Home hot water heater and gas boiler Surging water levels can cause inefficient boiler operation and other problems. Image Credit: Comstock/Comstock/Getty Images

Surging water levels in your boiler can be caused by numerous reasons but are usually a result of excess dirt or oil in the water. The condition is characterized by quickly changing water levels, which is generally due to inefficient steam release. Debris prevents steam from adequately escaping the water, causing it to rise and drop randomly. Addressing these problems is part of routine boiler maintenance.

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Surging is simply the fluctuation of water levels in your steam boiler, which you can observe through the gauge glass. Some amount of surging is not a major concern and is relatively common. But severe surging of more than 1 inch is a problem. This can lead to inefficient boiler operation, violent water changes and the introduction of extra water into the boiler through the water feeder. Generally, a clean and well-maintained boiler will not have these problems. If your water is foaming, it may cause similar symptoms but is usually due to high pH.

Dirty Water

Dirt, sludge and other debris in your water boiler can cause surging. As the water heats up and steam bubbles are created, they have difficulty penetrating through the dirty water. This action creates a fluctuating or surging water line. Boilers can grow dirty over time and need occasional flushing.

Oily Water

A presence of oil in the boiler water is a common cause of surging. Oil is generally present on new piping and parts, so a slick of oil tends to develop on the water surface. As in the case of dirty water, the oil makes it difficult for steam bubbles to penetrate the surface. This creates a surging motion as bubbles collect under the slick and break through all at once, which creates a violent boiling situation.


Remedying a boiler surge problem depends on its cause. If the water is dirty, you need to clean out the boiler by draining and replacing the water as directed by the manufacturer. If oil is the problem, you should skim the boiler as directed in the manual. Simply draining a boiler will not remove oil because it tends to stick to the sides of the boiler. Skimming removes the water via a special valve located high on the boiler. Another option is to install a surge column to regulate fluctuating water levels.

Other Problems

There may be other reasons why the water level in your boiler fluctuates dramatically. Foaming occurs when the pH is too alkaline and can cause extreme surging. Adjust the pH, as directed by the manufacturer, to fix this problem. Undersized piping can cause steam to exit the boiler too quickly, which could also lead to surging. To avoid this, follow the manufacturer's guidelines for piping.


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