How to Patch Radiator Pipes

Updated May 18, 2018

Radiant heat systems are powered by a boiler that heats water and forces it through pipes to radiators installed in a line through the home. The radiators then radiate the heat from the water into the rooms. Radiator pipes can crack or leak when they age, usually because of rust forming inside the pipes. Patching a radiator pipe with liquid steel epoxy involves draining the radiator system first.

Turn the boiler off. Allow the system to cool for about two hours. Turn off the circuit breaker to the radiator. Turn off the water supply line to the radiator by turning the valve clockwise.

Screw a garden hose onto the boiler base at the drain outlet. String the hose to a sink or outdoors. Turn the drain valve counterclockwise to open it. Open the bleed screw on top of the radiator that is the last one in the line for the home, or in the highest position in the house.

Open the bleed screw on the radiator that is closest to the boiler. Water will drain from the system down the hose and into the sink, drain or outdoors through the garden hose.

Pour acetone on a shop towel and use it to thoroughly clean the radiator pipe that needs patching. Scuff up the surface by working a metal file back and forth over the area.

Pour both tubes of the liquid steel epoxy on a paper plate. Mix them together thoroughly with a plastic knife. Spread a very thin layer on the radiator pipe to cover the hole or crack. Extend the epoxy about 1/2 inch past the crack on all sides. Let the epoxy dry according to the package instructions.

Unscrew the garden hose. Turn the boiler drain valve clockwise to close it. Close the bleed screws on the radiators that are farthest and closest to the boiler. Turn on the circuit breaker to the boiler. Turn the boiler switch on.


An epoxy patching compound has two tubes in equal portions. One contains liquid steel resin in an epoxy base; the other contains a hardener. Mixing them together makes a liquid steel compound to match metals together. Steel epoxy patch kits are available at hardware, automotive supply and home improvement stores.


Do not use vinyl epoxy on radiator pipes. Use only a product with liquid steel.

Things You'll Need

  • Garden hose
  • Acetone
  • Shop towel
  • Metal file
  • Liquid steel epoxy
  • Paper plate
  • Plastic knife
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About the Author

Mary Lougee has been writing for over 10 years. She holds a Bachelor's Degree with a major in Management and a double minor in accounting and computer science. She loves writing about careers for busy families as well as family oriented planning, meals and activities for all ages.