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Help! How Do I Stop My Bathroom Sink Leaking?

If you're dealing with a bathroom sink leaking on the floor or inside your sink cabinet, you've come to the right post.

When you see a pool of water on the bathroom floor by the cabinet or inside the bathroom cabinet, it's certainly not a good discovery. A leaking bathroom sink can be a small problem and sometimes simply to fix, but if left untreated can lead to a major plumbing repair, serious property damage, and health risks.

In this guide, we'll help answer some of the most common questions our local plumbers hear from customers dealing with a bathroom sink drain leaking:

  • Why is my bathroom sink leaking?
  • Where is the leak under my bathroom sink coming from?
  • How do I fix sink leaking pipes?
  • Are sink leaks in my bathroom dangerous?

Is a Bathroom Sink Leaking Dangerous?

Yes! A leak in the bathroom sink might be more serious than a leak elsewhere. For example, if there is a locked vanity concealing the drain, leaks might go unnoticed for a long time. This can lead to water damage and potential mold growth.

Because the sink leaks only when it is used, there is no continuous flow that would form a visible puddle. Rather than relying on the vanity or floor wood, which might soak up the water. The wood rots with time, and the humidity level in the bathroom rises significantly.

If the odor is overpowering in a bathroom, it indicates that mold may be growing in an obscure or inconspicuous location. And this is a common sign that you have a leak.

Understanding Your Bathroom Sink Drain Assembly

Every sink is unique, and what you'll find in the bathroom is distinct from what you may find in the kitchen. However, many of the sink's components are common across all versions.

Here are some of the most typical components of a sink that you'll encounter in almost every bathroom:


The faucet is the component of a sink where water flows out. The water spout, controls, gaskets, flanges, aerators, washers, and various screws could all be found on the faucet of your kitchen or bathroom sink.


Controls are what allow you to activate the tap water. Single lever types that rotate to regulate water temperature and separate left and right hot/cold controls are prevalent. You may pick the style that works best in your house while still looking nice since there are so many different designs available.


The basin is the element of the sink that keeps water from the faucet. It has a drain in its base that allows water to flow out.


Sinks have drains that enable water from the faucet to flow out of the sink basin. The drain is linked to your P-trap and plumbing connection, which are concealed within the walls.


The drain tailpiece is a component of piping that connects to the drain fitting at the bottom of the sink. It takes water away from the sink.

Water supply lines

These attach to the sink’s faucet controls. They provide each sink with its own supply line for hot and cold water.


A P-trap is a two-part pipe that allows waste and water to pass through beneath your sink. The bend in the pipe prevents sewer gas from entering. Today, most models are two pieces welded together.


A cleanout is a pipe fitting that allows you to clear clogs and remove waste near the P-trap.

Shut-off valve

A shut-off valve, which is attached to a flexible braided metal line and resembles an oval-shaped handle, is placed near a sink to help you regulate the water flow. Individual limits may also be referred to as stops.


Bathroom sinks typically have a drain that can be closed to hold water in the basin. Stoppers are bathroom drains with a fitting that goes inside the drain and a lift rod to raise and lower the stopper valve.

Strainer nut, rubber gasket and friction gasket

The strainer flange and P-trap must be fully connected to create a watertight seal. Plumber's putty is commonly used to keep these components in position.

Diagnose The Source of the Leak

plumber fixing a bathroom sink leak

The first step in repairing your bathroom sink leak is locating the leak. The main causes of bathroom sink leaks are lose pipe connections, a bad drainpipe, or a leaky drain flange. Once you've figured out where the leak is coming from, you'll be able to take the appropriate action. The faulty component may be repaired or replaced.

Leaks in a bathroom sink are frequently caused by clogged water supply lines, faulty p-traps, or poor sink drain pipe connections. Other reasons for bathroom sink leaks include blocked water supply pipes, incorrect p-traps, and poor sink drain connections; so double-check these areas.

Around the sink drain or water supply lines, lay paper towels. Check back in a few hours to see if the towels have water stains. To discover the genuine source of the leak, you must do a thorough inspection.

Leaks from a leaky faucet are generally the result of worn or damaged parts. Although it's unlikely, a worn-out faucet might also cause leakage. If your faucet is old, the tailpieces may be corroded, rendering tight connections impossible. However, not all of the leaking in your bathroom sink comes from the faucet. Fittings or sink drain holes may also be leaking.

If this is the case, simply tighten the sink drain connections. If the drain strainer and tailpiece units are worn out, consider replacing the sink drain fitting. You can usually fix the leak simply by tightening the loose connections.

Now if you're able to identify the source of the leak, it's time to attempt repairing the leak. Read on below to find the corresponding source of your bathroom sink leaking for action steps.

Leak Coming From The Shut-Off Valves

The hot- and cold-water supply shut-off valves must be replaced. You'll need to turn off the main water supply. Shut-off valves are either screwed on with a compression fitting or soldered on, which necessitates the services of a plumber.

Leak Coming From The Water Hose

Remember to inspect for leaky pipes or your supply lines. To tighten the connection, use a pair of pliers. If that doesn't work, remove the hose and inspect the gasket to see whether it's worn and needs to be replaced.

Leak Coming From The Sink Drain

Leaks from the drain-assembly are the most difficult to repair and almost certainly need the assistance of a specialist. If you're ambitious and want to give repairing a bad drain pipe a try, the P-trap is first removed before the drain is. Wrap the drain threads with plumber's tape and replace the drain and P-trap.

Leaky Sink Drain Flange

You may want to call a plumber for a leaky sink flange too. Remove the sink drain and check it for any leaks. Clean it if necessary, and if the flange is damaged, replace it. You'll need to reconnect everything as it was before when you're done.

Leak Coming From The P-Trap

The P-trap is the curved-shaped pipe beneath the drain. The P-traps are held together with a slip nut connecting it to the sink pipe. Tighten any loose slip nut using hand tools and, if that fails, an adjustable wrench, pipe wrench, or pliers to tight any slip nuts.

ARS/Rescue Rooters Can Stop Leaking Bathroom Sinks

It's all about how comfortable you feel when dealing with resolving leaks. If you think you can tackle it yourself with a trip to the hardware store, more power to you! But not all leaks are the same, and not everyone is equipped to handle a DIY repair.

That's where the plumbing professionals at ARS/Rescue Rooter come in! Our certified plumbers across the country are standing by to restore your home's plumbing system into proper working fashion.

Call our plumbers at 866-399-2885 or find your nearest ARS/Rescue Rooter location to schedule plumbing repair service today!

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