Most Common Sink Problems: Slow Draining, Leaking, or Smelling

Common Sink Problems: Match the Symptom to the Cause

Most sink problems announce themselves before they turn into a repair bill. A slow drain, a puddle in the cabinet, and a gurgle after the washer runs are three different problems with three different fixes, even though they all look like “something is wrong with the sink.”

Start here. Find what your sink is doing in the left column, then read the section below for what is causing it.

What you see or hear	Most likely cause
One sink drains slowly, the rest of the house is fine	Clog in that sink’s P-trap or tailpiece
Every drain in the house is slow	Main line problem, not a sink problem
Water pools in the cabinet under the sink	Loose slip nut, failed trap washer, or supply line drip
Ring of water around the base of the faucet	Failed faucet base gasket or loose mounting nut
Drip from the spout that will not stop	Worn cartridge or washer inside the faucet
Gurgling when the washer or dishwasher drains	Venting problem or partial main line clog
Sewer smell coming from the sink	Dry P-trap or failed trap seal
Water backs up into the other basin	Clog downstream of the tee, past both basins
Faucet pressure dropped on one side only	Clogged aerator or a partly closed angle stop
Stain or soft spot on the cabinet floor	Slow leak that has been running a while
Rust colored ring in the basin that returns	Iron in the water, not a sink defect
Hairline crack in the basin itself	Age, impact, or thermal shock

Sink Problem or Drain Problem? The Test That Tells You in 60 Seconds

This is the single most useful thing on this page, because it tells you whether the problem stops at that one sink or sits in the drain system behind it. Those are two different repairs.

Fill the sink about a third of the way, then pull the stopper and watch.

Water leaves fast, then the last bit crawls. That points at the P-trap, the curved pipe under the basin. Debris settles in the bend. This is the most common sink problem we see and it is usually a clean-out, not a repair.
Water leaves slowly the whole way down, at the same steady crawl. The restriction is further down the branch line, past the trap. A plunger will not reach it.
Water barely moves, and you hear air bubbling back up. Air is being pulled from somewhere it should not be. That is a venting or main line issue, and the sink is only where you happen to be noticing it.
Water drains fine, but comes back up when another fixture runs. The sink is healthy. Something shared downstream is restricted. A dishwasher or washing machine pumps out several gallons in seconds, far more than a running faucet, and a partly blocked line cannot move that much at once. It surfaces at the nearest opening, which is your sink.

Only the first bullet is a sink problem in the strict sense. The other three point past it, at the branch line, the vent, or the main, and clearing the basin will not solve any of them. Knowing which one you are looking at is worth telling us when you call, because it changes what we bring and how long the visit takes.

Why Is My Kitchen Sink Draining Slowly?

A kitchen sink that drains slowly is almost always grease, even in a home where nobody pours grease down the drain on purpose. It comes off dishes, pans, and plates in small amounts every single day. Warm water carries it a few feet down the pipe, then it cools, sticks to the pipe wall, and starts catching everything else that comes through.

What actually clears it:

The P-trap gets opened and cleaned out. Most of the time the grease is sitting right in the bend under the basin. It comes off the pipe wall, the slip nut washers get checked while the trap is apart, and the joints get reseated so they do not weep afterward. That last part is where a lot of under-sink leaks start.
If the trap is clean, the branch line gets cleared. Grease coats the whole pipe, not just the bend, so punching a hole through it buys a few weeks. Scouring the pipe wall is what makes it last.

What keeps it from coming back is habit, not tools: scrape plates into the trash instead of the basin, keep cooking grease out of the drain entirely, and run hot water for a minute after you cook.

Do Chemical Drain Cleaners Work on a Kitchen Sink?

What we would skip: chemical drain openers. They generate heat, they rarely clear a full grease clog, and if they sit in the line without clearing it, the next person to open that trap gets a face full of caustic liquid. The U.S. Consumer Product Safety Commission treats them as household hazards for good reason. On older metal traps they can also eat the pipe.

If the trap comes back clean and the sink still crawls, the clog is further down the branch line. We can snake the branch line, and for repeat kitchen clogs we can hydro jet the line to scour the grease off the pipe wall instead of just punching a hole through it. For a drain that keeps coming back, we can also run a camera, which is usually how we find the actual reason.

Why Is My Bathroom Sink Draining Slowly?

Bathroom sinks clog with hair and soap scum, and they almost always clog at the pop-up stopper rather than in the trap. The stopper has a small crossbar behind it that catches hair by design.

That is why cleaner poured down a slow bathroom sink does so little. The blockage is not down in the trap where the cleaner ends up. It is wrapped around the stopper crossbar a few inches below the drain, and the stopper only comes out once the pivot rod behind the drain body is released. What comes up with it is usually the entire problem.

South Florida water adds a second layer here. Our water is hard, roughly two to three times harder than the national average according to USGS hardness mapping, so soap does not fully rinse away. It combines with the minerals and leaves a sticky film on the pipe wall that hair grabs onto. That is why the same bathroom sink clogs again three months later even though you cleaned it properly.

Why Is There Water Under My Sink?

Water under a sink usually comes from one of four places: the supply lines, the drain assembly, the faucet base, or the sink rim. This is one of the few sink problems you can narrow down by observation alone, and a puddle in the cabinet is worth finding fast, because the cabinet floor is usually particleboard and it does not recover. Dry everything completely, lay down a sheet of paper towel, and then test one thing at a time.

