How To Fix A Broken Pipe Under The Kitchen Sink | Quick No-Mess DIY

Water on the cabinet floor and a hissing or dripping sound can send anyone into panic mode. This guide walks you through a calm, safe repair of under-sink plumbing. You’ll pin down what failed, stop the leak fast, make a clean repair, and keep the area dry after you’re done. No jargon. No guesswork. Just clear steps and a tool list that fits real homes.

Under-Sink Plumbing 101

The space below a kitchen basin usually holds two systems: the drain set (basket strainer, tailpiece, trap, trap arm) and the water supply set (shutoff valves, supply lines, and the faucet inlets). Breaks show up as cracks in plastic parts, split hoses, rusted thin spots, loose slip-joint nuts, or a corroded metal trap. Your first task is to find which system is leaking so you can choose the right fix.

Common Failures And Fast Fixes

Match the symptom to the cause. Then pick the repair path.

Symptom	Likely Cause	Quick Fix
Drip only when running water	Drain trap or trap arm leak	Tighten or replace slip-joint parts; renew washers
Constant drip, even with taps off	Pressurized supply line split or valve failure	Shut valve; replace hose or valve; test
Slow cabinet puddle under metal trap	Pinholes from corrosion	Replace trap with new metal or PVC kit
Water at back wall	Loose trap arm into wall bend	Reseat with new slip-joint washer
Sudden spray	Burst braided hose	Close angle stop; swap hose; check crimp ends
Leak only when disposer runs	Disposer discharge or gasket issue	Reclamp discharge tube; replace mounting gasket
Musty smell days later	Hidden damp wood or mold	Dry thoroughly; clean per health guidelines

Safety And Prep

Clear the cabinet. Unplug devices under the sink. Place a pan or bucket under the work area and lay a towel nearby. If spray is active, shut the nearest stop valves; if they stick or won’t close, turn off the house valve and open a tap to bleed pressure. Wear gloves and eye protection when cutting pipe or using cement.

Fixing A Broken Kitchen Sink Pipe — Step-By-Step

Step 1: Confirm The Leak Source

Run water while watching each joint with a flashlight. For supply leaks, wrap a dry tissue around each connection; wet spots tell you which joint failed. For drain leaks, fill the basin, pull the stopper, and watch the trap, trap arm, and tailpiece. Mark the wet joint with painter’s tape so you don’t lose track.

Step 2: Stop The Water

Turn the small chrome or plastic knobs (angle stops) clockwise to shut off hot and cold. If valves spin or freeze, close the main valve. In many homes that valve sits in a basement, crawlspace, garage, or an exterior box. Open a nearby tap to release pressure before you disconnect anything.

Step 3: Choose The Repair Path

Drain Parts (No Pressure)

Most kitchen drains use a P-trap linked with slip-joint nuts and conical plastic washers. Cracks, cross-threaded nuts, or a warped washer cause drips. The fix is simple: replace the damaged section piece for piece. A basic trap kit includes a new trap, trap arm, and assorted washers. Dry-fit first so lengths and angles match the old path. If a metal trap failed from rust, swap to a chrome-plated brass kit or a PVC kit that matches the rest of the run.

Supply Parts (Under Pressure)

Flexible braided hoses feed the faucet. A bulge, frayed braid, or wet crimp means the hose is done. Replace both hot and cold hoses to keep wear even. If a shutoff valve weeps at the stem or won’t close, plan a valve swap. Push-fit valves work on copper, CPVC, and PEX and make a fast, clean change with a pipe cutter and a deburring tool.

Step 4: Remove The Failed Section

For drains: back off slip-joint nuts by hand or with light wrench pressure. Catch the water in your pan. Keep the old parts in order so you can match them at the store. For supplies: place the bucket under the hose ends, loosen at the faucet first, then at the valve. If a push-fit valve is coming off, use the release clip; twist and pull straight.

Step 5: Install The Replacement

Rebuilding The Trap

Slide the nut and washer onto the tube in the right order and direction. Seat the washer cone toward the joint. Hand-tighten, then give a gentle final snug with pliers. Over-tightening can distort the washer and cause a leak. Keep the trap arm pitched slightly toward the wall so water flows and the trap stays full.

Swapping Supply Hoses Or Valves

Wrap male threads with PTFE tape in the same direction the nut turns so the tape does not unwind as you tighten. Two to four wraps do the job. Start the nut by hand to avoid cross-threading, then finish with a wrench until snug. Do not crank hard on small brass fittings; firm plus a touch more is the sweet spot.

Step 6: Test And Inspect

Open the valves slowly. Run cold, then hot. Look and feel for damp spots at every joint. Wipe with a dry tissue to catch tiny leaks you can’t see. If a slip-joint weeps, nudge the nut a hair tighter or reseat the washer. If a threaded joint seeps, back it off, rewrap, and try again.

