Leak under kitchen sink

[Palmist]

Hello Forum,

We have suspected a leak under kitchen sink for over 12 months, 2 different plumbers have been in, replaced a few valves and kitchen tap but the leak is still there. We know this as we keep a towel under and mysteriously it gets wet after a few days.

This morning I have found the culprit (at least one of them). I found a drop of water outside this metal nut highlighted in the picture. The metal nut seems to connect some kind of metal pressure valve to plastic plumbing, I turned the blue switch out of curiosity and there was a spray of water.

To be clear the leak seems to be on the metal gland nut not the blue plastic switch.

For now, I have put some tape and a bowl under, any advice on what it is and how to fix it will be very much appreciated.

 

[amfisted]

It’s an isolating valve, and it might be there to drain the pipework for maintenance purposes. Or maybe it’s a redundant connection to a removed appliance. In any case, that kind of leak can sometimes be cured simply by tightening the leaking nut. Take two adjustable spanners, use one to hold the left hand nut and prevent it from moving, put a second spanner on the leaking nut and tighten it clockwise ( away from you) about one eighth of a turn. If it won’t move, don’t force it. If the leak dries out, great. If not then you could try another turn, but don’t overtighten because you could make it worse. If that doesn’t work, and being someone with little experience of joining plastic to metal, I’ll defer to other forum members for the next stage in the process.

 

[Elkato531]

Looks like a redundant fitting which could be removed. I would also get the bodged up sink waste replaced as this is also likely to be a leak source. Fitting a good quality sink waste/trap correctly is not difficult but I've always been amazed at how many are done badly even by professionals. Many seem not to have even grasped the idea that water does not flow up hill

 

[dilalio]

It's a washing machine valve.
It's not in use.
It should be capped I case the handle gets knocked.
They often fail and leak at the handle.
The speedfit tee which leads to it needs the collet tightening as not in the locked position.

 

[Palmist]

Thanks, is capping a diy job?

 

[Palmist]

Thanks, I will give this a go, there seems to be a little leak from the copper end also, which as mentioned in another post needs to be capped.

 

[dilalio]

Thanks, is capping a diy job?

Yep. Simple. I use brass caps with rubber washer but Toolstation do a plastic one for about the same price... Likely cheaper in your local independent merchants.

Google Search

 

[Palmist]

I have fitted the cap and tightened the valve as suggested but the leak continued so I spend some time just watching it and the leak is actually happening much higher, the water drops hit the valves on way making it look like they are the culprit.

The leak is happening at counter level, any splash from washing dishes or using the sink which gathers around the tap base as shown in photos then makes it way to under the sink.

I had this tap fitted last September and the leak has always been there, we have just been replacing towels. I have contacted the plumber who installed this tap.

 

[Elkato531]

Looks more like it may be leaking through where the sink seals against the underside of the worktop.

 

[Scally-Ho]

Yes, I agree with you @Elkato531 that looks to be the culprit.

@Palmist Your under mounted metal sink has most probably flexed and broken the all important seal against your work top. The only way to stop that leak is to remove the sink and after a thorough cleaning refix it with a good sealant, AND allow good time before using it again. Personally, I much prefer top mounted sinks and drainers because the rigidity of the worktop stops any flexing of the sink.

 

[Palmist]

Thanks, plumber booked in for next week, till then we just have to be careful. I am a bit kicking myself for letting this carry on for almost 14 months.

Really appreciate all the help and advice from this group.

 

[dilalio]

Just run a bead of clear silicone around the sink where it meets the worktop.

Simples.

 

[dilalio]

Top tip... Plumbers know to always check above where a leak is noticed!

I've found the source 2 floors up from where it's first noticed and 5 metres away when it's through a ceiling!

 

[Elkato531]

Just run a bead of clear silicone around the sink where it meets the worktop.

Simples.

That's what I'd do.

 

[ree]

Why not remove the sink and the - clean everything above & below the work top, and re-install it correctly because if its not correctly installed then it will surely leak again. As above, the weight of water & dishes etc will weigh it down & open it up.
Correctly means a continuous bead of fixing silicone & any using any c/w clips - then another sealing bead of silicone thats smoothed into one continuous bead (as above advised) not bits of dabs as it is now.
Remove & clean up the mixer - change the washer.

FWIW: no plumber did that under sink installation, & if a plumber coming then why not let the plumber sort out all the under sink - trap & hoses etc - shaky looking arrangement?