Understanding the Common Causes of a Dripping Sink Faucet

A faucet that drips constantly is more than an annoyance—it wastes water, drives up utility bills, and can damage fixtures over time. While the worn-out washer is the classic culprit in older compression faucets, modern faucets have different internal mechanisms that fail in distinct ways. Identifying which part is failing is the first step toward a lasting fix.

Worn or hardened washers: In compression faucets (typically two-handle designs), rubber washers press against a valve seat to stop water flow. Over years of use, the washer dries out, cracks, or flattens, allowing water to seep past. This is the most common cause of a drip at the spout.

Corroded or mineral-encrusted valve seat: The valve seat is the metal surface that the washer presses against. Hard water deposits can pockmark or roughen this surface, preventing a watertight seal even with a new washer. Cleaning or replacing the valve seat is often necessary in areas with high mineral content.

Damaged O-rings: O-rings are small rubber rings that seal the faucet handle stem and the base of the spout. A worn O-ring can cause a leak around the handle or beneath the spout collar—often mistaken for a base leak. This is especially common in cartridge and ball-type faucets.

Loose packing nut or retaining ring: Over time, the nuts that hold internal parts together can loosen from thermal cycling and vibration. A slight gap develops, and water finds its way out. Tightening these components is a simple fix, but overtightening can crack plastic parts.

Worn cartridge or ball assembly: Many single-handle faucets use a rotating cartridge (ceramic or plastic) or a ball-and-spring assembly. These units can fail internally—scratched ceramic discs, broken ball joint, or weakened springs—leading to a constant drip even when the handle is in the off position. Replacing the entire cartridge or ball assembly is the only reliable repair.

Loose handle screws or set screws: A handle that wiggles can cause the internal stem to move slightly, preventing a full seal. Tightening handle screws (and checking the larger set screw that holds the handle to the stem) is a quick, tool-free check.

Understanding which part is failing depends on the faucet type. Modern kitchens often have a ceramic disc faucet, where a tiny scratch on one disc can cause a drip. Ball faucets (common in older kitchen sinks) rely on a spring-loaded plastic ball—worn springs or O-rings are the typical failure. Cartridge faucets (both single- and two-handle) can drip when the rubber seals inside the cartridge degrade. Take a moment to identify your faucet brand and model before ordering parts—universal replacement cartridges are available, but OEM parts often fit better.

Tools and Materials You’ll Need

Before diving into the repair, gather the right tools to avoid frustration and damage. Most sink faucet repairs require only basic household tools:

  • Adjustable wrench (or basin wrench for tight spaces)
  • Phillips and flathead screwdrivers (size #1 and #2)
  • Allen wrenches (hex keys)—common for handle set screws
  • Needle-nose pliers (for removing retaining clips or small O-rings)
  • Plumber’s grease (silicone-based) to lubricate new O-rings and washers
  • Replacement parts: washers, O-rings, valve seat, or a complete cartridge specific to your faucet model
  • Bucket or towel to catch residual water
  • Penetrating oil (like WD-40) if parts are stuck due to corrosion
  • Flashlight for illuminating under the sink
  • Safety glasses—mineral deposits and small parts can fly when prying

For compression faucets, a seat wrench may be needed to remove the valve seat. For ceramic disc faucets, you might need a special tool provided by the manufacturer to remove the cartridge retaining nut. If you don’t have the exact tool, a large channel lock with taped jaws can often substitute—but proceed carefully to avoid stripping plastic.

It’s wise to buy a faucet repair kit that matches your faucet brand. Kits often include multiple sizes of washers, O-rings, and springs. Otherwise, take the old washer or O-ring to the hardware store for a precise match—sizes vary by millimeter and using the wrong one will cause a new leak.

Step-by-Step Repair Instructions

Follow these core steps for most compression and cartridge-style faucets. If your faucet is a ball-type or ceramic disc, look for the specific variant notes below.

1. Shut Off the Water Supply and Relieve Pressure

Locate the shutoff valves under the sink—usually two small chrome or plastic knobs (hot and cold). Turn them clockwise (righty-tighty) until they stop. If there are no shutoff valves, you’ll need to turn off the main water supply for your home. After shutting off, open the faucet handle (in the usual “on” direction) to drain any water left in the line. Keep a towel or bucket under the spout to catch drips.

2. Remove the Faucet Handle

Pry off the decorative cap (often a small round or rectangular piece with an H or C) using a flathead screwdriver—wrap the tip with tape to avoid marring. Underneath, you’ll find a screw. Remove it and lift the handle straight up. If it’s stuck, apply penetrating oil and wait 5 minutes, then rock it gently. For handle screws that are stripped, use a screw extractor or a larger bit to drill them out.

