Adjustable wrench
Use it for: Loosens and tightens the supply line nuts at the shutoff valve and faucet connection.
Shop adjustable wrenchesKitchen sink plumbing
How to Replace a Kitchen Sink Supply Line
To replace a kitchen sink supply line, confirm the leak is coming from the line or its fittings, shut off the water at the sink valves, remove the old line, install a matching new line without kinks, then turn the water back on slowly and check for leaks.
This is a straightforward repair if the shutoff valves still work and the leak is limited to the supply line or its connections. The key is buying the right length and end fittings, then tightening the new line enough to seal without forcing the threads.
Before you start: Match the line length, end sizes, and connection type before ordering.
Safety first
- Work with the shutoff valves fully off before disconnecting the old line.
- Keep a bucket and towels under the work area because even a drained line will spill some water.
- Use steady wrench pressure and avoid twisting the shutoff valve or faucet connection.
- Do not overtighten supply line nuts; too much force can damage fittings and create a new leak.
Tools you may need
Small bucket or bowl
Use it for: Catches the water left in the line when you disconnect it.
Find a small drain bucket
Towel or rags
Use it for: Protects the cabinet floor and helps you spot fresh drips during testing.
Shop absorbent shop towels
Flashlight or work light
Use it for: Lets you see the back of the faucet and the shutoff connections under the sink.
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Step-by-step fix
Step 1: Confirm the supply line is the problem
- Empty the area under the sink so you can see both shutoff valves, the supply lines, and the faucet connections clearly.
- Dry the supply line, shutoff valve, and faucet shank area with a towel.
- Run the faucet for a minute, then watch for where fresh water appears.
- Look for drips from the braided or plastic line itself, from the nut at the shutoff valve, or from the upper connection at the faucet.
- Make sure the leak is not coming from the drain, sprayer hose, garbage disposal, or water lines feeding another fixture.
If it works: You have traced the leak to the kitchen sink supply line or one of its end connections.
If it doesn’t: If the water is coming from the faucet body, shutoff valve, drain parts, or another hose, fix that part instead before replacing the supply line.
Stop if:
- The shutoff valve is leaking from the valve body or stem instead of the supply line connection.
- The cabinet, wall, or floor shows swelling, rot, mold, or hidden water damage that needs a larger repair.
Step 2: Shut off the water and match the replacement line
- Turn off the hot and cold shutoff valves under the sink by turning them clockwise.
- Open the faucet to relieve pressure and confirm the water flow stops.
- Place a bucket and towel under the line you are replacing.
- Check the old line length and both end connections before removing it.
- Use the new line only if its length, end sizes, and connection style match the old one.
If it works: The water is off, pressure is relieved, and you have a matching replacement line ready to install.
If it doesn’t: If a shutoff valve will not fully close, you may need to shut off the home's water supply before continuing.
Stop if:
- A shutoff valve will not close, spins freely, or starts leaking heavily when you touch it.
- The replacement line does not match the old line's connection sizes or fitting style.
Step 3: Remove the old supply line
- Use the adjustable wrench to loosen the lower nut at the shutoff valve while supporting the valve gently with your free hand if needed.
- Let the remaining water drain into the bucket.
- Loosen the upper connection at the faucet and remove the old line completely.
- Wipe both connection points clean so the new line can seat properly.
- Inspect the old line for splits, corrosion, or damaged washers so you know the leak source was real.
If it works: The old supply line is out and both connection points are clean and accessible.
If it doesn’t: If a nut is stuck, apply steady pressure and reposition the wrench for a better grip rather than forcing it sideways.
Stop if:
- The faucet connection is cracked, badly corroded, or spins in a way that suggests the faucet mounting is failing.
- The shutoff valve or pipe starts twisting in the wall or floor when you try to loosen the line.
Step 4: Install the new supply line
- Start the upper connection by hand first so you do not cross-thread it.
- Start the lower connection by hand at the shutoff valve.
- Route the line in a smooth curve with no sharp bend, twist, or kink.
- Tighten each connection snugly with the wrench after hand-threading is complete.
- Do not add thread tape to compression-style supply line connections unless the fitting instructions specifically call for it.
If it works: The new line is installed with both ends threaded cleanly and the line routed without strain.
If it doesn’t: If the nut will not thread smoothly by hand, back it off and realign it before tightening again.
Stop if:
- The fitting cross-threads, will not seat squarely, or needs excessive force to start.
- The new line is too short, too long to route safely, or rubs sharply against other plumbing or cabinet edges.
Step 5: Turn the water back on slowly and check for leaks
- Close the faucet if you left it open.
- Turn the shutoff valve on slowly for the line you replaced, then turn on the other valve if you shut off both.
- Watch the upper and lower connections closely with a flashlight as pressure returns.
- If you see a slow drip at a connection, tighten that nut slightly and check again.
- Wipe the fittings dry and leave a dry paper towel or rag under them for a few minutes to catch small leaks.
If it works: The line holds pressure with no visible drips at either connection.
If it doesn’t: If a connection still drips after a slight retightening, shut the water back off, disconnect it, and check for a mismatched fitting or crooked connection.
Stop if:
- Water sprays, the leak gets worse quickly, or the shutoff valve itself begins leaking under pressure.
- A fitting will not seal after careful reinstallation with the correct matching line.
Step 6: Verify the repair in normal use
- Run both hot and cold water at the faucet for a few minutes.
- Move the faucet handle through normal use while watching the new line under the sink.
- Check again after 10 to 15 minutes, then once more later in the day for any fresh moisture.
- Make sure the line is not rubbing, pulling tight, or touching anything hot or sharp inside the cabinet.
- Put your items back under the sink only after the area stays dry.
If it works: The sink works normally and the cabinet stays dry during and after real use.
If it doesn’t: If moisture returns later, dry everything again and trace the exact source before tightening anything else.
Stop if:
- You find a second leak from the shutoff valve, faucet body, or another plumbing connection that was hidden by the original drip.
Replacement Parts
Find a kitchen sink supply line on Amazon
Match the line length, end sizes, and connection type before ordering.
As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Verify the repair
- No water drips from the upper faucet connection or lower shutoff connection with the faucet off.
- Hot and cold water both run normally after the repair.
- The new supply line has a smooth bend and is not kinked or under tension.
- The cabinet floor and paper towel under the fittings stay dry after several uses.
FAQ
How do I know if the supply line is bad or just loose?
Dry the line and fittings, then run the faucet and watch closely. If water appears at a nut, the connection may be loose or crooked. If water beads up from the braided hose or plastic tubing itself, the line has failed and should be replaced.
Do I need thread tape on a kitchen sink supply line?
Usually no. Most sink supply lines seal with compression fittings or built-in washers, not thread tape. Adding tape where it does not belong can actually make sealing worse.
Can I replace just one supply line?
Yes. If only the hot or cold line is leaking, you can replace that one line. Many homeowners replace both if they are the same age and equally worn, but it is not required.
What if the shutoff valve will not turn off all the way?
If the valve will not stop the water completely, shut off the home's main water supply before removing the line. If the valve leaks from the stem or body, the valve itself likely needs repair or replacement.
How tight should the new supply line be?
Start both ends by hand, then tighten them snugly with a wrench. The goal is a watertight seal, not maximum force. If it drips, tighten a little more and recheck rather than cranking hard on the fitting.