Leak under the kitchen sink: where the water comes from
First we turn the water off, then we find the exact point where it's escaping. In most cases it's the trap or a flexible hose (latiguillo), and the difference on the bill is huge. With a cloth, some kitchen roll and ten minutes, you'll know whether it's a case of tightening a nut or calling someone in.
Step 1 of 4
First things first: have you turned the water off?
Under the kitchen sink there are usually two small isolating valves (llaves de escuadra), one for cold and one for hot, right where the pipes up to the tap start. Turn them clockwise until they stop, without forcing them. If you can't find them or they won't turn, close the flat's main stopcock (llave de paso): it's usually in the bathroom, inside a kitchen cupboard or in the meter cupboard. Then empty the cupboard, take out the cleaning products and dry the bottom with kitchen roll. On a dry surface you can see where the water is coming from. On a two-day-old puddle, you can't see a thing.
The first step is always turning the water off
Before looking at anything, close the valves under the kitchen sink. There are two, one for cold water and one for hot, right where the pipes up to the tap start. Turn them clockwise until they stop. If you can't find them or they're seized, close the flat's main stopcock. Then empty the cupboard and dry the bottom: on a dry surface you can see where the water is coming from.
The five culprits behind nearly every leak under the sink
The trap is first on the list. It's the chunky plastic bend hanging under the plughole, and its nuts work loose by themselves over time. The flexible hoses run up to the tap; they hold constant pressure and give little warning before they burst. The concealed pipework leaks in the wall or in the body of the isolating valve, and those stains grow even when you don't use the sink. The dishwasher can leak inside or where its hose joins the waste, which are two very different problems. And then there's condensation, which isn't a leak even though it looks like one.
How to find the exact spot in ten minutes
Lay dry kitchen roll over the whole bottom of the cupboard and shine your phone torch upwards. Run the tap for a minute and see which piece of paper gets wet first. Then fill the sink right up and pull the plug all at once, because many waste leaks only appear when the pipe works under pressure. If you can't see anything, leave the paper another half hour.
What you can tighten yourself and what you can't
The wide plastic nuts on the trap are tightened by hand, no tools, until they stop. That fixes a lot of drips with no risk at all. What you shouldn't do is use a spanner or pliers on that plastic, because it strips its thread in two turns and then the trap won't seal however you try. Anything with a metal thread, the pipework in the wall, the isolating valve and the meter are off limits for home DIY: there, overtightening opens a worse leak than the original, with the water running. If the leak comes from the tap, what the market charges to replace one is in how much it costs to replace a tap.
What we do
Write to us on WhatsApp or through the form telling us what you found following these steps, with a photo of the trap from below if you can. We give you a fixed price in writing, usually in under two hours, and an independent professional who works with us comes to your home, a plumber by trade who works in your area. We cover Valencia city and the towns of l'Horta, and the price doesn't change during the job: if something else turns up, it's quoted separately and you decide.
Frequently asked questions
Can I tighten the trap nuts myself?
Yes, and it's one of the few things worth trying before calling anyone. Tighten them by hand until they stop, and stop there. Never with a spanner or pliers: the plastic strips its thread very quickly and then the trap won't seal, so you go from a small drip to having to replace the whole part.
How do I tell a leak from condensation?
Close the isolating valve, dry everything well and wait a few hours. If droplets appear again with the water off, it's condensation. Its appearance also gives it away: clean water with no smell, the whole pipe wet on the outside rather than one dripping point, and it shows up in summer and disappears in winter.
It only drips when I empty a full sink. Is that normal?
No, and it usually points to a blockage further down. When the pipe is full of grease the water doesn't flow freely, the pressure inside the trap rises and it escapes through the loosest seal. That's why you only see it when you empty the sink all at once. Replacing the trap without clearing the blockage fixes nothing.
I've used drain unblocker and nothing has changed. What do I do?
Stop pouring more in and tell us before the visit. If the pipe hasn't cleared, that product is still inside and whoever opens the trap will meet it all at once, so they need to know in advance and come protected. Repeating the dose three days running doesn't clear anything and can damage old pipes.