Cap off water line

Cap off water line DEFAULT

How to Cap a Copper Plumbing Line

By Steve Hamilton

Soldering is a important do-it-yourself skill.

Working with copper plumbing is often troublesome for the uninitiated, but there are some tasks that can give even an avid home plumber fits. After removing a fixture, it is sometimes necessary to either temporarily or permanently cap off the supply line. Supply lines are frequently difficult to drain, making them harder to solder and turning a normally straightforward procedure into a frustrating ordeal. The solution is to create enough empty space in the pipe where you need it most, in the immediate vicinity of the end cap.

Turn off the water supply. Open a faucet on the same supply line as the one being capped to relieve pressure on the line. Drain the line as completely as possible.

Cut the copper pipe with a pipe cutter at the chosen location. Ream the inside of the pipe with the reamer attached to the pipe cutter or a separate reaming tool.

Insert 24 inches of a piece of thin vinyl or rubber tubing into the open end of the copper pipe. Start a siphon by sucking on the other end of the tubing, then hold the end over a bucket to catch the water. Drain the water level down to the point where the siphon stops, providing approximately 24 inches of empty pipe below the opening.

Clean the outside of the end of the pipe and the inside of a cap fitting with steel wool until the copper is bright and shiny.

Apply paste flux liberally to the clean outside portion of the pipe and the inside of the cap fitting using a flux brush. Slip the fitting fully onto the end of the pipe.

Place a fire extinguisher nearby. Insert a piece of cement backer board or sheet metal between the pipe and any combustible surfaces, such as wall studs, drywall or cabinetry.

Unroll a 6-inch length of lead-free solder from a roll. Light a propane torch and adjust it to obtain a strong, steady flame with a blue center cone. Apply heat to the pipe and cap fitting. Concentrate the heat on the joint to avoid heating the rest of the pipe unnecessarily.

Touch the tip of the solder to the pipe just below the cap fitting, on the side of the pipe opposite the flame. Feed solder into the joint once it starts to melt. Remove the heat and stop feeding solder when a bright silver ring forms around the entire joint at the base of the cap fitting, and when several drops of excess solder appear on the pipe.

Turn off the torch and set it carefully aside. Watch the joint for five seconds as it cools to be sure steam pressure doesn't blow any pinhole leaks in the solder seam. Wipe the joint with a damp rag.

Turn on the water and check for leaks.



  • The key to a good, leak-free soldered joint on copper pipe is cleanliness. The pipe and any fittings must be completely clean and bright. After cleaning, don't touch the surfaces to be soldered with your hands. Use plenty of flux before assembly, and have plenty of heat concentrated on the joint during soldering.
  • To quickly and temporarily cap a line so the rest of the house has water while you're doing repairs, install a compression stop valve. Push-to-connect fittings are also available that will suffice for temporary service.


  • Always wear shoes, long pants and a long-sleeved shirt as well as leather gloves and eye protection when soldering copper pipe.

Writer Bio

Steve Hamilton has been writing professionally since His credits include novels under the Dell imprint and for Harlequin Worldwide. A remodeling and repair specialist with over 20 years experience, he is also a Certified Pool Operator and holds an EPA Universal refrigerant certification.


How to Cap Water Lines

  • Turn off the water to your house at the main valve. Open all faucets.

  • Cut the line you want to cap with an adjustable pipe cutter. Remove any burrs from the end of cut copper lines with a metal file.

  • Glue a PVC end cap to PVC water lines with PVC cement. Push a Sharkbite end cap onto the end of cut copper lines where plumbing codes allow. Sharkbite fittings are self-adjusting and self-adhering.

  • Thoroughly dry the inside of cut copper lines that are to be fitted with soldered end caps using a heat gun. Steam prevents the proper installation of soldered end caps.

  • Clean the outside of the pipe and the inside of the end cap with emery cloth until both surfaces shine. Apply flux paste to the inside of the cap and to the cut pipe with your fingers. Slide the end cap over the end of the pipe.

