How to Fix a Leak at a Faucet Supply Line Connection
About This Project
This guide provides step-by-step instructions for fixing a common plumbing leak occurring at the connection point between a faucet supply line and the water shutoff valve. The process involves turning off the water, disconnecting the old line, installing a new one, and testing for leaks.
Best for experienced DIYers and homeowners with some experience with basic plumbing knowledge.
Tools & Materials
Unger 6 Gal. Heavy-Duty Plastic Bucket DB02
FRESHFOLDS Orange 6-Piece Cotton Quick-Dry Bath Towel Set EC100706
ITOPFOX Quick Size White High Absorbent Paper Towel Roll 100 Sheets Per Roll 8 Rolls Per Pack HDPH032OT060
Panther Vision FLATEYE F-310 High Performance 310-Lumen Unround Flashlight CREE LED Multi Position Waterproof and Shockproof FL-6960
Bucket
WYPALL L40 Towels, Dry Up Towels, 19-1/2 in. x 42 in., White, 200 Towels/Roll KCC05860
Unger 6 Gal. Heavy-Duty Plastic Bucket DB02
The Unger 6-Gallon Heavy-Duty Professional Cleaning Bucket holds more than 6 Gal. of liquid. The bucket can accommodate a scrubber up to 14 in. L. This bucket features measurement marks and 2-pour spouts
FRESHFOLDS Orange 6-Piece Cotton Quick-Dry Bath Towel Set EC100706
This cotton towel is quick-drying, absorbent and features a soft cotton popcorn texture. These towels are low-twist and two-ply, so the fibers are thicker and more durable. The weave allows for more air
ITOPFOX Quick Size White High Absorbent Paper Towel Roll 100 Sheets Per Roll 8 Rolls Per Pack HDPH032OT060
Introducing our Quick Size White High Absorbent Paper Towel Roll, the ultimate solution for your everyday cleaning needs. with its convenient quick size sheets, you can easily tear off just the right amount for any mess, saving time and reducing waste. Keep your home clean and tidy with the superior absorbency and strength of our paper towel rolls.
Panther Vision FLATEYE F-310 High Performance 310-Lumen Unround Flashlight CREE LED Multi Position Waterproof and Shockproof FL-6960
Every revolution starts with a spark. At 310-Lumens the F-310 has the power to ignite our un-round revolution without overpowering your needs or your wallet. Not your granddads flashlight these bad boys
Bucket
Ideal for carrying or storing liquids.
WYPALL L40 Towels, Dry Up Towels, 19-1/2 in. x 42 in., White, 200 Towels/Roll KCC05860
WYPALL L40 Wipers are effective wipers that absorb liquids lightning-fast. These wipes are made of bonded cellulose using DRC (double re-creped) technology for strength, softness and absorbency. As a wiping cloth, it soaks up liquids fast, but all you'll feel is softness, thanks to a plush, touchable outer layer. In fact, it's a popular choice for patient wiping in healthcare industries, for bathing and patient drying. These utility wipes are specially designed to absorb liquids, lubricants and oils (in restaurants for wiping counters, in mechanic shops, industrial and commercial factories and more), yet they're soft enough for use on face and hands. Experience the difference in superior absorbency and cleaning at your home or office today. Towel/Wipe Type: Dry Wipes; Application: Bathrooms; Material(s): Cloth-Like; Number of Plies: 1.
Steps
Prepare the Workspace
5 minsClear all items from the cabinet under the sink to create a clear and accessible workspace. Place a small bucket directly beneath the leaking connection to catch any water that will be released when the line is disconnected. Lay down several old towels or a stack of paper towels to absorb any spills and keep the area dry.
Turn Off the Water Supply
2 minsLocate the water shutoff valve for the leaking supply line. This is typically a small, oval-shaped or round handle connected to a pipe coming from the wall or floor. Turn the handle fully clockwise (to the right) until it stops. If there are two valves (one for hot, one for cold), it is best practice to shut both off.
Drain the Line and Confirm Shutdown
3 minsAfter closing the shutoff valve(s), lift the faucet handle on the sink into the 'on' position. A small amount of water remaining in the faucet and supply line will drain out, and then the flow should reduce to a trickle and stop completely. This action confirms that the shutoff valve is holding and it is safe to disconnect the line.
Disconnect the Supply Line from the Shutoff Valve
5 minsTo safely disconnect the line without damaging the plumbing, use two wrenches. Place one adjustable wrench on the body of the shutoff valve to hold it stationary. This prevents the valve and the pipe in the wall from twisting. Place the second adjustable wrench on the large nut connecting the supply line to the valve. Turn this nut counter-clockwise (to the left) to loosen and unscrew it. Be prepared for a small amount of water to spill into your bucket.
