How to Fix a Leaking Single-Handle Faucet
Stop water waste and leaks on a single-handle faucet by replacing worn internal cartridges, O-rings, and rubber valve seats step-by-step.
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🧰 Required Tools & Equipment
- ✓ Hex key (Allen wrench) set
- ✓ Adjustable wrench
- ✓ Flathead screwdriver
- ✓ Needle-nose pliers
- ✓ Dental pick or small utility pick
📦 Materials & Supplies
- ✓ Replacement cartridge or O-ring/spring kit
- ✓ Plumber's silicone grease
- ✓ Clean rags or shop towels
- ✓ White vinegar
⚠️ Safety Checkpoints & Warnings
- • Confirm water supply valves beneath the sink are turned fully clockwise to avoid pressurized spray.
- • Place a rag over the open sink drain before removing screws to prevent tiny parts from falling down the pipe.
- • Ensure no mineral cleaner or chemical touches decorative faucet finishes for extended periods.
📋 Step-by-Step Guide (7 Steps)
Shut Off Water Supply and Cover Drain
Locate the hot and cold shut-off valves directly beneath the sink. Rotate both oval handles clockwise until completely tight. Open the faucet handle to release remaining water pressure, then drape a clean shop towel directly across the sink drain opening.
- • Both under-sink valve handles turned perpendicular or fully clockwise.
- • Faucet handle open with zero water trickling out.
- • Sink drain covered completely with a towel.
- • Forgetting to relieve residual line pressure before disassembly.
- • Leaving the drain open, allowing set screws to drop inside.
Remove Handle and Decorative Cap
Pry off the small plastic index button (red/blue or logo plug) on the handle using a flathead screwdriver or pick. Insert the matching hex key into the exposed hole, loosen the set screw counterclockwise 3 to 4 turns, and pull the handle straight up off the faucet body.
- • Index plug removed cleanly with no scratching on the finish.
- • Handle separated cleanly from the valve stem, exposing the dome collar.
- • Backing the set screw out all the way until it falls out and gets lost.
- • Yanking the handle sideways instead of pulling straight upward along the stem axis.
Unscrew Retaining Collar or Nut
Unthread the smooth decorative dome cap by hand turning counterclockwise. Fit an adjustable wrench onto the flat edges of the brass retaining nut underneath, hold the spout body steady, and turn counterclockwise to remove the nut.
- • Decorative dome unthreaded and removed.
- • Brass retaining nut completely unscrewed, exposing the top of the internal cartridge.
- • Using serrated pliers on the decorative chrome dome without padding, scratching the finish.
- • Letting the entire faucet base twist on the countertop while breaking the retaining nut free.
Extract the Worn Cartridge or Valve Core
Grasp the exposed brass or plastic stem of the cartridge with needle-nose pliers or your fingers. Pull straight up firmly along the vertical axis of the valve body until the cartridge slides out completely. If equipped with a retaining clip (common in Moen faucets), pull that clip out horizontally first.
- • Retaining clip (if present) removed and placed on rag.
- • Old cartridge fully removed from the cylindrical brass valve cavity.
- • Trying to pull the cartridge while the U-shaped retaining clip is still locked in place.
- • Twisting the cartridge violently, which can snap plastic alignment tabs inside the housing.
Clean Housing and Replace Seats and Springs
Look inside the brass cavity for rubber seats and internal springs (common in ball-type valves). Use a dental pick to lift them out, noting spring orientation. Wipe the inside of the cavity with a vinegar-dampened towel to remove all white mineral crust, then insert new springs (wide end down) and rubber caps.
- • Internal brass housing free of white lime scale and black rubber residue.
- • New springs and rubber seats sitting flush and upright in their internal ports.
- • Installing conical springs upside down (narrow end must face into the rubber seat).
- • Leaving old degraded rubber flakes stuck to the bottom sealing face.
Insert New Cartridge and Align Tabs
Apply a thin film of plumber's silicone grease around the O-rings of the new replacement cartridge. Align the raised plastic keys or tabs on the cartridge body with the matching slots inside the brass valve housing. Push the cartridge straight down until it seats completely flat.
- • Cartridge ears or indexing tabs locked fully into the matching brass housing notches.
- • Top rim of the cartridge sitting completely flush with the top lip of the housing.
- • Installing the cartridge 180 degrees backward, reversing hot and cold water controls.
- • Forcing the cartridge down without aligning the key tabs, crushing the plastic alignment ears.
Reassemble, Restore Water, and Test
Reinstall the retaining clip or thread the retaining nut back on snugly with an adjustable wrench. Screw on the decorative dome, reinstall the handle, and tighten the set screw. Turn under-sink shutoff valves fully counterclockwise, remove the drain rag, and cycle the handle through hot and cold to purge air and confirm no leaks.
- • Retaining nut, dome, and handle fully secured with index plug replaced.
- • Water running in a smooth, aerated stream with zero dripping from the spout or handle base when shut off.
- • Overtightening the retaining nut, which makes the handle stiff and difficult to move.
- • Turning water on full blast instantly, causing a water hammer surge that blows out aerators.
Credit: inspired by an original tutorial by Lowe's Home Improvement — watch the original on YouTube.
Don’t have everything?
- No Dental pick or small utility pick? Bent paperclip or wooden toothpick
- No Plumber's silicone grease? Water-based pipe lubricant (Do NOT use WD-40 or Vaseline)
- No Hex key (Allen wrench) set? Appropriately sized Torx key if it matches the set screw profile