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How to Diagnose Leaks in a Steam Boiler

Ask This Old House plumbing and heating expert Richard Trethewey helps locate the leak on a steam boiler that is losing water

In this video, Ask This Old House plumbing and heating expert Richard Trethewey helps locate the leak on a steam boiler that is losing water.

Steps for Diagnosing Steam Boiler Leaks

  1. Set the thermostat at a high temperature to turn on the boiler, and leave it running during diagnosis.
  2. Once the boiler has turned on, check the floor around the boiler. This would indicate a leak on the water side of the boiler.
  3. Check all exposed piping, especially at the joints for a leak.
  4. Check the main vent of the system to locate a leak.
  5. If there are no leaks near the boiler, check the radiators in each room. Look for signs of water around the hand valve, at the connection of the steam pipe to the radiator, and at the air vent on each radiator.
  6. If there are no obvious places where water is leaking, shut off the boiler and allow it to cool. When the boiler has cooled down, remove the vent pipe and inspect the inside for any corrosion on the boiler itself.
  7. Work with a qualified plumber or HVAC technician to repair any damaged or leaking areas.

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