Why Is My Bathroom Faucet Leaking, and How Do I Stop It?

If you’re asking why is my bathroom faucet leaking, the honest answer is that a faucet is mostly rubber and metal pressed tightly together, and rubber doesn’t last forever. Every time you turn the handle, a soft washer or seal squeezes against a metal seat to shut off the water. After a few years of friction, mineral buildup, and pressure, that seal hardens, cracks, or wears a groove — and water finds its way through. The good news: the leak is almost always telling you exactly which cheap part has failed, and once you read the symptom correctly, the repair is simple.

Below I’ll walk you through the real reasons faucets drip, how to diagnose yours by where the water is coming from, what each fix costs, and when it’s finally time to replace the whole thing instead of nursing it along.

Why is my bathroom faucet dripping from the spout even when it’s turned off?

A steady drip from the spout when the handle is fully closed almost always means a worn washer, a bad cartridge, or a damaged valve seat — the parts responsible for shutting the water off. The water is sneaking past a seal that no longer makes a tight connection.

Which part is to blame depends on what kind of faucet you have:

• Compression faucets (two separate handles, you feel them tighten as you close them) drip because the rubber washer at the bottom of the stem has flattened or hardened. This is the single most common bathroom leak.
• Cartridge faucets (single lever, or two handles that turn smoothly only a quarter-turn) drip because the cartridge inside has worn or scaled up. You replace the whole cartridge as a unit.
• Ceramic-disc and ball faucets drip when the disc seals or the springs and rubber seats under the ball wear out.

One detail people miss: if you’ve replaced the washer twice and it still drips, the problem isn’t the washer — it’s the valve seat. That’s the metal ring the washer presses against. Once it gets pitted or scaled, it chews up every new washer in weeks. You either reface it with a seat-grinding tool or drop in a replacement seat (most compression faucets use a standard removable seat you back out with a seat wrench).

Why is water leaking from the base of the faucet handle?

If the drip shows up around the handle or the base — not the spout — and especially when the water is running, the culprit is almost always a worn O-ring or a loose packing nut. These are the seals that keep water inside the faucet body instead of weeping out around the moving parts.

This is a different repair from a spout drip, and it’s even cheaper. O-rings are small rubber rings that cost cents each and live around the spout swivel and the valve stem. Over time they dry out, flatten, or split. Tightening the packing nut a quarter-turn sometimes buys you time, but the real fix is to pull the handle, slide off the old O-rings, and roll on fresh ones with a thin smear of plumber’s silicone grease. The same skill set applies to other fixtures too — the logic behind an RO faucet O-ring replacement is identical, just on a smaller drinking-water tap.

Why is my faucet leaking underneath the sink?

Water pooling in the cabinet under the sink is NOT the same problem as a dripping spout — and it deserves attention faster, because hidden moisture rots cabinets and breeds mold. An under-sink leak almost always comes from a loose supply-line connection, a failed supply-line gasket, or corroded compression nuts where the flex hoses meet the faucet tailpiece or the shutoff valves.

Here’s how to pin it down quickly:

1. Dry everything with a paper towel, then place a fresh dry towel under the connections.
2. Run the faucet for 30 seconds and watch where the first water appears.
3. Feel the supply hoses, the shutoff valves, and the underside of the faucet body. Wet at the top of the hose means the faucet’s mounting or tailpiece seal; wet at the valve means the shutoff packing.
4. Snug the connection with a wrench — gently. Most under-sink « leaks » are just a nut that backed off a half-turn. If it still weeps, replace the braided supply line; they’re $8 and rarely worth nursing.

If the leak is at the base of the faucet where it meets the sink deck, the plumber’s putty or gasket under the faucet has failed and water is running down the mounting shank. That usually means pulling and resetting the faucet. If you’re at that point anyway, it’s worth knowing how to remove old taps from a sink without wrecking the plumbing underneath before you start cranking on corroded nuts.

How do I figure out which part is actually failing?

Match the symptom to the part — the location and timing of the leak tells you almost everything. Use this table as a fast diagnostic before you buy anything:

The pattern is clear: spout drips are sealing parts, base leaks are O-rings, deck leaks are gaskets, and cabinet puddles are connections. Diagnose by location first, then buy the part — not the other way around.

How do I fix a leaking bathroom faucet step by step?

Most bathroom faucet leaks are fixed with the same six-step routine, whether you’re swapping a washer or a full cartridge. Total time is usually 20–45 minutes.

1. Shut off the water. Turn the two shutoff valves under the sink clockwise until they stop. No shutoffs? Close the home’s main. Then open the faucet to drain the pressure.
2. Plug the drain. A rag or stopper in the drain saves you from losing the tiny screws and springs you’re about to remove.
3. Remove the handle. Pop off the decorative cap, back out the handle screw (often a hex/Allen set screw), and lift the handle off.
4. Pull the guts. Unthread the retaining nut or clip, then withdraw the cartridge or stem. Take it to the store so you buy the exact match — there are hundreds of variants.
5. Replace the worn part. Swap the washer, O-rings, springs/seats, or the whole cartridge. Smear silicone faucet grease on rubber parts before reassembly — never petroleum jelly, which destroys rubber.
6. Reassemble and test. Reverse the steps, turn the water back on slowly, and run both hot and cold for a minute while you check for drips.