  • Unroll about 3 inches of wire from a roll of solder wire. Light a propane torch with a match and adjust the gas flow until the torch flame is blue.

  • Heat the pipe and fitting with the torch. Touch the solder to all sides of the copper pipe when the flux begins to bubble. Ensure that the solder flows into the joint. If the solder does not flow into the joint, the pipe is still wet and steam is pushing the solder out.

  • Heat the end cap until the joint fills with solder and solder begins to accumulate outside the fitting. Remove excess solder with a wire brush.

  • Turn on the main water valve. Check the end cap for leaks.

  • Turn off all faucets. Recheck the end cap for leaks.

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    Introduction: Leave the Water on While Working on Old Plumbing

    If you are working on older plumbing, it is often difficult to turn off the water shut-off valves under the sink or behind the toilet because:

    1. The valve is corroded internally and stuck in the open position.

    2. The handle has nearly corroded away and it crumbles in your hand when you try to turn it.

    3. You are like me and you are afraid that if you close the shut-off valve, it will begin to leak when you open it again.

    4. All of the above.

    To be sure, you can turn the water off at the street, do your repair quickly (replace the faucet washer or replace the toilet flush valve) and then turn the water back on. But if the repair is going to take more time, say, because you are having new counter-tops put into all 3 bathrooms, or you find that you don’t have the right parts, then it would be nice for the rest of the people in the house if you could turn the water back on at the street while you complete the project.

    Step 1: How You Can Turn the Water Back on at the Street

    So, in that situation, how can you turn the water back on at the street (without turning off the shut-off valves) while you drive to the hardware store to look for more parts? It is simple: you can either cap off the water supply lines at the shut-off valves or you can plug the flexible water lines while they are still attached to the shut-off valves.

    Step 2: Capping Off the Shut-Off Valve Under the Sink

    To cap off the shut-off valves under a sink, you will need to know what kind of valves you have. Remove the riser or flexible water line from the shut-off valve and inspect the connector.

    A lot of older shut-off valves are 3/8” flare fittings, whereas most of the newer valves are 3/8” compression fittings. (See Photos) While it is easy to find a brass cap for a 3/8” compression fitting, it is often difficult to find a brass cap for a 3/8” flare fitting. I have found it much easier to buy a flare to compression converter fitting and then cap the compression fitting.

    Step 3: Making the Flare to Compression Conversion

    Note- If you buy a flare to compression converter, use some Teflon enriched pipe thread compound or some Teflon tape when screwing the cap onto the converter to keep it from leaking.

    Step 4: Compression Fittings Capped Off

    Above is a photo of the "compression fittings" capped off.

    One caveat: when looking for valve caps in hardware stores, don't let the salesperson try to sell you a 3/8" flare fitting cap for a gas line instead of a water line. They look similar, but are totally different. It has become obvious to me that the associates often don't realize that.

    Step 5: If You Can't Find Either a Cap or a Converter Fitting

    And if you can’t find either a brass cap for a compression type shut-off valve or the converter, it may be easier to just buy a couple of brass plugs that will screw into the faucet connector fitting (usually ½” FIP). That is to say, the fitting on the far end of the flexible hose or the pipe that goes from the shut-off valve to the sink faucet set.

    Step 6: The FIP Fitting's Gasket

    Because the ½” FIP connector has a conical shaped rubber gasket inside of it, the flat bottomed brass plug will usually seal it off fairly well. Even if it drips slightly, you can place a plastic pan under the sink while you head for the hardware store or work on your repair. No matter that you might have an ounce of water in the pan after an hour or two.

    Remember, these fittings are not intended to be permanent, but just to cap off the water to that fixture for a few hours or a day or two at most. They don't have to be perfect.

