Plumbing, Heating and Pool Repair Guides

How Steam Traps Work


WeT HeaD KnowledgeThe term “steam trap” might have confused you a bit when first hearing it used, if you have never heard the term before or the term could scare the heck out of you if your a building owner and the service company told you that you need to replace all your steam traps in your building because there were all failing, but either way you have landed here and want to know “how steam traps work”. Steam traps work by collecting the steam that has now turned into “condensation” and then returning it back to the steam boiler with gravity and condensation pumps.There are a few different types of steam traps and depending on what type we are talking about will determine exactly how each does work.

The “F&T steam trap” called F & T for short is also know as a “float and thermostat” trap and works with a float and a thermostat the opens at a certain temperature so the water can return to the boiler.The “cage unit steam trap” work in almost the same way but it does not use a float, instead it uses a spring and a thermostat and also opens when the temperature that is set by the thermostat is met. You might be wondering at this point, “what type of steam traps do I have” and the question to that can not be answered by this article alone but here is a few places each type of steam trap can be found in. F & T steam traps are usually located in boiler rooms, inside crawl space and high in ceilings. These types of traps are more main line traps and you generally won’t find them in areas that are occupied as living or common space. F &T traps are more of the behind the scene muscle traps that support the steam network.

The Steam trap know as the “cage unit” is commonly found in radiators inside areas that are or will be occupied by people. These case unit traps are often replaced by heating professionals thinking that will be the fix, and not realizing the they have F & T traps below on the main lines, causing the new cage units to fail. There are many companies that make steam traps and replacement parts or rebuild kits for steam traps. Some of the most popular manufacturers of steam traps are:

  • Armstrong Steam Traps
  • Spirax Sarco
  • Barnes & Jones

These are just a few of the main stream names of companies that are well know in the steam trap industry.It is always best to hire a licensed professional that is qualified in steam trap repair and maintenance to repair your steam system as there is a lot involved.


  1. We have a WHRB along with super heater and turbine generator sections. We have mechanical steam traps in our boiler section.I want to know how de we calculate the efficiency of steam traps. One of the answers to this could be to provide a mechanical drain valve after some length of the steam line after the trap. Pls. provide me any other solution to this question.

    Sterlite Industries India Ltd.

  2. Amazing steam showers, we had one of these built around 5 years ago but
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