What If The Break Is In Rigid Pipe?

A crack in PVC, ABS, or copper may sit before or after the trap or close to a valve. You can cut out the damaged section and splice in a new piece. Here’s a clean method that keeps parts aligned and serviceable.

Rigid Drain (PVC Or ABS)

Mark cut lines at least an inch past the damage on each side. Use a fine-tooth saw or a plastic pipe cutter for square cuts. Dry-fit a repair coupling and a short pipe section. For PVC, prime both sides, then apply solvent cement and push the parts fully home with a quarter turn. For ABS, use the one-step cement listed for ABS. Hold still for 30 seconds so the bond sets. Rebuild the trap as needed.

Rigid Supply (Copper, CPVC, Or PEX)

Shut the main valve, drain pressure, and cut out the split. Deburr inside and outside the pipe so push-fit couplings seal. Slide on a push-fit straight coupling with a fresh section of pipe cut to length. For copper, many people choose push-fit to avoid soldering inside a cabinet. If you prefer crimp or expansion on PEX, follow the tool maker’s steps and the color-coded rings.

Dry-Out And Clean-Up

Leaks under a sink can soak wood and particleboard. Pull the trash bin and cleaners out so air can move. Run a fan into the cabinet, or prop the doors open and aim a room fan across the opening. Discoloration or a musty odor points to lingering moisture. Clean and dry the area fully to keep the space healthy. For safe cleanup steps, see the CDC mold cleanup guide.

Code-Savvy Notes That Save Time

Most kitchen traps seal with slip-joint nuts and conical washers. See the UPC 1003.2 slip-joint fittings note for limits on joints and adapters. That small detail prevents chronic drips and loose joints. If you are replacing a corroded metal trap with plastic, bring the old adapter to match sizes and threads.

Homes built before 1986 may have solder that contains lead on copper lines or fittings. The EPA lead in drinking water page explains risks and testing. If you plan supply work in an older house, test water and plan upgrades with lead-free parts. Even a small repair is a good time to check risk and improve safety in that cabinet zone.

Materials And Tools

Here’s a lean kit that covers the most common repairs. You can gather these in one trip and keep extras in a labeled bin under the sink for next time.

Item	Purpose	Notes
P-trap kit (PVC or metal)	Replace cracked or rusty trap	Match size (usually 1-1/2 in.)
Slip-joint washers & nuts	Stop weeps at drain joints	Keep a small assorted pack
Braided faucet supply hoses	Swap leaking lines	Measure length; check faucet thread type
PTFE tape	Seal male threaded joints	Wrap in nut-turn direction
Adjustable wrench & tongue-and-groove pliers	Tighten nuts without damage	Use light, even pressure
Buckets, towels, flashlight	Catch water and light the work	Keep within reach
PVC/ABS cement and primer	Bond plastic pipe	Match cement to pipe type
Pipe cutter & deburring tool	Square cuts on copper/PEX/CPVC	Clean edges for push-fit
Push-fit couplings/valves	Quick splice on supply lines	Great for tight cabinets
Fan or dehumidifier	Dry the cabinet	Run until wood reads dry

Leak-Free Assembly Tips

• Dry-fit every part before you open glue or wrap threads.
• Keep slip-joint washers facing the right way; cone points into the fitting.
• Hand-tighten first; tool-snug last. If a joint leaks, add just a touch more.
• Do not mix different plastic types without the right adapter.
• Rebuild wobbly baskets and disposer gaskets while you’re in there.

When To Call A Pro

Bring in a licensed plumber if shutoff valves won’t close, if you see scorched marks from past soldering, if black mold spreads across the cabinet, or if the break sits inside the wall. A pro can swap old angle stops, reroute a trap arm, or replace a section of copper line fast, with less cutting and cleanup.

After The Fix: Prevent Repeat Leaks

Open and close the angle stops twice a year to keep them from seizing. Replace supply hoses every 5–7 years or at the first sign of bulging or rust at the crimps. Keep heavy bins off the trap and hoses so they don’t rub or flex. Add a small drip tray or leak sensor under the cabinet base for early alerts.

Printable Mini-Checklist

Stop, swap, test, dry. That’s the whole rhythm. Here’s the quick version you can tape inside the door:

• Shut local valves; if stuck, close the main.
• Bucket under the work; unplug nearby outlets.
• Identify drain vs. supply leak.
• Remove failed part; match like-for-like replacement.
• Rebuild with fresh washers or new hoses.
• Wrap threads with PTFE tape; snug, don’t crank.
• Turn water on slowly; check each joint.
• Dry the cabinet; run a fan until wood is dry.