Water Heater Noises: Popping, Rumbling, Whistling and What They Mean
By Mike Holt, NJ Master Plumber · November 1, 2026 · 3 min read · Updated November 1, 2026
Quick answer
Popping or rumbling usually means mineral sediment at the bottom of the tank; water trapped under it boils and bursts through. A professional flush often quiets it. Hissing can be a drip on the burner or the relief valve letting off pressure. Whistling often means a valve that's partly closed. Ticking and light humming are usually normal.
- Difficulty
- Listen and look. Flushing and repairs need a professional
- Time
- About 10 minutes
- You need
- Flashlight
Rather not risk it? A licensed plumber can handle this for you, with written upfront flat-rate pricing options before any work starts.
Smell gas, or the relief valve is spraying? If you smell gas, leave immediately and call 911 and your gas utility from outdoors. If the relief valve is spraying, keep clear of the hot water, close the cold water valve if you can reach it from a dry spot, and call us. 908-873-6686
Most water heater noises come from one of three things: sediment at the bottom of the tank, water moving through a valve that's partly closed, or metal expanding as it heats. The sound tells you which one, and that helps you decide what to do next and what to tell your plumber.
What is your water heater noise telling you?
| Noise | Usual cause | What to do |
|---|---|---|
| Popping, rumbling, crackling | Sediment on the tank bottom; water under it boils into steam | Have the tank serviced |
| Hissing or sizzling (gas) | Water dripping onto the burner, from condensation or a leak | Look for water under the tank; call if it's a leak |
| Hissing or sizzling (electric) | Sediment building up around the lower heating element | Have the tank serviced |
| Whistling or screeching | A valve that's partly closed, or the relief valve letting off pressure | Call; a plumber checks the valves and the pressure |
| Ticking or tapping | Pipes and heat traps expanding as they warm and cool | Normal |
| Humming (electric) | Water flowing past the heating element | Normal unless it's loud or smells hot |
| Banging when a faucet shuts off | Water hammer or high pressure in the pipes | Have the pressure and the expansion tank checked |
| Boom when the burner lights | Delayed ignition on a gas burner | Call a plumber; don't relight it |
How to narrow down the noise
Step 1: Find where the noise is coming from
Stand next to the heater while it runs. Noise from the bottom of the tank often means sediment. Noise from the pipes on top points to a valve or to the pipes expanding. A sound from the brass valve on the side of the tank means the relief valve, and that one needs a plumber.
Step 2: Look at the cold water valve
Find the valve on the cold water pipe going into the top of the tank. A lever that's fully open lines up with the pipe. If it looks partly closed and the heater is whistling, tell us when you call.
Step 3: Note when it happens
Does it happen only while the burner or elements run, or when a faucet shuts off? Is it new? Has the tank ever been flushed? A flush follows the manufacturer's instructions and involves scalding water and an aging drain valve, so ask us rather than opening the valve. Our water heater flushing guide explains the risks.
Step 4: Check the relief valve pipe
Look at the pipe that runs down from the brass relief valve. If it's wet or dripping, the tank may be running too hot or the pressure in the house may be too high. Don't plug or cap that pipe. See how to set your water heater temperature, and call us about the relief valve.
When a noisy water heater needs a plumber
Popping that comes back soon after a flush often means the sediment has hardened on the tank bottom and a flush can't move it. On an older tank, that can go along with rust in the hot water or a slow leak at the base, and it may mean the heater is near the end. A boom when a gas burner lights, a dripping relief valve or a gas smell is never something to live with.
We repair and replace gas and electric tank water heaters up to 50 gallons. On tankless units we do diagnostics, repairs and maintenance only, with no tankless installation or replacement. Most municipalities in Middlesex, Somerset, and Monmouth counties; Select Union, Ocean, Mercer and Hunterdon municipalities only. Contact us to confirm whether your job site is within our current service area. Written upfront flat-rate pricing options. You choose. See our water heater service or call 908-873-6686.
Get tips and reminders
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Stop and call us if
- The relief valve on the side of the tank drips, hisses or sprays.
- There's water around the base of the tank along with the noise.
- You hear a loud boom when the burner lights.
- The tank pops or rumbles every time it heats, especially if it's old and has never been flushed.
- The noise started along with rusty water, a rotten-egg smell or no hot water.
Call 908-873-6686.
Michael Holt
Owner and operator of Plumbing Doctor, NJ Master Plumber (Lic. #36BI01345600) and U.S. Marine Corps veteran.
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