A few hard-won tips: photograph each step with your phone so reassembly is foolproof; line up parts in the order you removed them; and if a part is fused with mineral scale, soak it in white vinegar rather than forcing it. The same calm, methodical approach carries over to bigger jobs — our guide on how to fix a leaking shower faucet (Moen) walks through the cartridge-puller technique that saves you when a stuck cartridge won’t budge.

Why does my faucet keep leaking even after I replaced the cartridge?

If a brand-new cartridge or washer starts leaking again within weeks, the problem is upstream of the part you replaced — usually a damaged valve seat, hard-water scale, or water pressure that’s too high. You fixed the symptom, not the cause.

Run through these in order:

• Pitted valve seat: as noted above, a rough seat shreds new seals fast. Reface or replace it.
• Hard water / mineral scale: calcium and magnesium build a crust that holds seals open and grinds away rubber. If your whole house has hard water, expect faster wear and consider a softener or at least more frequent maintenance.
• Excessive water pressure: anything above ~80 psi stresses every seal in the house. A $10 gauge on a hose bib tells you in seconds; if it’s high, a pressure-reducing valve fixes it permanently.
• Wrong or knockoff part: a cartridge that’s « close enough » but not the exact OEM model will seal poorly. Match the brand and model number.

If you’ve corrected all of that and it still leaks, the faucet body itself is likely corroded — and that’s your cue to replace rather than repair. A closely related symptom worth understanding is when a fixture won’t shut off at all; we break that scenario down in bathtub faucet turned off but hot water still running, which shares the same root causes — failed seats and worn valves — just on a tub.

Should I repair my bathroom faucet or just replace it?

Repair if the faucet is under about 10 years old, the finish is still good, and it only needs a washer, O-ring, or cartridge. Replace it if the body is corroded, you’ve fixed the same leak two or three times, replacement cartridges are discontinued, or the finish is already flaking. As a rule of thumb, if the repair parts cost more than half the price of a decent new faucet, buy new.

A quality replacement bathroom faucet runs roughly $40 to $200, and modern fixtures use ceramic-disc valves rated for hundreds of thousands of on/off cycles — far more durable than the rubber-washer compression faucets of decades past. When you’re shopping, look for a finish that resists hard-water spotting and a valve backed by a real warranty. Brushed nickel, matte black, and PVD-coated finishes hold up best against the mineral spotting that plagues bathroom faucets.

How do I keep a bathroom faucet from leaking in the future?

The best way to prevent leaks is to reduce the two things that wear seals out fastest: mineral buildup and excess pressure. A little routine maintenance roughly doubles the life of the internal parts.

• Don’t over-tighten the handles. Cranking a faucet « extra off » crushes the washer faster. Closing it firmly is enough.
• Descale yearly. Unscrew the aerator and soak it in white vinegar to clear mineral grit; this also restores weak flow.
• Keep pressure in check. Aim for 50–70 psi. Install a pressure-reducing valve if your home runs high.
• Re-grease seals during any repair. Silicone faucet grease on O-rings keeps rubber supple and sliding instead of tearing.
• Address hard water. If you constantly fight spotting and scale, a softener protects every faucet, valve, and showerhead in the house.

None of this is glamorous, but a five-minute aerator soak and the right water pressure will outlast almost any « premium » marketing claim on the box.

FAQ

Is a dripping bathroom faucet an emergency?

No, but don’t ignore it. A single faucet dripping once per second wastes around 3,000 gallons a year, and a leak around the base or under the sink can quietly rot your vanity. It’s a low-urgency, high-value fix — handle it within a week or two.

How much does it cost to fix a leaking bathroom faucet?

DIY, you’re looking at $2–$25 in parts for a washer, O-ring, or cartridge. A plumber typically charges $125–$250 for the same job, mostly labor. Since the repair is straightforward, this is one of the highest-payoff DIY tasks in the bathroom.

Can hard water make my faucet leak?

Yes. Calcium and magnesium deposits build up on valve seats and cartridges, holding seals slightly open and abrading the rubber over time. Homes with hard water see faucet seals fail noticeably faster, which is why annual descaling and water softening pay off.

Why does my faucet only leak when I turn it on?

A leak that appears only while the water runs — usually around the handle or spout base — points to a worn O-ring or a loose packing nut, not the shut-off washer. Replacing the O-rings and adding silicone grease almost always solves it.

Do I need to turn off my water to fix a faucet leak?

Yes, always. Close the two shutoff valves under the sink (or the main if there are none) and open the faucet to release pressure before you take anything apart. Skipping this step turns a tidy repair into a flooded bathroom.

How long should a bathroom faucet last before it leaks?

A decent faucet lasts 15–20 years overall, but the internal washers and O-rings are wear items that may need swapping every 5–10 years depending on water hardness and use. The faucet body usually outlives several sets of seals.

Author’s note: This guide was written by the arcorarobinet fixtures team, drawing on hands-on testing of compression, cartridge, ceramic-disc, and ball-style bathroom faucets across a range of water conditions. arcorarobinet designs and sells bathroom and kitchen faucets engineered to industry valve-durability and lead-safe standards (the kind referenced by NSF/ANSI 61 and 372), and we back our faucet bodies and finishes with a manufacturer warranty. We recommend confirming any repair against your specific faucet’s manual, since handle and cartridge designs vary by model.