Why Does My Hot Water Smell Like Rotten Eggs?

Published: July 14, 2026

You turn on the shower and instead of clean-smelling steam, you get a whiff of rotten eggs. It's unpleasant, embarrassing, and worrying — but the good news is that it's one of the most common water heater problems, and it's almost always fixable at home. Here's what causes that sulfur smell and how to get rid of it for good.

What Causes the Rotten Egg Smell?

The smell comes from hydrogen sulfide gas, which forms when bacteria in your water heater react with sulfur minerals in the water. Water heaters create the perfect environment for these bacteria: warm temperatures and a little sediment to feed on. The bacteria multiply, produce the gas, and your hot water starts smelling like a science experiment.

Certain conditions make it worse:

• Well water: Contains more sulfur and bacteria than municipal water
• Infrequent use: Long idle periods let bacteria thrive
• Low temperature settings: Below 120°F, bacteria grow more easily
• Aged anode rod: A corroded rod feeds the bacteria

Is It Dangerous?

In most cases, no. The hydrogen sulfide levels in household hot water are usually far below harmful concentrations. It's more of a nuisance than a health issue. However, there's one important exception: if you have a gas water heater, a rotten egg smell could occasionally indicate a gas leak (gas companies add sulfur compounds to natural gas precisely so leaks are detectable). If the smell is strongest near the water heater itself rather than at the faucet, shut off the gas, open windows, leave the house, and call your gas utility immediately.

First Step: Confirm It's the Water Heater, Not the Water

Run both the hot and cold taps. If only the hot water smells, the source is inside your water heater. If both smell, the problem is your water supply or well — and no amount of water heater maintenance will fix that.

How to Fix Smelly Hot Water: Step by Step

1. Raise the Temperature Temporarily

Set your water heater to 140°F for 24-48 hours. The heat kills the bacteria. Afterwards, remember to set it back down to a safe, energy-efficient setting — 120°F is the sweet spot. Just be careful: the water will be hot enough to scald during this period, so warn everyone in the household.

2. Flush the Tank Thoroughly

Sediment is food for the bacteria, so removing it is key. Follow our full guide on how to flush your water heater — the process takes about an hour and also improves efficiency. A complete flush removes the slimy biofilm bacteria need to survive.

3. Shock the Tank with Hydrogen Peroxide

For stubborn smells, pour about two cups of hydrogen peroxide (3%) into the tank through the hot water outlet or the anode rod opening, refill the tank, and let it sit for a few hours before flushing. Hydrogen peroxide is safe for your plumbing and destroys the bacteria without the harsh effects of chlorine bleach.

Some plumbers use a chlorine bleach shock instead, especially on well systems. It works, but bleach can leave a chemical taste and, in high concentrations, stress the tank's anode rod. Peroxide is the gentler option for routine cleaning — save the bleach for sanitizing a brand-new or heavily contaminated well system, and follow the manufacturer's directions carefully.

4. Replace a Worn Anode Rod

An old magnesium anode rod is a magnet for odor-causing bacteria. Swapping it for an aluminum or powered anode rod frequently eliminates the smell permanently. Our guide on anode rod replacement walks you through the whole job.

5. Don't Let the Tank Sit Idle

If you're away for a week or more, the stagnant warm water is a bacteria paradise. When you return, run the hot water for several minutes before showering, or do a quick flush to clear things out.

Preventing the Smell Long-Term

• Keep your thermostat at 120°F or slightly higher
• Flush the tank twice a year, especially on well water
• Replace the anode rod every 3-5 years
• Run hot water at least once a week if the home is lightly used

These steps overlap heavily with good general upkeep — see our water heater maintenance tips for the full routine.

When to Call a Professional

If you've flushed the tank, raised the temperature, and replaced the anode rod but the smell persists, you may have a deeper issue like a reaction inside the tank or a water supply problem. That's when an experienced technician is worth the call. A pro can sanitize the system properly, test the water, and check for sediment damage that's already been done. Find water heater repair services near you, or see if we cover your area — and don't put up with smelly showers a day longer than you have to.