What Is a Faucet Supply Line?
The flexible hose that carries water from the shutoff valve under the sink up to the faucet. It is cheap and worth replacing with any new faucet.
A short flexible hose, usually braided stainless steel over a rubber or plastic liner, with a threaded nut on each end. One end connects to the shutoff valve under the sink and the other to the faucet tailpiece. Faucet supply lines are commonly 3/8 inch at the valve end and come in lengths from 12 to 36 inches. They wear from the inside, so a line older than about ten years is a leak waiting to happen.
The connection seals by compression, not by tape: a soft ring crushes against the fitting as the nut is tightened. Hand-tight plus a quarter turn is the whole rule, and extra force crushes the ring. A plastic nut on an old line cracks with age, which is the usual reason a supply line floods a cabinet. When you replace a faucet, replace both lines, at $8 to $15 each.
Fixes that use this
Laundry & Cleaning
Dryer Takes Too Long? It's Almost Always Airflow
A dryer that needs two cycles is starved for air, not short on heat. Test the lint screen with water, then clear the duct run from both ends.
Time45–90 min Cost$0–$40 moderate
Kitchen
How to Fix a Leak Under the Kitchen Sink in One Evening
A leak under the kitchen sink is a supply line, the faucet, a drain joint, or the dishwasher hose. A 10-minute test finds which. Most fixes are under $15.
Time30–90 min Cost$0–$25 easy
Kitchen
How to Fix a Leaky Faucet (Find the Right Part First)
A dripping faucet is a worn cartridge, washer, or seal. How to identify your faucet type, buy the right $5–$20 part, and swap it in under an hour.
Time30–60 min Cost$5–$20 moderate
Kitchen
Refrigerator Leaking Water Inside? Check the Defrost Drain
Water pooling under the crisper drawers points to a frozen defrost drain. Clear it with warm water and a baster, no parts, in about 30 minutes.
Time30–45 min Cost$0–$15 easy
Bathroom
How to Replace a Toilet Fill Valve in 30 Minutes
A bad toilet fill valve hisses, refills slowly, or will not hold the water level. Shut off the supply, swap the valve, set the height, and test it.
Time30 min Cost$12–$20 moderate
Bathroom
How to Fix Banging Water Pipes (Water Hammer) in One Evening
A bang when a faucet shuts off is water hammer. Check pressure, strap loose pipes, and fit a $15 arrestor on the noisy fixture. Most fixes are under $40.
Time30–90 min Cost$5–$60 moderate
Bathroom
Toilet Leaking at the Base? Replace the Wax Ring
Water around a toilet base is usually a failed wax ring or loose bolts. Tighten first, then replace the $6 ring if the floor stays wet. A first-timer job.
Time45–90 min Cost$8–$30 moderate
Kitchen
How to Replace a Kitchen Faucet in 90 Minutes
Swapping a kitchen faucet takes a basin wrench, a new faucet, and an evening. Shut off the water, remove the old one, mount the new one, flush the aerator.
Time60–120 min Cost$60–$250 moderate
Outdoors & Seasonal
How to Thaw Frozen Pipes Safely Before They Burst
No water from a faucet on a freezing day means a frozen pipe. Open the tap, warm the pipe with a hair dryer from the faucet end, and never use a flame.
Time30–90 min Cost$0–$30 easy
Related terms
Flapper Fill valve Overflow tube Dye test P-trap Faucet cartridge Shutoff valve Biofilm