Pipe/waste leak under kitchen sink - how to fix?

DIYhelp76

Hi,
Hope someone can help. We have discovered water slow leaking under kitchen sink.  I will attach photos.  It seems to come from the seal under the sink waste.  It looks rusty, even though the fitting itself seems plastic.  Could there be a metal washer even though it looks plastic?  There is silicone around it but it still leaks.
What is best/correct way to fix this?  We aren't plumbers!  As an alternative, would scraping off rusty substance, spraying WD40 and adding more silicone work?
Many thanks!

DIYhelp76

Photos showing the leak

Martin_the_Unjust

https://www.wickes.co.uk/how-to-guides/kitchens/how-to-fix-leaking-sink

Explains it better than I can.

grumpy_codger

DIYhelp76 said:

...
What is best/correct way to fix this?  We aren't plumbers!  

The correct way is to disassemble the waste, check what's wrong with the rubber seal under the sink (between the sink and the waste) and, possibly, replace the seal. The screw holding the waste is at the top.

As an alternative, would scraping off rusty substance, spraying WD40 and adding more silicone work?

No chance. WD is absolutely wrong product in this case. Silicon can be added, but only on the rubber washer when assembling the waste back after you disassembled it first.

vacheron

This seal looks like it may need replaced, but first try to tighten the screw in the middle of the sink plug as shown in the Wickes guide posted by Martin_the_Unjust above just in case it has worked loose. Do not try to overtighten if it already feels snug though, as this could make things a lot worse! 

This could stop any leaking for now. 

If this doesn't work, waste disassembly (by undoing the same screw), followed by cleaning (or replacement) as necesary as grumpy_codger mentioned above.

WIAWSNB

Not sure what that brown gunk is, but it's almost certainly not rust. So don't treat anything as if it could be.
Has anyone ID'd the make? There's a logo visible in a photo. A new sink waste section might be worthwhile - they ain't expensive, prob around £10.

chrisw

It looks like very slow leak over a very long period of time. If the screw is not loose and it's not running down and dripping on to the shelf or whatever below it, you could just give it a wipe over and leave it.

DIYhelp76

Hi all, many thanks for the helpful replies.  Yes it's definitely been going on a long time and is slow - not a lot of water, but enough to be a nuisance with things stored under the sink. Initially thought it was the spare overflow (not in use and without blanking plug) - but added blanking plug a while back and it's still leaking. 

The "rust" coloured gunk is weird, because if the washers are rubber they can't "rust" like this.  It is an Ikea butler style sink, about 15 years old.  Cannot remember whether the plumber who fitted it used the ikea waste kit that must have come with the sink, or if he bought his own?  I can try unscrewing it, but first issue is it's not a normal style screw in the waste, it is a weird big hole with two kind of slots on either side. Not sure if it needs a special tool to undo this?  Also, I'm guessing it won't come away freely due to all the silicone underneath?

Once I can unscrew it and look, if new washers should these be a standard size and should silicone be put on the undersides and then around the outside of the under sink one, as looks to have been done before.  Bit worried I might make it leak a whole lot more 

grumpy_codger

DIYhelp76 said:

...I can try unscrewing it, but first issue is it's not a normal style screw in the waste, it is a weird big hole with two kind of slots on either side. Not sure if it needs a special tool to undo this? 

See my picture above? It explains the 'big hole'. You just need a flat screwdriver big enough to get into both slots at the same time. You can try a coin and pliers but take care not to damage the slots.

Also, I'm guessing it won't come away freely due to all the silicone underneath?

Ordinary silicone is sealant, not  glue/adhesive.

Once I can unscrew it and look, if new washers should these be a standard size and should silicone be put on the undersides and then around the outside of the under sink one, as looks to have been done before. 

You clean the sink, the washer and the waste, then smear the flat top and bottom surfaces of the washer with some silicone to seal the possible gaps between the sink, the washer and the waste. Good elastic washer doesn't need any silicone for this. What was done before - silicone around - was a bodge.

diveunderthebonnet

DIYhelp76 said:

Hi all, many thanks for the helpful replies.  Yes it's definitely been going on a long time and is slow - not a lot of water, but enough to be a nuisance with things stored under the sink. Initially thought it was the spare overflow (not in use and without blanking plug) - but added blanking plug a while back and it's still leaking. 

The "rust" coloured gunk is weird, because if the washers are rubber they can't "rust" like this.  It is an Ikea butler style sink, about 15 years old.  Cannot remember whether the plumber who fitted it used the ikea waste kit that must have come with the sink, or if he bought his own?  I can try unscrewing it, but first issue is it's not a normal style screw in the waste, it is a weird big hole with two kind of slots on either side. Not sure if it needs a special tool to undo this?  Also, I'm guessing it won't come away freely due to all the silicone underneath?

Once I can unscrew it and look, if new washers should these be a standard size and should silicone be put on the undersides and then around the outside of the under sink one, as looks to have been done before.  Bit worried I might make it leak a whole lot more 

Can you post a photo of the screw? as for when you repair it ,empty the shelf under the leaking fitting ,place a bucket under it ,disconnect the fittings on either side and retain the sealing washers ,remove the special screw and drop down the leaking waste ,clean it up and check the sealing washer ,if perished a new one can e bought from B and Q, Screwfix etc. or a complete waste pipe from the previous outlets ,when refitting SMEAR A THIN COAT OF SILICONE ON BOTH SIDES OF THE WASHER ,refi and tighten up but just nip up the screw ,leave for about an hour and then tighten up fully.
Job done.

WIAWSNB

Have you managed to find something thin and wide enough to span the wee central hole and catch the slots either side in order to let you unscrew the waste?
If so, first try tightening it a small amount, literally an eighth turn. Does it turn? If so, how did it fell - was it quite firm, and became more so; did it 'feel' as tho it was 'tightening'?
If so, then good chance that will have stopped the drip - you could leave it like that if you wanted, tho' best to dismantle, clean, and reassemble.
But if the screw doesn't budge as you try and tighten it, then the thread may be at its max, so good chance the waste has been distorted, and worth considering a replacement. I'll try and ID the make - these parts are cheap, but you ideally want the exact same as they can vary in 'drop'.
No harm at all in you dismantling it all and giving it a good clean - you cannot mess up by doing this, it'll be very satisfying, and worst case is that you need to replace it.