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Around the House · Plumbing
How to fix a leak
Most leaks aren't catastrophes. They're a worn washer, a loose nut, or a compression fitting that wasn't seated right. Here's how to read the leak before you fix it — and when to put down the wrench and call someone.
The Honest Read
What this job actually involves
There are basically three kinds of household leaks: drip leaks (faucet, fixture), joint leaks (under-sink supply lines, P-traps), and pressure leaks (behind walls, in slabs). The first two are DIY-friendly. The third is not.
Before you touch anything, find the shutoff. Most fixtures have a local shutoff valve right below them. If they don't — or it doesn't turn — your main water shutoff is usually in the basement, garage, or near where the water line enters the house. Know where it is before you start.
The honest read: 80% of household leaks are a $3 part and 20 minutes of work. The other 20% need a plumber. We'll help you tell the difference.
What you need
Tools & materials
Shop the supply side here. The big-ticket stuff and the brand-restricted items, we'll point you local further down.
Tools
- Adjustable wrench (or basin wrench for tight spots)
- Channel-lock pliers
- Phillips and flathead screwdrivers
- Bucket and rags
- Flashlight or headlamp
- PTFE thread seal tape ("plumber's tape")
Materials
- Replacement washers, O-rings, or cartridges
- Supply line (braided stainless, sized to fitting)
- P-trap kit (1-1/4″ or 1-1/2″, slip-joint)
- PTFE tape
- Pipe joint compound (for threaded metal joints)
The Steps
How to find and fix the leak
01
Shut off the water
Local shutoff first. If you can't find one or it won't turn, kill the main. Open a faucet downstream to relieve pressure before you take anything apart.
02
Locate the actual leak
Dry every joint with a paper towel, then watch. A leak under the sink isn't always coming from where the water pools — it can run sideways along a pipe and drip three inches away. Mark the source with a piece of tape.
03
Diagnose the type
Faucet drip = bad cartridge, washer, or O-ring. Slow drip at a joint = nut isn't tight enough, or the washer inside has compressed. Fast drip or spray = cracked supply line or failed fitting — replace, don't tighten.
04
Take it apart
Bucket underneath. Loosen the nut with channel-locks or a basin wrench. Photograph the order parts come off in — past-you will thank present-you when you're trying to reassemble it.
05
Replace the bad part
Match washers, O-rings, and cartridges to the exact size you pulled out. Bring the old part to the store if you're not sure. Wrap male threads with PTFE tape (3–4 wraps, clockwise so it doesn't unwind when you thread it on).
06
Reassemble and test
Hand-tight, then a quarter-turn with the wrench. Don't crank — over-tightening cracks plastic nuts and crushes washers. Turn water back on slowly. Watch the joint for two full minutes. Dry the area, wait 30 minutes, check again.
Try local first · We'll wait
What to buy at the store, not online
If you're staring at the leak right now, you don't need a 5-day shipping window — you need the part today. Local hardware stores stock the consumables that make this job a 30-minute fix instead of a week-long ordeal.
- Replacement cartridges for Moen, Delta, Kohler, Pfister, Price Pfister — your local store keeps the common ones in stock
- Odd-sized washers and O-rings (the one you need is always the one you can't find online)
- PEX fittings, copper unions, and SharkBite-style connectors — sized in person beats guessing
- Pipe wrenches and basin wrenches you can return if they don't fit the job
- Real expert advice from someone who's done it a hundred times — free with the part
When to call a pro
Call a licensed plumber if: you see water in the wall, ceiling, or floor (not just under the fixture); the leak is on the supply side of a shutoff valve you can't close; you've replaced the part twice and it still leaks; you smell sewer gas; or the pipe is copper, galvanized, or anything that requires soldering or threading. A $200 service call beats a $20,000 water-damage claim.
Keep going
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