Loud Steam Piping

You may be familiar with older churches where the walls ping and ding in the winter while the heat is on. At times it might even sound more like someone is hitting the pipes with a hammer! People may tell you that it's normal in steam heat or that it is the noise of the metal expanding. That is not the case.

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A properly designed and maintained steam system is almost completely silent, quieter even than a furnace. What causes these loud bangs and slams is either improperly pitched radiators or, more commonly, broken traps.

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An improperly pitched radiator will struggle to flow water and steam in the same pipe. This will cause the water to be "caught" by the steam and hurled into the end of the pipe.

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A similar thing is happening with a failed trap. The returns in a 2-pipe steam system should only ever have air or water in them. Traps are installed at the end of each radiator. They are designed to close at 212F, the temperature of steam. As the radiator radiates heat out the steam begins to condense into water again. As this happens the temperature of the condensed water(condensate) drops as well. Once that temperature reaches about 180F the trap opens and allows water into the return so that it flows back into the boiler. 

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If a trap fails open the steam and water both flow through the trap into the return, this causes both steam and water hammer in the return which is inefficient and can cause further damage.