Turn the handle all the way off and wait thirty seconds. If water still drips from the spout, your cartridge seals have failed. That’s the clearest signal you’ll get that it’s time to replace the cartridge — and it’s a $15–60 fix you can do yourself in under half an hour.

A dripping faucet wastes about 3,000 gallons a year. Calling a plumber runs $150–300 for a cartridge swap. The cartridge itself costs $15–60, and the job requires no specialized skills — just the right part and a methodical approach.

Diagnose before you buy: Cartridge vs. seat-and-spring

Before you spend $40 on a new cartridge, verify that the cartridge seals are actually the problem. Many drips blamed on failed cartridges are actually caused by pitted cartridge seats or worn rubber springs inside the valve body — and those cost $3 to replace, not $40.

Here’s the diagnostic:

Shut off the water, remove the handle and packing nut (Steps 1–3 below), and pull the cartridge. With the cartridge out and the water still off, inspect the two small rubber components at the bottom of the cartridge cavity — the seat and spring. If the spring looks compressed or the seat surface is pitted or cracked, that’s your leak source. Replace the seat-and-spring kit (available at Home Depot or Lowe’s for $3–5) and test before replacing the cartridge.

If the cartridge slides freely when dry but water drips from the spout with the cartridge removed and water on, the issue is seat/spring, not cartridge. If the drip stops when you remove the cartridge, the cartridge seals have failed — proceed with replacement.

I’ve learned this the expensive way: replaced a Moen 1225 cartridge, still had a drip, pulled it back out, and found a visibly pitted seat I’d ignored the first time. Swapped the $4 seat-and-spring kit and the drip stopped immediately. Check the cheap part first.

What you’ll need

Tools:

  • Allen wrench set (most common sizes: 3/32” or 7/64”)
  • Adjustable wrench (for packing nuts)
  • Flashlight (to read brand markings and see set screws)
  • Cartridge puller (optional — rent from Home Depot for ~$5 if the cartridge is stuck)
  • Towel or bucket

Materials:

  • Replacement cartridge (brand and model specific — see identification section below)
  • Plumber’s grease or silicone-based cartridge grease (usually included with cartridge)
  • Seat-and-spring kit (optional — only if diagnostic above indicates need)

Prerequisites:

  • Access to shutoff valves under the sink (or willingness to shut off the main water supply)

Before you start

This is a low-risk job, but water damage from skipping the shutoff step turns it into an expensive one fast. Make sure you can locate and turn the shutoff valves under your sink before you remove the handle. If those valves are seized or missing, see the “When to call a professional” section below.

Identify the correct replacement cartridge first

This step is non-negotiable. Moen, Delta, and Kohler cartridges are not interchangeable — even within the same brand, different faucet models use different cartridges. Buying the wrong one wastes a trip and delays the fix.

Here’s the lookup sequence:

  1. Find the faucet model number. It’s usually stamped on the faucet body under the sink, on the back of the spout, or underneath the handle. Take a clear photo with your phone.

  2. Identify the brand. Common cartridge families include:

    • Moen: Models 1224, 1225, 1255 (two-handle); 1224B or Posi-Temp (single-handle)
    • Delta: RP19804, RP46074, RP50587 (each faucet series has a specific part number)
    • Kohler: GP76851, GP77759, GP1016515 (Forte, Bancroft, and other series each require their own cartridge)

  3. Cross-reference the model number. Use the manufacturer’s online lookup tool (Moen support, Delta, or Kohler support) or call their support line with the model number. They’ll confirm the exact cartridge you need.

  4. Alternatively: Bring the handle and a photo of the model number to a home improvement store plumbing counter. Staff can match it on the spot.

I’ve grabbed the wrong cartridge twice — once because I assumed “single-handle Delta” was enough information (it’s not), and once because I trusted a faucet forum post instead of checking the manufacturer’s chart. Both times cost me an extra hour and a second trip. Start here, not at the store.