    Step 7: Here Is the Male Plug Installed in the 1/2" FIP Fitting to the Faucet Set

    Step 8: You Can Also Cap Off the Shut-Off Valve for the Toilet

    Likewise, you can cap the corroded and stuck shut-off valve (usually a 3/8” or ½” compression fitting) to the toilet flush valve while you work on this fixture. These caps are usually easy to find.

    Step 9: And the Water Heater

    Working on a water heater is usually not an issue because most water heater inlet lines have a more substantial shut-off valve similar to a hose bib but occasionally you will get one that is stuck in the open position. If that is the case, you can either cap the valve or plug the flexible line to the water heater. (See Photos) Capping that shut-off valve with a 3/4" FIP cap is usually easiest and that size fitting is plentiful in hardware stores.

    If that fitting is not available, a brass plug for a 3/4" FIP fitting can be used to plug the water heater supply line.

    Step What About Showers and Tubs?

    Unless you have some hidden shut-off valves in a wall or cabinet, I don't know of a way to cap or plug the water supply lines to these devices. Most tubs and showers do not have shut-off valves to the faucets or mixers. You will just have to turn the water off at the street and work as efficiently as you can while you replace the O-rings, packing, or mixer cartridge.

    Step In a Perfect World

    I realize that in a perfect world, I would not be facing the dilemma described in the opening paragraph, because I would have already replaced these ancient shut-off valves with modern push-fit ¼ turn ball valves- such as SharkBite style fittings.

    But, alas, I live in a house where the stub-out (the amount of pipe protruding from the wall) on my old shut-off valves is not very long or the pipe behind the valves is covered with thick paint and clumps of solder. And the SharkBite style fittings require an inch of clean pipe sticking out of the wall once the old fitting has been removed.

    Furthermore, I do not relish the idea of expanding my small plumbing project/repair into cutting out the sheet rock behind the old shut-off valve, replacing the pipe AND the valve, and then repairing the sheet rock.

    Yes, this tutorial is a quick and dirty solution, an expedient, in a less than perfect world.

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    How to Cap off Broken Copper Water Pipes

    Copper is used in many plumbing applications for its durability and resistance to corrosion. However, copper pipes are still susceptible to cracks and breaks. When it comes time to cap off a broken copper pipe, a few steps need to be taken to ensure a watertight seal. By cutting off the damaged section, refinishing the surface and applying a cap, you can successfully cap any copper pipe until it's needed again. The simplest way of achieving this repair is by using a cap that uses compression, not solder or threaded fittings, on the end of the damaged pipe.

    Shut off the main water line by turning the main water shut-off valve clockwise.

    Locate the damaged pipe and mark it 1 inch below where the damage is located, or at any point below the damage where you want to cap the line, using a felt-tipped pen.

    Place a pipe-cutting tool on the mark and rotate the tool clockwise, making sure to tighten the blade every rotation until the damaged section of pipe snaps cleanly off.

    Use a fine-grit sandpaper to polish the end of the pipe. Vigorously rub the sandpaper over the final 2 inches of the pipe, including the lip of the cut pipe to remove burrs. The sanded pipe should shine when finished.

    Align a push-to-fit pipe cap over the end of the pipe. Press the cap firmly over the pipe until it will not go any further. Compression bands within the cap will create a watertight semi-permanent seal.



    • Push-to-fit caps can be removed, but require a special tool available from the manufacturer of the cap at most home-improvement stores.


    • Cut copper pipe can be sharp, so handle it with care.

    Writer Bio

    Heath Roberts has worked as a professional reporter for several Colorado newspapers. He has covered breaking news and features for the "Denver Post" and other local publications. Roberts holds Bachelor of Arts degrees in both journalism and political science.


    Off water line cap

    How to Turn Off and Cap a Water Line Properly

    This guide will explain how to turn off the water to your home and how to cap the water line.

    This is something you will have to do before beginning any demolition or construction project in your home, in your garage, or anywhere that water is fed.

    How to Turn Off the Water Supply:

    1. Locate the main shut-off valve.

    The main water shut-off valve is typically a brass valve with a round handle and is located near the main water pipe leading into your home.

