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Plumbing problem
Why is my water heater making noise?
The short answer
Rheem, a water heater manufacturer, ties each sound to a different cause. Popping and rumbling point to sediment at the bottom of a tank. Ticking and humming are normal operation. Hissing or sizzling means shut the unit off and get it inspected (Rheem). The sound, plus whether it happens while the unit is heating, is the most useful thing to tell a plumber.
What people usually report
A popping or crackling sound while the burner or element is on, a deep rumble, a knock in the pipes when a faucet shuts off, or a high whistle. Some notice the noise got louder over months; others notice it after a plumbing repair or a change in water pressure.
What the manufacturer says each sound can mean
| Sound | What it can mean | Suggested action |
|---|---|---|
| Popping or rumbling | Sediment buildup in tank-style units, as water heats beneath the debris. | Annual flushing; professional service for extreme buildup. |
| Hissing or sizzling | Water dripping onto a hot burner (gas) or a leaking heating element gasket (electric). | Turn off power or gas, avoid using the system, and schedule a professional inspection immediately. |
| Knocking or banging | Water hammer, when flowing water suddenly stops or changes direction. | Water hammer arrestor, adjusting water pressure, securing loose piping. |
| Screeching or whistling | Restricted flow or pressure irregularities: closed valves, a faulty T&P valve, or sediment. | Make sure valves are fully open, check pressure, replace worn parts. |
| Ticking | Heat traps or pipe expansion as temperatures change. | Normal operation; no action needed. |
| Humming | Common in electric units when the heating elements are on. | Normal operation; no action needed. |
Source: Rheem (water heater manufacturer). Follow your own heater’s manual where it differs.
Where the sediment comes from
USGS defines water hardness as generally the amount of dissolved calcium and magnesium in water, and says hard water heated in appliances leaves solid deposits of calcium carbonate that can lower a water heater’s efficiency (USGS). Cambridge’s water department lists iron, magnesium, and calcium among the sediments that build up in the bottom of a water heater (Cambridge (MA) Water Department).
Water hardness in some of the cities our cost pages cover
| City | Hardness (grains per gallon) | Source |
|---|---|---|
| Austin, TX | 4.1 to 7.4 (average 5.4) | Austin Water 2025 Annual Water Quality Report (Consumer Confidence Report), p. 4 — hardness 70 to 126 ppm [4.1 to 7.4 gpg], average 93 ppm [5.4 gpg] |
| Jacksonville, FL | about 15 | JEA 2025 water-quality data (about 15 gpg / 256 ppm) via HardWaterHQ |
| Las Vegas, NV | 16 to 17 | Las Vegas Valley Water District, water quality FAQs (291 ppm / 17 gpg, "very hard") |
| San Antonio, TX | 15 to 20 | SAWS water-quality FAQ (hardness 15-20 gpg) |
| Tampa, FL | about 11 | City of Tampa annual water-quality data (about 186 ppm / 10.9 gpg) via DROP Connect |
Figures come from our city data layer; see how city data is sourced.
How to find out
- Name the sound. Match it to the table above, and note whether it happens only while the unit is heating.
- Look, without opening anything. Check for water on the floor, at the connections, or at the relief valve pipe. If you find water, start with what a leaking water heater means.
- Check the temperature setting. The U.S. Consumer Product Safety Commission urges setting water heaters to 120°F to prevent scalds, and notes most adults suffer third-degree burns from two seconds of 150°F water (CPSC).
- Flushing. The City of Thornton’s flushing instructions (City of Thornton, CO) show what the job involves: water and power or gas off, a hose on the drain valve, and repeated draining until the water runs clear. Thornton says to consult a plumber with any questions.
Age matters for the repair-or-replace decision. Our 135 rule page explains the rule of thumb, and water heater replacement cost has the cited price ranges. No hot water at all is a separate problem: see no hot water.
Local help
Who to contact
If you are on a public water system, your water utility is the first call for anything that affects the water itself. Its phone number is on your bill and in its annual water quality report.
For work on the pipes and fixtures inside your home, hire a licensed plumber and confirm the license before work starts. Our guide to choosing a plumber covers what to ask. License lookups for the areas our city pages cover:
- FL: Florida Department of Business and Professional Regulation (DBPR)
- IA: Iowa Plumbing and Mechanical Systems Board (PMSB), administered by Iowa DIAL
- MO: Kansas City, MO City Planning & Development (plumbing license, city-issued)
- NE: City of Omaha Building and Development Division (plumbing license, city-issued; Nebraska has no statewide plumbing board)
- NV: Nevada State Contractors Board (NSCB), Classification C (plumbing)
- OK: Oklahoma Construction Industries Board (CIB)
- TX: Texas State Board of Plumbing Examiners (TSBPE)
Elsewhere, search your state’s plumbing or contractor licensing board. Some cities issue plumbing licenses themselves.
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Is this covered by a home warranty?
A home warranty is an annual service contract that pays to repair or replace covered home systems and appliances when they fail from normal use, in exchange for a monthly premium and a fixed service fee per visit. It does not cover a failure that has already happened or a fault that existed before the plan started, so it only helps if it is in place before the breakdown.
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Related costs and guides
Common questions
Water heater noise questions
Should I be worried if my water heater is making noise?
It depends on the sound. Rheem, a water heater manufacturer, describes ticking and humming as normal operation, popping and rumbling as sediment buildup in tank-style units, and hissing or sizzling as water dripping onto a hot burner on gas models or a leaking element gasket on electric models. For hissing or sizzling, Rheem says to turn off the power or gas, avoid using the system, and schedule a professional inspection immediately.
How do I stop my water heater from making noise?
For popping and rumbling, Rheem recommends flushing the tank once a year and professional service for extreme buildup. City water departments in Thornton, Colorado and Cambridge, Massachusetts publish step-by-step flushing instructions. For knocking or banging, Rheem points to water hammer and lists a water hammer arrestor, adjusting water pressure, and securing loose piping.
Why does my water heater sound like a tea kettle?
Rheem groups screeching and whistling together and links them to restricted water flow or pressure irregularities, from a closed valve, a faulty temperature and pressure relief valve, or sediment. Its suggested checks are making sure valves are fully open, checking pressure levels, and replacing worn parts.
Sources and limits
- Rheem (water heater manufacturer), The Ultimate Guide to Water Heater Noises: What's Normal (and What Isn't). Checked 2026-10-05.
- Fire Department of the City of New York (FDNY), Natural Gas Safety: If you think you smell gas or suspect a gas leak. Checked 2026-10-05.
- U.S. Consumer Product Safety Commission, Avoiding Tap Water Scalds (Publication 5098). Checked 2026-10-05.
- U.S. Geological Survey, Hardness of Water. Checked 2026-10-05.
- City of Thornton, CO, Tips for Flushing Your Home Water Heater. Checked 2026-10-05.
- Cambridge (MA) Water Department, How to Flush Your Hot Water Heater. Checked 2026-10-05.
This page summarizes guidance published by the agencies and organizations listed above. It is general information, not a diagnosis of your home or your water. Guidance can change, so check the linked source, your water utility, or your local health department before acting on it. PlumbingRepairCost is not affiliated with any agency named here. Spotted an error? Email hello@plumbingrepaircost.com and we will check it against the source.