Most single-handle faucet leaks come from a worn cartridge, seals or O-rings inside the body. Turn off the water under the sink, take the handle apart, replace the worn part and reassemble.
The hard part is knowing which design you have, since cartridge, ball and disc faucets use different parts. If the faucet is old, corroded or the shutoff valves will not close, replacing it may be the cleaner fix.
Where the drip is coming from decides the repair
A faucet can leak in three places, and each one points to a different part. Water from the spout when the handle is off means a worn internal seal. Water around the base of the handle or spout means a failed O-ring or seat. Water under the sink means a supply line or connection, which is a separate fix.
Watch the leak for a minute with a dry paper towel. Mark where the first bead forms. That small bit of detective work saves a trip to the store for the wrong part.
Common internal designs, in general terms
Brands vary, but most single-handle faucets fall into one of these families.
| Design | How it works | Usual wear part |
|---|---|---|
| Cartridge | A sealed insert slides or rotates to mix and shut off flow. | The cartridge itself or its O-rings. |
| Ball | A slotted ball in the body rotates over rubber seats. | Seats, springs and the ball seal. |
| Ceramic disc | Two polished discs slide to control flow. | Disc seals or a sediment-scarred cartridge. |
| Compression-style single lever | A stem presses a washer against a seat. | Rubber washer and seat. |
Take the old part with you or snap a clear photo, because lookalike parts often differ by a small detail.
Stop the water before the repair starts
Skipping this step is how a small drip becomes a flooded cabinet.
Find the shutoff valves under the sink.
Turn each oval handle clockwise until snug. Two valves for hot and cold are typical.
Test the faucet.
Open the handle fully. If water still runs, the valves are not closing and you need the home's main shutoff.
Plug the drain.
A small screw or washer can vanish down the pipe. Lay a rag over the opening.
Know the main shutoff.
If a valve will not close or a handle snaps, shut the water at the main and call a licensed plumber.
Taking a single-handle faucet apart
Lay parts on a towel in the order they come off. Photos at each stage help on reassembly.
- Remove the handle.Pry off the small cap, loosen the set screw and lift the handle away. A hex key often fits.
- Take off the cap or collar.Unscrew the decorative cap, then any retaining nut. Use a cloth to protect the finish.
- Pull the cartridge or ball.Note the exact orientation of the notch or tab. Reinstalling it rotated is a common cause of reversed hot and cold.
- Replace seals and the worn part.Swap the O-rings and seats. Clean mineral buildup from the valve body with a soft brush.
- Reassemble and test.Tighten gently, open the shutoff valves slowly, and check around the base and spout.
Repair the faucet or replace it
Parts are cheap compared with a new faucet, but time and age matter.
Repair makes sense when
- The faucet body is clean and solid.
- Only the spout or base is dripping.
- Parts for your model are easy to find.
- The finish still looks good.
Replace when
- The body is pitted or corroded.
- Shutoff valves are stuck or leaking.
- Repairs keep failing every few months.
- You want a different style or height.
Why sediment and age make the same repair fail twice
Grit trapped in a cartridge scores the seals and shortens their life. If a repair lasts only a few months, flush the line before reassembling. Open the shutoff valve briefly with the faucet body removed and a bucket underneath to carry loose debris out.
Old brass bodies also develop mineral crust inside. If the seat is rough to the touch, a new cartridge will not seal well, and a full replacement is the honest answer. The faucet maker's repair guideline lists which cartridge fits your model, so match the part number before you buy.
If it still drips after you put it back together
A drip that survives a repair usually has one of three explanations. The new part is not the right match, a seat inside the body is scored or rough, or a nut was left too loose and lets water seep past. Take the faucet apart once more and compare the old and new parts side by side.
Check that the cartridge sits fully down in its seat and that the retaining nut is snug but not cranked. Cranking a nut can warp a seal as easily as leaving it loose. If the second try fails, stop and call, because a third attempt tends to damage the body.
Supplies worth having at hand
A short list covers almost every single-handle repair.
- Hex key set and small screwdriver.Set screws are often tiny and easy to strip.
- Adjustable wrench and a rag.The rag protects chrome from tool marks.
- Replacement cartridge or seal kit.Match the brand and model if you can read it.
- Plumber's grease.A light coat on O-rings helps them seat and last.
- Bucket and towels.Water remains in the lines even after the valves close.
Handing the job to a plumber
Call a licensed plumber when a shutoff valve will not turn, a part is seized, the faucet body is cracked, or you simply do not want to take it apart. Our faucet repair service covers cartridge swaps, supply line replacement and valve repair, with a clear price before work starts.
If the faucet is beyond saving, a new unit can go in as part of plumbing installation work, including new supply lines and shutoff valves if the old ones are tired.
What this means in Firestone, CO
Central Weld County Water District reports soft water, with an average hardness of 33 mg/L in its 2025 report. Soft water usually builds less crust inside a faucet, but grit and age still wear seals. Ask your water utility which supplier serves your address, because St. Vrain Water Authority water does not report the same figure.
If a new faucet install touches supply piping and you wonder about a permit, ask the Firestone building division, since permit rules vary. Homeowners in Dacono and Frederick should check with their own town.
Questions homeowners ask
A worn cartridge, ball seat or disc seal lets water slip past when the handle is off. Replacing the sealing part usually stops it.
Look at the handle shape and remove the cap. A visible rotating ball suggests a ball faucet. A narrow insert with a stem suggests a cartridge. Discs sit inside a wide cylinder.
Briefly, yes, but a leak at the base often means a failing O-ring. Water can seep into the cabinet, so fix it soon.
Yes. Forcing a stuck valve can break it and flood the cabinet. Shut the water at the main and call for valve replacement.
Where CWCWD supplies your home, soft water tends to leave less mineral crust than hard water. Seals still wear out, so a drip after many years is normal.