Remove Old Supply Line and Purchase Replacement
5 minsIt is most efficient to replace the entire supply line. Disconnect the other end of the line from the faucet's threaded tailpiece. This nut can be difficult to reach; a basin wrench is the ideal tool, but you may be able to use an adjustable wrench or pliers. Once removed, take the old supply line to a hardware store. Purchase a new braided stainless steel supply line of the exact same length and with the same size connection nuts.
Connect New Line to Faucet
5 minsTake the new supply line and first connect the top end to the faucet tailpiece under the sink. Thread the nut on by hand to ensure it is not cross-threaded. Tighten it as much as you can by hand. Then, use your basin wrench or adjustable wrench to give it another quarter-turn to snug it up.
Connect New Line to Shutoff Valve
5 minsNow attach the bottom end of the new supply line to the shutoff valve. Thread the nut on by hand until it's finger-tight. Then, just as before, use an adjustable wrench to tighten it an additional 1/4 to 1/2 turn. Do not over-tighten. The rubber gasket inside the nut creates the seal, not excessive force.
Restore Water and Test for Leaks
5 minsEnsure both connection nuts are snug. Very slowly, turn the shutoff valve handle counter-clockwise (to the left) to restore the water supply. Turning it on slowly prevents a sudden 'water hammer' surge of pressure. Once the valve is fully open, check both the upper and lower connections for any signs of water. Use a dry paper towel to wipe each connection; if the paper towel comes away wet, there is a leak. If you find a leak, turn the water off and try tightening the connection slightly (about 1/8 of a turn).
Final Check and Cleanup
5 minsIf there are no leaks after a few minutes, use a dry towel to wipe down the supply lines, valve, and the bottom of the cabinet. As a final check, place a dry piece of paper towel on the floor of the cabinet directly under your work. Check it again in an hour. If it's still dry, the repair is complete. You can now clean up your tools and return items to the cabinet.
Common Problems
Do not use a wrench on the plastic toilet tank connection; hand-tightening is all that is needed to create a seal and prevent cracking.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
A kinked or stressed supply line will likely cause a leak.
Solution: It is acceptable for a longer supply line to form a gentle loop.
Water can spray and cause a mess if the connection isn't perfectly sealed.
Solution: Have a rag or small bucket ready just in case there is a small leak when you first turn on the water.
If a leak is detected, immediately shut off the water and re-tighten the connection. Do not proceed until the connection is leak-free.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Turn the water on slowly to avoid a sudden high-pressure surge that could cause a loose fitting to pop off.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Failing to detect small leaks at connection points can lead to water damage.
Solution: Use a dry paper towel to wipe each connection; even a tiny amount of moisture will be easily visible on the paper.
If you see leaking, turn off the water supply, reconnect the filter, and ensure all connections are snug.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Frequently Asked Questions
How long does this repair typically take for a beginner, and what's the real difficulty level?
This is a beginner-friendly project, usually taking 30-60 minutes once you have the right parts. The most challenging aspect is often working in tight, cramped spaces under the sink. Taking your time to ensure proper alignment and avoid cross-threading is key to success.
How do I know which new supply line to buy, especially regarding size and length?
Before purchasing, measure the length of your old supply line from end to end. Note the connection sizes: faucet connections are typically 1/2 inch FIP, and shutoff valve connections are commonly 3/8 inch compression. Bringing the old line to the store or taking a picture of the connections can help ensure you get an exact match.
I replaced the supply line, but it's still leaking. What should I check next?
First, ensure both ends of the new supply line are hand-tightened, then given an additional quarter to half-turn with a wrench – avoid overtightening. Check that the rubber washer (gasket) inside the supply line nuts is properly seated and undamaged. If the leak persists, the shutoff valve itself might be old and failing, or the connection point at the faucet could be compromised.
What if I can't turn off the water supply to my faucet, or the shutoff valve itself is leaking?
If the existing shutoff valve is stuck, leaking, or won't completely stop the water flow, you will need to turn off the main water supply to your entire house before proceeding. In such cases, or if you're uncomfortable with the main shutoff, it might be best to contact a qualified plumber, as replacing a main shutoff or a frozen fixture shutoff is a more advanced task.
Do I need a specific adjustable wrench, or will any wrench do for this project?
While the project lists a specific 12-inch adjustable wrench, any good quality adjustable wrench that allows you to securely grip the nuts on the supply line and shutoff valve will work. Ensure it's sturdy and can provide enough leverage without slipping, especially in tight under-sink spaces. Make sure the jaws are clean and properly adjusted to prevent rounding the nuts.
How can I prevent these faucet supply line leaks from happening again in the future?
Periodically inspect your supply lines, especially older ones, for any signs of wear, corrosion, bulges, or crimps. When installing, always avoid overtightening the connections, as this can damage the washers or crack the nuts. Choosing braided stainless steel supply lines, like the one recommended, often provides more durability and burst resistance compared to older plastic or copper lines.