3. Remove the Retaining Nut and Disassemble the Stem

With the handle off, you’ll see a large retaining nut (usually brass or plastic). Unscrew it counterclockwise with your wrench. For plastic nuts, hand-tighten only—over-tightening cracks them. Once the nut is off, pull out the faucet stem or cartridge. Note the orientation: take a photo with your phone to ensure you reinstall it correctly.

4. Replace Worn Washers and O-Rings

On a compression stem, the washer is at the bottom, held by a brass screw. Remove the screw (use a screwdriver that fits perfectly to avoid stripping), extract the old washer, and replace it with an exact duplicate. Apply a thin layer of plumber’s grease to the new washer before reinstalling. For O-rings, use a small pick or needle-nose pliers to roll the old one off the groove, then press the new one in place—do not stretch it too much, or it will fail prematurely.

5. Inspect and Clean the Valve Seat

Use a flashlight to look inside the faucet body at the valve seat. If you see rough deposits, use a seat brush (a tool with a conical abrasive pad) to polish the surface. If the seat is deeply pitted or cracked, replace it with a universal seat wrench. A damaged seat will destroy a new washer within days, so don’t skip this step.

6. Reassemble and Test

Reinstall the stem or cartridge, tighten the retaining nut (snug but not over-tightened), replace the handle, and turn the water back on slowly—open the handle to the midway position to expel air, then close it. Check for drips at the spout and around the handle base. If you still see a drip, try the specific notes below.

Extra Steps for Ball-Type Faucets (e.g., Delta)

Ball faucets have a rotating ball and two spring-loaded inlet seals. After removing the handle, use a special ball faucet tool or pliers to unscrew the cap. Lift out the ball and the neoprene seals and springs. Replace the springs and seals with a kit (O-rings around the ball’s grooves may also need replacement). Apply plumber’s grease to the new seals. Reassemble and tighten the cap only until the faucet turns smoothly—too tight will restrict movement; too loose will cause leaks.

Extra Steps for Ceramic Disc Faucets (e.g., Moen, Kohler)

These faucets usually have a single cartridge that contains two ceramic discs. Leaks are almost never caused by disc damage that can be repaired—you must replace the entire cartridge. Remove the handle (often a set screw under a cap), then unscrew the cartridge retaining nut. Use a puller tool or pry out the cartridge carefully—sometimes they’re stuck with mineral deposits. Clean the interior of the faucet body with a soft brush, apply silicone grease to the new cartridge O-rings, and press it in until seated. Tighten the nut, reinstall the handle, and test. If it still drips, the cartridge was either the wrong model or not fully seated.

Extra Steps for Cartridge Faucets with Dual Handles

Two-handle cartridge faucets work like a simpler version of the single-handle design. Follow the same handle-removal and cartridge-pull steps. Many universal cartridges are available—match the number of splines and the length of the stem. Lubricate the O-rings and ensure the cartridge ear (the tab that prevents rotation) aligns with the notch inside the faucet body.

When to Replace the Entire Faucet Instead of Repairing

Sometimes repairing a constant drip isn’t cost-effective. Consider replacing the faucet if:

  • The faucet is more than 15 years old. Internal parts become obsolete, and generic replacements may not fit. Newer faucets use less water (WaterSense certified models flow at 1.5 gallons per minute vs. older models at 2.2 GPM) and often have longer-lasting ceramic discs.
  • Multiple leaks exist. A base leak plus spout drip and handle leak indicates widespread seal failure. By the time you replace three O-rings, two washers, and a cartridge, the labor cost rivals a new faucet.
  • The faucet body is corroded or cracked. Hard water can eat through chrome-plated brass or pot metal. A hairline crack in the base or spout flange will not be repairable.
  • You have a very old two-handle faucet with no name brand. Finding correct parts may be impossible. A new WaterSense-labeled faucet can pay for itself in water savings within a year.

When buying a replacement, look for models with a lifetime warranty on the cartridge—most major brands (Moen, Delta, Kohler) offer free replacement cartridges for life. This can dramatically reduce future repair costs.