Step 1: Shut off the water supply

Locate the shutoff valves under the sink — usually two small knobs or levers on the supply lines. Turn them clockwise until they stop. Then open the faucet to release pressure in the lines and drain residual water from the body. Place a towel underneath to catch the water that spills when you remove the cartridge.

If you don’t have shutoff valves under the sink, you’ll need to shut off the main water supply. That affects the whole house, so plan accordingly.

Step 2: Remove the handle

Shutoff valve handle located under kitchen sink cabinet
Photo by Ryutaro Tsukata on Pexels

Look for a small set screw at the base of the handle or hidden under a decorative cap. Use the correct size Allen wrench (typically 3/32” or 7/64”) to loosen it — you don’t need to remove it fully, just loosen enough to slide the handle off. Pull the handle straight toward you. If it’s stuck, wiggle gently; forcing it can crack the plastic collar underneath.

Step 3: Remove the packing nut or collar

Some faucets have a decorative chrome collar or a packing nut below the handle. Use an adjustable wrench to loosen it counterclockwise, then unscrew by hand. Set it aside carefully — you’ll need it during reassembly, and replacements are surprisingly hard to find.

Step 4: Extract the old cartridge

The cartridge will be visible inside the faucet body. It usually has a flat top edge, a plastic stem, or small retaining tabs. Check for a metal retaining clip or U-clip holding it in place — if present, pull it out with pliers before attempting to remove the cartridge.

Grip the cartridge stem firmly and pull straight out. If it doesn’t budge after moderate force, don’t keep pulling — you risk breaking the cartridge body inside the faucet. Instead, rent a cartridge puller from Home Depot ($5/day), insert it into the cartridge, tighten, and pull. Alternatively, soak the faucet with penetrating oil like Liquid Wrench for ten minutes, then try again.

Step 5: Inspect the cavity and prep the new cartridge

Plumber's hands removing cartridge from faucet assembly
Photo by Kindel Media on Pexels

Run a damp cloth inside the cartridge cavity to clear mineral deposits or sediment. Don’t use abrasive cleaners or steel wool — you can scratch the valve seat and create new leak points.

Check the rubber O-rings at the base of the cartridge socket. If they look cracked, shrunken, or brittle, replace them. O-ring kits cost $5–15 and extend the life of the repair.

Now check the seat and spring (the diagnostic step above). If you see pitting, cracks, or a compressed spring, replace the seat-and-spring kit now before installing the new cartridge.

Apply a thin layer of plumber’s grease (included with most cartridges) to the new cartridge’s seals. This eases insertion and protects the rubber from tearing during install. Do not use WD-40 or petroleum-based oils — they degrade rubber seals.

Step 6: Install the new cartridge — orientation matters

This is the step that causes most post-installation failures. Many DIY cartridge replacements leak immediately because the cartridge was installed rotated 180° or with stem grooves misaligned to the faucet body.

Before you insert the cartridge, identify the alignment feature:

  • Moen cartridges: Look for a flat edge on the cartridge stem and a corresponding notch inside the faucet body. The flat edge must align with the notch.
  • Delta cartridges: The cartridge has two small tabs or ears on the sides. These must seat into matching slots in the valve body.
  • Kohler cartridges: The stem has a D-shaped cross-section. Rotate the cartridge so the flat side of the D aligns with the flat side of the valve opening.

Push the cartridge straight down — do not twist or force it. You should feel or hear a slight click when it seats fully. Some cartridges have a depth line molded into the body; push until that mark is flush with the faucet body.

Test the alignment before reassembly: With the cartridge seated but the handle not yet reinstalled, turn the water back on briefly and test the cartridge stem by hand. Hot should be hot, cold should be cold, and off should stop the flow completely. If the hot/cold is reversed or the valve won’t shut off, the cartridge is rotated wrong — pull it, rotate 180°, and reinstall.

If your faucet had a retaining clip, reinstall it now.

