You’re washing dishes when—click—a sharp, rhythmic ticking starts under the sink, followed by a slow drip pooling near the P-trap. It’s unsettling, but not yet catastrophic. Most causes are fixable in under 30 minutes—and knowing which one you’re facing keeps you from tightening every nut blindly.
Quick Checklist
- Does the clicking happen only when hot water runs?
- Is water visibly dripping from the faucet base, supply lines, or P-trap?
- Do you hear the sound more clearly when the cabinet door is open?
- Has the sink been recently repaired or replaced?
- Is the leak worse after turning the water off?
- Can you feel vibration in the shutoff valves or supply lines when the sound occurs?
Possible Causes
Loose or worn compression nut on supply line
Confirm by gently wiggling each supply line where it connects to the faucet tailpiece and shutoff valve. If movement produces clicking or increases leakage, the compression nut is likely loose or the ferrule is deformed. Severity: DIY fix (tighten with adjustable wrench—no more than ¼ turn past snug). How to tighten a supply line nut properly
Thermal expansion in copper supply lines
Clicking only with hot water? Tap the exposed copper lines while running hot water—if they ‘ping’ audibly, expansion against framing or brackets is the culprit. Severity: Low risk; usually no repair needed unless it’s vibrating pipes into contact with wood. How to quiet expanding copper pipes
Failing cartridge or ceramic disc in faucet
Turn off water, remove handle, and inspect the cartridge for cracks or mineral buildup. If clicking coincides with handle movement—even slightly—the internal mechanism is binding. Severity: Moderate DIY (requires cartridge replacement kit); skip if faucet is >10 years old or nonstandard. Faucet cartridge replacement guide
What to Do First
Shut off both hot and cold shutoff valves under the sink—don’t rely on the main house valve unless necessary. Place a dry towel under the leak and set a shallow pan beneath the P-trap to catch drips. Then, use a flashlight to trace the wettest point: Is moisture concentrated at a joint? Dripping from the faucet body? Or pooling at the drain flange?
- Label each shutoff valve with hot/cold using masking tape—many are unmarked.
- Check the P-trap nuts: Tighten only if hand-tight plus ⅛ turn with pliers (over-tightening cracks plastic).
- Wipe all connections dry, then run hot water for 60 seconds and watch for new wet spots.
What NOT to Do
Don’t ignore intermittent clicking—even if no visible leak yet. According to the Insurance Institute for Business & Home Safety's 2023 report, 68% of under-sink leaks worsen within 72 hours of first audible symptom due to repeated stress on compromised seals.
"A single click isn’t dangerous—but three per minute during hot water use means something’s flexing or slipping under pressure. That’s your early warning system." — Carla Mendez, licensed master plumber and plumbing code advisor, Journal of Residential Plumbing Practice, 2022
- Don’t use thread seal tape on compression fittings—it interferes with the ferrule seal and often makes leaks worse.
- Don’t crank down on shutoff valve packing nuts trying to stop stem leakage; this can fracture the valve body.
- Don’t assume the faucet is fine just because it doesn’t drip at the spout—the leak may be internal and feeding the clicking sound.
Why does the clicking only happen when I turn the water off?
This points strongly to water hammer or pressure rebound in undersized supply lines. The sudden stoppage creates a shock wave that vibrates loose mounting clips or makes brass components ‘chatter.’ Install a water hammer arrester on the hot line if the issue persists after checking all connections.
Is the clicking coming from inside the wall, not under the sink?
If yes, the source is likely the shutoff valve itself—especially if it’s an older gate or globe valve with worn internal seats. These can rattle or click when flow stops abruptly. Replace with a quarter-turn ball valve (they don’t chatter) rather than re-packing.
My sink has a sprayer hose—could that be causing it?
Absolutely. A failing diverter valve inside the sprayer base often clicks and leaks simultaneously. Remove the sprayer head and check for mineral-clogged openings or a cracked rubber gasket. The U.S. EPA estimates that 14% of household water usage is from leaks—including those hidden in sprayer mechanisms.
Can a leaking garbage disposal cause clicking under the sink?
Rarely—but if the disposal’s mounting assembly is loose, vibration from operation can make adjacent pipes click against each other. Check for wobble in the unit when turned off and inspect the sink flange bolts for corrosion or missing locknuts.
Why did this start after I installed a new faucet?
New faucets often have stiffer cartridges or tighter tolerances. If the supply lines weren’t aligned perfectly during installation—or if the mounting hardware wasn’t torqued evenly—the stress can cause micro-movements that click under thermal or pressure load. Re-seat the faucet and verify supply line bends aren’t kinked or over-stressed.
Most clicking + leaking combos resolve with a $5 washer, a tightened nut, or a quick cartridge swap. But if moisture has soaked into cabinet flooring or you smell mildew, pause and assess for rot before proceeding. When in doubt, find a licensed plumber—especially if your home has PEX-aluminum composite tubing or proprietary faucet systems.