How do I join a garden tap to a copper pipe using compression coupling?

Updated February 21, 2017

Use a compression coupling, copper adaptor and a length of copper pipe to connect a garden tap to a copper water supply pipe. The compression coupling consists of a union, two brass ferrule seals and two nuts. Compression couplings don't need heat to form a joint, and you can also remove it with little effort if you need to change your household plumbing in the future. Any DIY homeowner with a working knowledge of copper pipe plumbing can perform this task in one hour with the necessary tools and materials.

Cut the copper pipe to the length required for your project using the tube cutter. Gradually increase the pressure on the cutting roller blade as you rotate it. Avoid applying too much pressure all at once as the copper pipe may become deformed during the cut.

Use the de-burring tool mounted on the tubing cutter to remove any burrs on the inside edge of the pipe after cutting.

Sand the outside of the copper pipe using emery paper up to 2.5 cm (1 inch) from the end of the pipe. Make sure you clean completely around the pipe.

Sand the inner walls of the male copper adaptor with emery paper.

Place the male copper adaptor on to the clean end of the copper pipe and check the length of the assembly to assure a proper fit prior to soldering.

Remove the pipe from the adaptor and place it snugly in a bench vice. Make sure that no flammables are near the bench vice.

Apply a small amount of water-soluble paste flux completely around the cleaned area of the copper pipe.

Install the copper pipe adaptor on to the fluxed end of the copper pipe, making certain that it is fully seated. Once seated, rotate the adaptor three-quarters of a turn to evenly distribute the paste flux between the outer surface of the pipe and the inner walls of the adaptor.

Light the propane torch and adjust the flame until it is a steady blue colour.

Concentrate the flame of the torch on the outer wall of the copper adaptor at a slight angle toward the open threaded end. In a short time, the flux will begin to boil and appear to dry up. At this point, apply the lead-free solder at the seam where the edge of the adaptor meets the surface of the pipe, rotating the solder approximately a half-turn before removing it from the heated pipe.

Allow the pipe and adaptor assembly to cool on its own. Do not rapidly cool in water or other liquids as this may cause the solder to crack.

Wrap pipe sealing tape in an anti-clockwise direction around the threaded end of the copper adaptor. This will provide a good seal for installation in the garden tap.

Connect the garden tap to the copper pipe by inserting the threaded adaptor into the tap and turning in a clockwise direction. Tighten the adaptor to the tap using an adjustable wrench.

Turn off the water valve to the copper supply line designated for the garden tap.

Sand the open end of the copper supply line and the open end of the copper pipe leading to the garden tap using emery paper. Make certain both ends of the copper pipes are even and that no bevels exist. This ensures that the pipes seat themselves properly in the compression coupler union.

Place the two compression coupler nuts on each of the copper pipes with the open threaded ends facing each other.

Place a ferrule seal ring -- sometimes called an olive -- over the end of each pipe.

Install each end of the two copper pipes into their respective end of the compression coupler union until both are fully seated. Hand tighten each of the nuts to the union as firmly as possible. Turn the nuts in a clockwise direction.

Tighten the compression nuts one at a time using two adjustable wrenches. Use one to hold the coupler union and the other to tighten the compression nut one full turn beyond hand tight. This compresses the ferrule ring into the pipe, creating a watertight seal.

Allow the garden tap and the new water pipe to flush for 15 to 30 seconds.


Always replace used compression couplings with new ones.


Work safely when using propane torches. Make certain that the work area is clear of debris and flammable materials.

Things You'll Need

  • Copper tube cutter
  • 1.25 cm (1/2 inch) thick copper pipe
  • 1.25 cm (1/2 inch) male copper pipe adaptor
  • Emery paper
  • Bench vice
  • Propane soldering torch
  • Water soluble paste flux
  • Lead-free solder
  • Pipe sealing tape
  • Garden tap
  • 1.25 cm (1/2 inch) compression coupling
  • Adjustable wrenches
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About the Author

Max Stout began writing in 2000 and started focusing primarily on non-fiction articles in 2008. Now retired, Stout writes technical articles with a focus on home improvement and maintenance. Previously, he has worked in the vocational trades such as automotive, home construction, residential plumbing and electric, and industrial wire and cable. Max also earned a degree of biblical metaphysician from Trinity Seminars Ministry Academy.