Why Do I Get Air Hissing in My Water Pipes?

Besides being annoying to listen to, hissing sounds emanating from water pipes are signs of water leaks. Find the location of the sound and repair the pipes as needed to avoid flushing what could be thousands of gallons of water downstream.

Close-up of plumbing outdoors
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Pinpoint and rectify the noise issue as quickly as possible.

Hissing Noise Definition

Water pipes that make a hiss or whoosh sound are indicative of water leaks. Listening for such sounds is the best way to determine if pipes are leaking. The hissing can sound like constant static noise and is the only type of sound you will hear when dealing with pipes featuring 30 psi or higher water pressure. Other water leak sounds, such as splashing, beating, thumping or clinking, may accompany hissing and whooshing sounds depending on pipe material and other factors, though they are usually not as loud.

Reasons for Hissing

Numerous factors influence hissing and other sounds of leaking water pipes, such as the water pressure inside a pipe. Other factors include the type of pipe material used. For example, metal pipes, such as those made from iron, steel or copper, all create louder, higher-frequency noises than do pipes made of PVC or asbestos. Pipe diameter is another consideration because smaller pipes result in louder sounds than do larger pipes. The kind of soil used over piping and how well it is compacted are also factors. Sandy and very loose soils do not transmit sound well, particularly if over newly buried pipelines. High-moisture soils, such as those in swamps, transmit sound poorly. Hard, compacted soil transmits sound the best. Whether the pipe is buried under grass, asphalt, loose dirt or concrete slab is the final factor. Grass and dirt feature surface variations that make sound transmission difficult, while concrete and asphalt provide surfaces for sound that resonate well.

Pinpointing the Hissing

Pinpointing the hissing sound for repair requires finding the location of the pipes on the street with a pipe and cable locator and then marking the location. The sound is generally loudest in piping between the valve or hydrant. It is the second-loudest section of line you must mark, however. Use a ground microphone to locate this spot exactly. Hire a professional to fix or replace the piping if needed.

Leak Facts and Tips

It is important to fix water leaks for water conservation purposes. For example, an 1/8-inch hole in a 40 psi metal pipe leaks 2,500 gallons of water in 24 hours. A leaking toilet can use as much as 90,000 gallons of water in a month. Watch for leaks by being aware of the signs and symptoms of leaky pipes, and wrap exposed pipes during cold weather to avoid breakage. Check your sinks for drips and your toilets for leaks, and replace old appliances as needed with energy-efficient models.