    This pipe is often in the basement, kitchen, or utility room. In regions where it’s warm year-round, the shut-off valve may be outside.

    2. Turn off the valve.

    Turn the valve clockwise to turn off the water.

    Once the water is shut off, the appliances that use water won’t work properly until the water is turned on again.

    Avoid using the dishwasher, washer and other appliances while the water is shut off to avoid causing damage.

    3. Drain residual water from the pipes.

    Turn on the faucet in your basement washtub or an outside spigot to remove as much water from the pipes as possible.

    How to Cap the Water Line:

    1. Cut off the water pipes.

    Use a tubing cutter or hacksaw to make a clean square cut, cutting the least amount of pipe as possible.

    Then, wipe the ends of each cut pipe with a cloth to ensure they are smooth and clean.

    2. Cap the pipes.

    Place the cap on the pipe and make a “depth mark.”

    Then, push the pipe cap onto the pipe until its edge lines up with your depth mark. 

    3. Test the cap’s fit.

    Turn the water back on and check to see if there are any leaks at the cap’s connections.

    If you don’t observe any water dripping, there are no leaks, and the cap is installed correctly.

    If you do see dripping, repeat step five until there is no leak.


    Keep reading:

    How To Cap A Copper Water Supply Pipe

    How to Cap Water Pipes With Push-to-Connect Fittings


    • Emery cloth (if needed)
    • Push-to-connect pipe caps
    1. Shut Off the Water

      Shut off the water supply to the house. Since you'll be cutting the water pipes behind or below the shutoff valve on each pipe, you must shut off the water at the main shutoff valve.

      Drain residual water and pressure from the pipes by turning on an outside spigot or a faucet that is lower than the pipes you are working on (such as on a basement washtub). This minimizes the amount of water that spills out of the pipes when you cut into them.

    2. Cut Off the Pipes

      Cut off the water pipes, using a tubing cutter if you have enough room to rotate the tool around the pipe. You can also use a hacksaw, but be careful to make a clean, square cut to ensure a proper seal with the push-to-connect caps. Leave as much pipe as possible so you won't have to add an extension later when reconnecting the fixture.

    3. Clean the Pipe Ends

      Clean the end of each cut pipe with a rag. It must be smooth and free of old solder or other material. If you cut the pipes with a hacksaw, file off any rough edges before cleaning. If necessary, you can smooth rough surfaces with emery cloth, but be careful not to sand down the pipe; it should have its original roundness and diameter to ensure a proper seal with the push-to-connect fitting.

    4. Cap the Pipes

      Measure from the end of each pipe and make a depth marking, as directed by the push-to-connect fitting manufacturer. The mark will tell you when the fitting is pushed on all the way, which is essential for a proper seal.

      Push the pipe cap onto the pipe until its edge reaches the depth mark.


      Push-to-connect hardware works for copper, CPVC, and PEX water pipe. Most include a stiffener—a small plastic cylinder—that slips into the end of the pipe to provide rigidity when you are capping PEX tubing. The stiffener is not required with copper or CPVC pipe.

    5. Test the Capped Fittings

      Turn the water back on and check the cap connections for leaks.

      Push-to-connect fittings can be temporary or permanent. Most include a release feature that allows you to remove the fitting with a special tool, which is usually a simple plastic device that you push against the fitting to depress a release collar and slip off the fitting. Always use the manufacturer's tool to remove the fittings.

    Copper vs. PEX and Push-Fit SharkBite Comparison


    Now discussing:

    How To: Cap off a water pipe

    Watch this video to learn how to cap off a water pipe with a push fit fitting within seconds. Useful for when you absolutely have to cut a pipe.

    1. Put an insert firmly into the pipe.
    2. Push the fitting onto the pipe.
    3. To take if off, just push on the collar and pull it off the pipe. Make sure there's no water running through it!

    The push fit fitting is easy and reliable in emergencies when you have to cut a pipe.

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