Turn off the water, dry the joint, and find out how it is made. A threaded joint is remade with fresh thread sealant, a compression joint is tightened or has its ring replaced, and a soldered copper or glued plastic joint is cut out and replaced. Sealants and clamps only buy time, and some joints are not worth saving. This page sits in our guide to plumbers for leaks, which covers when a leak is bigger than a joint.
How do you tell what kind of joint is leaking?
Look at how the two pipes meet. Threaded joints show screw threads and a thick fitting. Soldered copper joints have a silver collar with a thin bead of metal around the edge. Glued plastic joints show a smooth fitting with a ring of dried cement, and compression joints use a nut and a brass ring.
Dry the pipe fully and wait a minute. Water that reappears at the edge of the fitting is a joint leak. Water that appears on the pipe a few inches away may have run along it from somewhere else, so follow the drip upward before you change anything.
Material matters too. Copper, galvanized steel, PEX, CPVC and PVC all fail at joints differently. In an older home, ask what the supply lines are made of before choosing a repair, because the wrong fitting between two unlike pipes can leak in its own right.
What should I do before I start any joint repair?
Shut off the water at the main, open the lowest faucet to drain the line, and let the pipe dry. Switch off the water heater's power or gas if the repair is on the hot side. Gather the parts first, since you will not want the water off longer than needed. Never work on gas piping yourself.
A few more checks save trouble:
- Place a bucket and towels under the joint.
- Photograph the joint, so a store clerk can match the fitting.
- Check the pipe size, which is stamped or printed on the pipe.
- Look at the pipe on both sides. If it is flaking, swollen or soft, the joint is not the real problem.
Gas leaks are different. If you smell gas, leave the building and call SoCalGas at 1-800-427-2200 from outside, or 911 if there is danger. A gas pipe joint is work for a plumber, with a permit where required.
How do you fix a leaking threaded pipe joint?
Unscrew the joint, clean both threads, wrap fresh PTFE thread tape or apply pipe thread sealant, and screw it back together hand tight plus a turn or so. Overtightening cracks fittings. If the threads are damaged, corroded or the fitting has a hairline crack, the part must be replaced.
On older galvanized steel pipe, joints may be seized with rust. Forcing them can crack the pipe or twist a connected line, and a small repair becomes a larger one. If the joint will not budge, stop and call a plumber.
New tape on a leaking thread is not a cure for a worn fitting. If the same joint weeps again within days, replace the fitting and check the pipe beyond it.
How do you fix a leaking soldered copper joint?
A soldered joint that leaks must be drained completely, heated and resoldered, or the section cut out and replaced with a new coupling. Solder will not take on a wet pipe, which is why the line has to be dry. Heating near wood framing needs a flame shield and a fire watch.
If you have never soldered, a push-to-connect coupling is a common stand-in. It slips over a clean, cut pipe and seals with an internal gripper and O-ring. Manufacturers rate these fittings for specific pipe types and pressures, so read the packaging before using one in a wall.
A leak at a copper joint can also signal a pipe problem. If you find green stains, pitting or more than one weep, pipe condition may be the issue. Our guides on repairing a copper pipe leak and fixing a pinhole in copper pipe cover that case.
How do you fix a leaking PVC or plastic pipe joint?
Cut out the leaking joint and replace it with new pipe and a coupling joined with primer and solvent cement. Gluing over a leaking glued joint does not work, because the cement welds the surfaces together only when both are clean and bare. A leak at a glued joint means the weld failed.
For drain lines, the pipe is dry once the water is stopped, so you can cut straight away. Use a slip coupling and short pipe stub so you can fit the new piece without moving the rest of the line. Let the cement cure for the time printed on the can before running water.
Can you fix a PVC joint without cutting it? A rubber repair clamp or a wrap-on epoxy kit can stop a slow drip on a drain line for a while. It is a temporary patch. If the joint carries pressure, plan to replace it.
What if you want to fix a joint without replacing it?
Leaking compression joints are the one case where the answer is often yes. Tighten the nut a quarter turn, and if the leak persists, replace the ring. Other joints can sometimes be sealed with a clamp or epoxy wrap on a short-term basis, but a joint that has failed usually needs replacement to be reliable.
Plumbers treat sealants and wraps as stopgaps because they bond to the outside of the joint and do not restore the original connection. They suit a drain line that you need to use one more night, or a supply line where you are waiting for a visit. They are not a reason to leave a joint behind drywall.
Never hide a repaired joint inside a closed wall or ceiling without a plumber's judgment. Water that escapes later can rot framing and feed mold before you see a stain.
When should you call a plumber business?
Call when the joint is in a wall, floor or slab, when the pipe is corroded, when you smell gas, when the leak is on the main, or when the repair involves a water heater, a permit or soldering you are not comfortable with. Do-it-yourself ends where the work needs a trade, or where the law requires a permit.
In Los Angeles, the Department of Building and Safety requires a plumbing permit for installation or modification of potable water piping, so a larger repair may need one. For a hired job of $over $1,000 once labor and materials are added, California requires the contractor to hold a state license, and you can check it on the CSLB site.
If your leak is recurring, the joint may not be the cause. Pressure that is too high, vibration or aging pipe can all stress joints. Send your details through the quote page and a local plumber comes to you to look at the whole line, with a written quote before work starts.
Common questions
How long does a joint repair take?
A threaded or compression joint you can reach often takes under an hour once the water is off and the parts are on hand. A soldered or glued joint takes a little longer, plus cure time for plastic cement. A joint in a wall adds time to open and close the wall. A plumber can give you a window when you book.
What should I ask before I hire someone to fix a leaking pipe joint?
Ask whether they will repair or replace the fitting, whether the price includes any wall opening and patching, whether a permit applies, and what they will do if they find more leaks. Ask for the quote in writing. If the job is $1,000 or more, check their state license number on the CSLB website.
Does someone need to be at the property?
Usually yes, at least at the start and the end. The plumber needs access to the main shutoff and the leaking area, and you will want to see the repair and test it before they leave. If someone else can be home on your behalf, tell the plumber who that is when you book the visit.
Will plumber's tape fix a leaking pipe joint?
Thread tape seals the threads of a threaded joint when it is applied during assembly. It does not stop a leak from a soldered, glued or cracked joint, and wrapping tape around the outside will not hold under pressure. If the joint is leaking at the thread, remake it with fresh tape or sealant.
Why does a pipe joint keep leaking after I fix it?
Common reasons are a cracked fitting, damaged threads, a joint that was not dry when it was soldered, glue applied to wet or dirty plastic, and a pipe under pressure that is too high. Repeated leaks can also point to vibration or corroded pipe. If your fix fails twice, bring in a plumber to check the line.