Call a plumber: whistling, screeching or another odd sound

Why this happens

Rheem says whistling or screeching often means restricted water flow or pressure irregularities, such as a partly closed inlet or outlet valve, a faulty T&P valve, or mineral or sediment buildup, and that a persistent high-pitched sound usually will not clear up on its own. A. O. Smith says screeches and whistles depend on the heater type: a dirty blower wheel or blocked vent on a heater with a blower, failed blower motor bearings, or a bad heating element on an electric heater. A. O. Smith says humming is often a loose part vibrating, and Rheem says a light hum is normal on an electric heater, so a hum that is loud or new deserves a look. Bradford White says a sound outside normal operation is a reason to contact a plumbing professional.

What to do right now

1. If you smell gas, or hear hissing near a gas line or the burner, leave the house and call 911 and your gas utility from outside.
2. Rheem lists a partly closed inlet or outlet valve as one cause of whistling or screeching, and says to make sure valves are fully open. Look at the handle on the cold water valve at the heater from where you stand, but do not turn it. Someone may have set it that way on purpose, for example after a leak, and a valve that is stuck or drips must never be forced. Tell the plumber what you see.
3. Do not touch the relief valve. Do not open the heater's panels or take off the vent, and do not clean a blower yourself; leave that to the pro.
4. Write down what the sound is like, when it happens, how long it has gone on, whether it happens with no water running, and when the heater was last serviced. A. O. Smith says a pro may ask questions like these.
5. Call a licensed plumber or an authorized water heater service provider. If you see water or steam, or hear hissing or sizzling, stop using the heater and call right away, and keep away from the end of the relief valve pipe. Rheem says that if a screech keeps going, it is safest to turn the unit off and contact a professional. To turn it off, use the breaker (open only the hinged panel door) or the gas shutoff valve, by hand and never forcing it, as A. O. Smith advises for shutting off a leaking heater, and only if you are on a dry floor, nothing electrical is wet and you can reach the control without going near water or steam, because Ready.gov says not to touch electrical equipment if it is wet or if you are standing in water.

When to stop. Water or steam from the relief valve pipe means keep away from the end of the pipe, never block it, and call a licensed plumber right away. A leak under the tank, or hissing or sizzling, means stop using the heater and call a licensed plumber. Smoke, flames, sparks or a burning smell near the heater mean leave the house and call 911 from outside. A gas smell, or hissing near a gas line or the burner, means leave and call 911 and your gas utility from outside.

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