Help! Leak inside kitchen unit.

Check it's a Flat Faced Male Straight Isolating Valve 15mm.

Some use standard isolation valve ment for pipe and it's not flat faced. The sharp edge digs in the rubber washer causing a leak. (edited)

I believe you'll need a new flexi pipe and valve installed, they usually start to leak like this over time.

A plumber should be able to sort this out within an hour.

If the leak gets worse before you can fix it, simply turn the screw in the valve to the off position and that will stop flow of water.

Personally I would try tightening up the nut using two sets of pliers (one to hold the valve in place and other to tighten the nut).
Its likely the flexi pipe may need replacing due to worn out washer but it's worth tightening first especially as water can easily be isolated by the valve.

Casual observation:
also consider that a minor liquid leak will flow / drip at the lowest point, meaning the source of the leak may not be at the nearest joint to the physical drip.

quite likely as wayners suggests, the flexible tap connector has been bolted onto the end of a standard isolation valve (like the one pictured below) which has had its olive and compression nut removed. The ends taper to compress the olive and if misused this way will cut into the washer in the flexible pipe.


If that's the case. either replace it with a flat faced isolating valve designed for the job (which should fit onto the existing nut), or find a spare nut and olive and add an adaptor:-


The rubber washer will probably need changing, and if it doesn't come out get a new flexible connector.

I would also find and check that the stopcock works first in case the plumber used poor quality isolating valves which can start leaking around the screw when they are turned off. I got a load from screwfix that did that, and also had to replace one a plumber installed in our airing cupboard which the screw popped inside, letting water spurt out the first time I turned it off. (edited)

Escalated to flood and insurance claim by now.

Probably needs the washer replaced in the silver braided connection

Loads of vids on YouTube

I think think them flexible hoses have olive (rings) in the nut then when compressed they seal. Turn water supply off and tighten the bolt turn water supply on an see if still dripping!

First thing turn the flat head screw in the middle 90 degrees. That stops the water flowing to where the leak is. The flow is left to right on your photo. From there, with something under it, you can investigate (edited)

Tap connector
screwfix.com/c/heating-plumbing/flexible-hoses/cat831572?cm_sp=managedredirect-_-plumbing-_-flexiblehoses

Might just be a perished washer

screwfix.com/p/arctic-products-flexible-tap-connector-washers-1-2-10-pack/2035j (edited)

Thanks lots valuable information.
I'll start investigating and update you how I go.

Probably find its the actual small screw valve that's leaking and water travelled to that point prior to dripping.

Change these out for ball bearing based isolation valve

Still leaking then