How to Find a Leak in Your Heating System

Updated February 21, 2017

A leak in a home's central heating system can cause the system to lose pressure. Even a small leak can cause significant reductions in system pressure. No matter the size, it is important to find and repair the leak.

Fill the water heater with water. Test the system to find out how long it takes to depressurise. This will indicate the size of the leak.

Examine the hot water heater, looking for any visual damage. Begin with the boiler, examining all fittings and pipes. Remove any covers to get a better view. Follow the pipe that comes directly out of the water heater until the point it re-enters the boiler. Continue to look for any visible signs of leaks.

Place a sheet of paper, preferably coloured, underneath the water heater. Wait for a few hours to see if any water spots appear. If water spots do appear, try to find the source of the water.

Feel along each pipe carefully, looking for any possible blockages. A cold spot on the pipe indicates a blockage in the heating system.

Check the pipe that enters the thermo valve, which is along the boiler's radiator. If the radiator is cool to the touch, but the pipe is hot, one of the radiator's valves is not working correctly.

Call a plumbing or heating and air-conditioning company to remove the pipe and flush it out. If necessary, such a company can also replace the pipe.


If, after examining the hot water heater, no leaks are visible, it is possible that the leak is elsewhere. These leaks might not be visible on older heating systems. Contact a plumping or heating and air-conditioning company to further examine the heating system. If the entire pipe is cold, the coldest portion along the pipe could indicate a blockage.

Things You'll Need

  • Sheet of coloured paper
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