Supply lines. Run nothing. Wait an hour. If the towel is wet, it is a supply side leak, since those are under pressure all the time. That is the kind we chase with leak detection when the source is not obvious. Check the braided lines and the angle stops behind them.
The drain assembly. Fill the basin, then release it all at once. A trap or slip nut leak shows up only when a real volume of water passes through.
The faucet base. Run the faucet hard for thirty seconds and feel underneath where the faucet bolts through the counter. Water tracking down the mounting shank means the base gasket has failed.
The sink rim. Splash water around the edge of the basin where it meets the counter. If it shows up below, the rim caulk or the sink clips have let go.

Whichever one it turns out to be, note it down before you call. Telling us the water only shows up when the basin drains, or that it drips with everything shut off, narrows the repair down before a truck is even loaded.

Why Does My Sink Smell Like Sewer?

A sewer smell coming out of a sink almost always means the P-trap has lost its water seal. Under every sink there is a curved piece of pipe called a P-trap, and it holds a small amount of standing water at all times. That water works like a plug. It is the only thing keeping the smell inside the drain pipes from drifting back up into the room. When the trap dries out, the plug goes with it and the smell comes straight up.

This is common in guest bathrooms, second homes, and seasonal condos where a sink goes unused for weeks. Running the water for thirty seconds refills the seal, and the smell goes with it. No repair needed.

If the sink is used daily and still smells, the trap is not the problem. The garbage disposal splash guard is the usual second source, because food packs underneath the flaps where nothing rinses it away. If the smell survives both of those, the trap seal may be siphoning out through a venting problem, and that needs a licensed plumber.

Why Does My Faucet Drip When It Is Turned Off?

A steady drip is almost always a worn cartridge. Modern faucets use a replaceable cartridge instead of the old rubber washers, and they are consumable parts with a service life.

Worth doing, because a drip is more than annoying. The EPA puts a faucet dripping once per second at about 3,000 gallons a year.

The aerator at the tip of the spout is worth ruling out first. Hard water mineralizes those screens constantly here, and a blocked aerator can mimic both a pressure drop and a dribble after shutoff, so a faucet that seems worn out is sometimes only restricted at the very end.

Cartridges are brand and model specific, and one that has been in service for years often seizes in the faucet body, which is how a small part turns into a replaced faucet. We identify the cartridge, replace it, and test the valve under pressure before we leave. Note that we repair and replace sink fixtures, valves, and trim. We do not do countertop or cabinet work, so if the sink itself is coming out as part of a remodel, that is a different trade.

When Should You Call a Plumber for a Sink Problem?

Call rather than wait when:

More than one fixture is slow. That is a shared line, and the sink is a symptom.
You hear gurgling from a different fixture when the sink or an appliance drains. That points at venting or the main.
The same sink has clogged three times in a year. Repeat clogs in one spot usually mean something structural, like a belly in the line, a bad slope, or roots. A camera inspection answers it in one visit.
There is a soft spot or dark stain on the cabinet floor. That leak has been running long enough to soak in, and the fix is now more than a washer. Leak detection finds the source without opening the whole cabinet.
Water is showing up and you cannot find where it starts. A leak behind the cabinet wall or under the sink base can run for weeks before it surfaces, and the cabinet floor and drywall take it first.

If you have a Total Home Service Warranty, most sink problems and drain calls are covered with no trip fee and no service charge. Without one, call or text (954) 454-6801 or request service online. Water that is actively running and will not shut off at the angle stop is an emergency plumbing call.

Sink Problems FAQ

Diagnosing Common Sink Problems

What are the most common sink problems?

The most common sink problems are a slow draining basin, water pooling in the cabinet underneath, a sewer smell coming up the drain, and a faucet that drips when it is turned off. A slow kitchen sink is usually grease built up in the P-trap. A slow bathroom sink is usually hair caught on the pop-up stopper rather than down in the trap.

How do I know if it is my sink or the main drain line?

Fill the sink a third of the way and release it. If water drains fast and only the last bit crawls, the problem is in that sink’s P-trap. If every drain in the house is slow, or you hear gurgling from another fixture, the problem is downstream and clearing the sink will not help.

Why does my sink back up when the dishwasher runs?

The dishwasher drains into the same line as the kitchen sink and pumps out several gallons in a few seconds. A partly blocked line passes a running faucet fine but cannot move that much water at once, so it backs up at the nearest opening, which is the sink basin. The dishwasher is working correctly. It is only moving enough water to expose a restriction that is already there.

Drain Cleaners, Repeat Clogs, and Coverage

Why does my sink keep clogging even after I clean it?

South Florida water is roughly two to three times harder than the national average, so soap and grease leave a sticky film on the pipe wall that catches debris. Cleaning the trap removes the blockage but not the film. Repeat clogs in the same spot can also indicate a slope problem or a belly in the line, which a camera inspection can confirm.

Should I use chemical drain cleaner on a slow sink?

We do not recommend it. Chemical openers rarely clear a full grease clog, they can damage older metal traps, and if they sit in the line they create a hazard for whoever opens the trap next. Having the trap opened and cleared properly is both more effective and safer.

Does Total cover sink repair under a home service warranty?

Most sink and drain service calls are covered under a Total Home Service Warranty with no trip fee and no service charge. Coverage details depend on your specific plan.