You open the cabinet under the sink to grab a trash bag… and bam. That weird smell. A small puddle. Slightly sticky, slightly cold on your fingers. Honestly, a leak under the sink is one of those home problems nobody plans for, but almost everyone gets at some point. And the worst part ? It almost never starts as a disaster. It starts small. A drip. Then two. Then one day your chipboard cabinet is swollen like a sponge.
Second thing I always tell people : don’t panic, and don’t call a plumber right away. In most cases, you can at least identify what’s going on yourself. If you like practical DIY content, I sometimes peek at https://bricolage-joyeux.fr for ideas and reminders. It helps put things into perspective. Most under-sink leaks are basic, really basic.
Where does the water usually come from ?
Let’s be clear : water doesn’t magically appear under your sink. It follows gravity. So if there’s a puddle, something above it is leaking. The tricky part is figuring out what.
Most of the time, it’s one of these :
The siphon. Classic. Plastic, cheap, easy to unscrew. A badly tightened ring, a cracked joint, or a siphon slightly bumped while storing cleaning products. I’ve seen it so many times. You move one bottle, and suddenly it drips.
The drain connection. Where the sink meets the pipe. That rubber seal gets tired. It dries, shrinks, and stops sealing properly. You don’t see it at first, then one day it decides it’s done.
The water supply hoses. Less common, but more annoying. Those flexible hoses feeding hot and cold water can sweat, loosen, or leak at the nut. Touch them with a dry finger. Wet ? There’s your culprit.
The faucet base. This one surprised me the first time. The leak doesn’t show on top, but water runs down under the sink. Sneaky.
How to spot the exact cause (without special tools)
You don’t need fancy gear. Just patience, a dry cloth, and maybe a flashlight.
First, dry everything. Really dry. Wipe pipes, siphon, cabinet floor. Then open the tap and watch. Yes, like you’re watching paint dry. It works.
Ask yourself : does it leak only when water runs ? Or even when everything is off ? That detail matters a lot.
If it leaks only when draining, the siphon or drain is guilty. If it leaks even with taps closed, look at the supply hoses. Simple logic, but people skip it.
And don’t rush. Sometimes it takes 30 seconds before the first drop appears. Annoying, but worth it.
Fixing it yourself : honestly, it’s doable
I know, “plumbing” sounds scary. But under-sink plumbing is the kindergarten level of the trade.
Tightening connections
Start here. Hand-tight first. No Hulk strength. Plastic breaks fast. If needed, a quarter turn with pliers, gently.
Replacing a joint
If you see a flat rubber gasket that looks crushed or cracked, replace it. These things cost a few dollars. Bring the old one to the store. Trust me, guessing the size never works.
Changing the siphon
Sometimes it’s just not worth fighting old plastic. A new siphon is cheap, and installing it takes 10 minutes. I’ve done it half-asleep on a Sunday morning. Align it properly, tighten evenly, done.
Supply hose issues
This one needs a bit more care. Shut off the water first. Always. If the hose itself leaks, replace it. Don’t patch it. Ever. That’s asking for a flood at 3 a.m.
Common mistakes that make things worse
Overtightening. Big classic. You think tighter means safer. Nope. It means cracked threads.
Ignoring “just a drip”. That drip can soak wood slowly. I’ve seen cabinets ruined over a leak that could’ve been fixed in five minutes.
Using sealant everywhere. Silicone is not magic. If a joint needs silicone to stop leaking, something else is wrong.
When you should stop and call a pro
Let’s be honest. Sometimes DIY hits a wall.
If the leak comes from inside the wall.
If pipes are corroded metal and crumble when touched.
If you shut off the water and it still leaks (yeah, scary).
In those cases, calling a plumber is not weakness. It’s common sense.
Final thought (from experience)
A leak under the sink is annoying, a bit stressful, and honestly kind of gross. But it’s also one of the most fixable home problems out there. The key is acting early. The earlier you deal with it, the cheaper, cleaner, and calmer it stays.
So next time you smell humidity under your sink, ask yourself : do I really want to deal with this later… or fix it now in 20 minutes ?