How to Repair a Slow Leak on a Copper Fitting Pipe

Written by finn mccuhil
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How to Repair a Slow Leak on a Copper Fitting Pipe
A slow leak in your copper plumbing should be repaired immediately. (plumbing image by Inger Anne Hulbækdal from

A slow leak in a copper fitting can not only increase your utility bill, excessive moisture from the leak can also cause structural damage to your home. At the very least, a spot in your house exposed to constant moisture makes an ideal breeding ground for mould, fungus and bacteria. Repairing a small leak in copper plumbing is relatively easy and should be done as soon as it is noticed.

Skill level:

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Things you need

  • Propane torch
  • Adjustable pliers
  • Round wire tubing brush
  • Sandpaper
  • Soldering paste
  • Silver solder
  • Cotton Rag
  • Coffee can or similar sized container
  • Water

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  1. 1

    Turn off your main water supply. For houses on municipal water supplies, this valve is located on or neat the water meter. If your water is supplied by a well, the main cut-off should be located on or near the bottom of your pressure tank.

  2. 2

    Drain the water from your plumbing. Open all the faucets in your house and allow them to drain. The presence of water in a copper pipe will prevent it from becoming hot enough to melt solder.

  3. 3

    Remove the leaking fitting. Heat the fitting with a propane torch. Grasp the adjoining pipe gently but firmly with adjustable pliers and pull. When the fitting is heated sufficiently, the solder will melt and the pipe will pull free of the fitting with only a small amount of force.

  4. 4

    Allow the fitting to cool.

  5. 5

    Clean the inside of the fitting with a round wire brush. Insert the brush into the fitting and twist it several times. Remove the brush and inspect the inside of the fitting. Repeat the brushing as necessary until the inside of the fitting is uniformly shiny.

  6. 6

    Sand the outside of the pipe with fine grade sandpaper. Remove as much old solder as possible. Continue sanding until the surface is clean and smooth.

  7. 7

    Apply soldering paste to the inside of the fitting and the outside of the pipe. Place the end of the pipe back into the fitting.

  8. 8

    Unroll and straighten 6 inches of silver solder wire off the coil.

  9. 9

    Heat the fitting with a propane torch. Hold the end of the solder on the pipe at the edge of the fitting. When the pipe is heated to the melting point of the solder, the solder will flow into and fill the joint. Place a coffee can half-full of water underneath the joint to reduce the risk of fire or accidental damage to the surface underneath your work area. If there is not enough clearance underneath the pipe to fit a coffee can, a damp cotton rag can be used.

  10. 10

    Turn the torch off and allow the joint to cool at least 10 minutes before turning the water back on.

  11. 11

    Turn the water supply on and inspect the fitting for leaks. If you are new at sweating copper, this may take more than one try.

Tips and warnings

  • Apply heat to the fitting, not to the pipe. Solder will flow in the direction of the heat.
  • The pipes and fittings will be extremely hot during and after sweating. Do not handle the surrounding plumbing with your bare hands until the pipes have cooled.
  • Do not cool fittings by dousing them with water. Fast quenching can cause the structure of the copper to become brittle or deform.
  • Copper is a soft metal. Applying too much force with pliers can deform your fittings and pipes making them difficult to fit back together.

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