Step 7: Reassemble and test — do not overtighten

Replace the packing nut or collar and hand-tighten it, then give it no more than a 1/4 turn with the wrench. This is critical: overtightening the packing nut immediately crushes the new cartridge seals and causes leaks within days. Most people reflexively crank it tight because it “feels” right, but cartridge seals are soft rubber — they need compression, not crushing. Hand-tight plus a quarter turn is the maximum.

Reinstall the handle, aligning the set screw hole, and tighten the screw until snug — hand-tight is sufficient. Over-tightening can strip the threads or crack the handle.

Turn the shutoff valves back on slowly. You’ll hear air bleeding out of the lines. Open the faucet and let it run for 30 seconds to clear air pockets. Close the handle fully and check for drips. If the faucet shuts off cleanly and the handle moves smoothly, the job is done.

Troubleshooting

The new cartridge leaks from the spout. Check the cartridge orientation. If the flat edge or alignment notch isn’t seated in the correct position, the seals won’t engage properly. Remove, rotate, and reinstall per Step 6 guidance.

Water leaks from under the handle. The packing nut is either too loose or too tight (yes, both cause leaks). Try loosening it slightly first — if that doesn’t work, the O-rings need replacing. Shut off the water again and replace the O-rings.

The handle is stiff or won’t turn smoothly. You may have skipped the plumber’s grease step, or the cartridge isn’t seated fully. Pull it, apply grease, and reinstall.

Drip persists even with a new cartridge. The seat-and-spring kit likely needs replacement (see diagnostic section above). Alternatively, the valve seat itself may be damaged beyond what a seat kit can fix — that’s a call-a-pro situation.

When to call a professional

This is a beginner-friendly repair, but call a plumber if:

  • You can’t locate shutoff valves under the sink and aren’t comfortable shutting off the main water supply. A plumber can locate them or install new ones if yours are seized.
  • The cartridge is stuck after an hour of soaking and gentle pulling. Forced extraction can crack the faucet body, turning a $30 repair into a $200 faucet replacement.
  • Water leaks from the faucet body or supply connections while the water is on (not just a spout drip). That indicates valve seat damage or fitting failure beyond cartridge scope.
  • You discover corrosion or cracks in the faucet body during disassembly. The whole faucet may need replacing.

For reference: a plumber call-out for cartridge replacement typically costs $150–300. The cartridge itself is $15–60. DIY saves you $120–240 in labor.

FAQ

How do I know if the cartridge is the problem or something else?

Turn the handle fully off and wait 30 seconds. If water still drips from the spout, the cartridge seals have failed. If the leak is coming from under the handle or from the base of the faucet, it’s more likely an O-ring or supply line issue. See how to fix a leaky faucet base for base leaks.

Can I use a generic cartridge instead of the brand-specific one?

No. Moen, Delta, Kohler, and other brands use proprietary cartridge designs that aren’t interchangeable. Even within a single brand, different models require different cartridges. Always match the exact part number.

How long does a faucet cartridge last?

Most cartridges last 10–20 years depending on water quality and usage. Hard water and high sediment levels shorten the lifespan. If you’ve replaced the cartridge and it fails again within a year, check your water pressure and consider a sediment filter — see how to fix low water pressure for diagnostics.

I’ve replaced faucet cartridges in rentals and in my own 1970s house more times than I’d like to admit. The pattern is always the same: the actual swap takes fifteen minutes when you get the orientation right the first time. The headache is in buying the wrong part, fighting a stuck cartridge without a puller, or — and this one cost me a second cartridge — cranking the packing nut so tight it flattened the seals before I even tested the faucet. Get the identification step right, verify alignment before you close it up, and don’t overtighten anything. This is one of the easiest plumbing wins you can do without calling anyone.

If the drip is coming from the toilet instead, the fix is just as straightforward — see How to Fix a Running Toilet in 3 Steps for that walkthrough.