Preventative Maintenance to Avoid Future Drips

Adopting a few habits can extend the life of your faucet seals and reduce the frequency of drips:

  • Install a whole-house water softener if you have hard water (above 7 grains per gallon). Soft water dramatically slows mineral buildup on valve seats and O-rings. This is the single most effective preventative measure.
  • Operate the faucet gently—avoid overtightening handles. Compression faucets should be turned off only tight enough to stop the flow; cranking them down crushes the washer.
  • Periodically inspect for tiny drips. Place a dark cloth under the faucet overnight. Even a single drop per hour indicates a seal starting to fail—catch it early before the drip becomes constant.
  • Clean the aerator regularly. A clogged aerator can increase back pressure on the faucet cartridge, causing leaks. Unscrew the aerator (the tip of the spout) every six months and soak it in vinegar to dissolve mineral deposits.
  • Use plumber’s grease on any O-ring you install. Grease prevents the rubber from drying out and allows the O-ring to slide into place without twisting. Never use petroleum-based grease on rubber—use silicone-based plumber’s grease only.
  • Replace the entire cartridge every 10 years as a proactive measure in hard-water areas. A $15 cartridge can prevent a $250 plumber bill later.

When to Call a Professional Plumber

While most dripping faucets are DIY-friendly, certain situations warrant a licensed plumber:

  • You’ve attempted the repair and the drip persists. A plumber can use diagnostic tools (like a pressure gauge) to check for hidden issues such as a cross-connected pipe or high water pressure trimming the seal.
  • The faucet is integrated into a countertop or tile backsplash. Removing a one-piece faucet designed for a seamless installation may require cutting caulk and risking damage to adjacent surfaces. A plumber has the experience to do this without destroying the counter.
  • There is visible water damage under the sink. A persistent drip may have already softened the cabinet floor or caused mold growth. A professional can assess the extent and recommend rebuilds.
  • You’re uncomfortable working with water shutoffs. Older homes may have stuck or corroded shutoff valves that could break when turned. A plumber can replace the shutoffs safely.
  • The leak is at the base or handle with no obvious worn part. This could indicate a crack in the faucet body—a plumber can confirm and either supply a replacement or recommend a new unit.

When hiring, ask for a flat-rate estimate for faucet repair. Most plumbers charge $75–$150 for a simple washer replacement, plus parts. Compare that to the cost of a new faucet ($50–$300) and decide if DIY or pro is more economical.

The Real Cost of a Dripping Faucet

A constant drip seems minor, but the numbers are sobering. According to the EPA WaterSense program, a faucet dripping at one drop per second wastes more than 3,000 gallons per year—enough to fill 180 showers. At average U.S. water rates (around $0.004 per gallon), that’s $12 a year just in water. If you have a hot water drip, you’re also paying to heat that wasted water—energy costs can add another $20–$40 annually. Over a decade, a single unfixed drip can cost you $300–$500. Multiply that by two or three faucets in a home, and the expense becomes significant.

Beyond the financial cost, wasted water contributes to local water stress. Many municipalities face shortages; fixing a leak is one of the easiest water conservation measures you can take.

Frequently Asked Questions About Dripping Faucets

Why does my faucet drip more at night?
Water pressure in municipal systems often increases at night due to lower demand, causing a weak seal to push open. The drip itself may also sound louder in a quiet house. The fix is the same—repair the internal seal.

Can I just tighten the handle to stop a drip?
Tightening a handle on a compression faucet may temporarily stop a drip by pushing the washer harder against the seat, but this accelerates the wear on the washer. Within weeks the drip will return, often worse. Always replace the washer.

Do all faucets have a valve seat?
Only compression-style faucets have a separate replaceable valve seat. Ball, cartridge, and ceramic disc faucets have a smooth interior surface that acts as the seat—they are not replaceable but can be cleaned with a Scotch-Brite pad if scratches are minimal.

How do I find the exact replacement cartridge for my faucet?
Remove the old cartridge and look for a model number stamped on the side. Most manufacturers print a number like “1225” or “1255” (Moen), “9700” (Delta), or “GP20” (Danco universal). If no number is visible, take the cartridge to a plumbing supply store or use an online lookup tool with your faucet brand and photo. For more help, consult Family Handyman’s step-by-step guide to identify the type.

Is it safe to use plumber’s tape (Teflon tape) on faucet threads?
Only use Teflon tape on pipe threads that carry water—never on compression nuts or cartridge threads. The tape can interfere with the O-ring seal or cause the plastic nut to crack. Use silicone grease for O-rings and washers, not tape.

Conclusion

A constantly dripping sink faucet is rarely a sign of a major plumbing failure. In nearly every case, the fix lies in replacing a small rubber or plastic component—a washer, O-ring, or cartridge—that has worn out from normal use. By diagnosing the type of faucet you have and following the steps outlined above, you can stop the drip, save money, and conserve water. If you’re ever in doubt, remember that a professional plumber can usually repair a faucet in under an hour, leaving you with a quiet, efficient fixture that may last another decade. Take action today—that drip is not going to fix itself.