How to Fix a Noisy Steam Pipe

Steam systems are one of the most popular and cost effective heating systems for large buildings. However, while they put out ample heat for little energy cost, steam systems suffer one common problem: noise. Many of these systems create a knocking or vibrating noise in the lines that can drive people crazy.

There are several possible causes for this. To understand them, it's important to know that a steam heat system has two lines: steam lines that pipe hot steam up, and a condensate system that returns the cooled, condensed water to the heater. In many cases, the problem lies between these two lines. Here are some possible fixes:

Solution #1: Reduce the Pressure

The steam in a heating system does not really need to be under a great deal of pressure – just enough to circulate up the pipes and through the building. Check your steam pressure to see what setting it's on. If it's higher than 2 PSI, drop the pressure down to 2 and see what happens. Most likely, the knocking sounds will stop and the problem will be solved. Plus, you'll use less energy. This is always the first thing you should check because there is no cost to trying this repair.

Solution #2: Replace Sagging Pipes

Condensate systems rely on gravity to return the condensed water back to the steam unit. While steam pressure brings the steam up, only gravity brings it down. That means that if a pipe is sagging from old age, it can cause a backup of water. The water sits in the pipe until there is enough pressure in the line to force it on, which is noisy. Look for and replace sagging pipes in the condensate system.

Solution #3: Unclog Pipes


Pipes get old, and old pipes get dirty and can fill with rust or general grime. If the condensate lines are clogged, you will get a backup, which knocks or hammers when there is finally enough pressure to force water through. In this case, the lines need to be cleaned or even replaced.

Solution #4: Replace Bad Steam Traps

A two-line steam system has a trap that prevents hot steam from getting into the condensate system. If these traps are broken, then steam shoots into the condensate lines, forcing the condensate back and creating a noisy pounding effect. Fixing this will require replacing the steam traps completely but once done, the problem will be solved for many years to come.

Have you had other problems with a steam system? How did you fix them?

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