Why Your Tucson Water Smells Like Rotten Eggs

You turn on the tap, and it hits you: rotten eggs. It's a smell most Tucson homeowners run into at some point, and it almost always points to hydrogen sulfide gas reacting with bacteria or metal somewhere in your plumbing system. The good news is that it's rarely dangerous. The better news is that with a few quick tests, you can usually narrow down the cause in under five minutes.

Step One: Figure Out Where the Smell Is Coming From

Before you call anyone, do this test. Run cold water at a bathroom sink for 30 seconds and smell it. Then run hot water and smell it. Then check another fixture in a different part of the house. The pattern tells you almost everything.

• →Only hot water smells: the problem is almost certainly inside your water heater.
• →Only one fixture smells: bacteria or buildup is trapped in that drain or P-trap.
• →Cold and hot water at every fixture smells: the issue is in your supply line or, less often, the Tucson Water source itself.
• →Smell hits when water sits overnight but disappears after running: bacterial growth in low-flow lines.

The Water Heater Culprit (Most Common in Tucson)

Most Tucson water heaters come with a magnesium anode rod. Combine that magnesium with our mineral-heavy water (550+ TDS) and the sulfate-reducing bacteria that thrive in warm tanks, and you get hydrogen sulfide gas. That's your rotten egg smell. It's especially common in vacation homes, guest bathrooms, or any tank that sits unused for days at a time.

The fix is usually swapping the magnesium anode rod for an aluminum-zinc rod and flushing the tank. If your heater is more than 10 years old and already showing signs of sediment buildup or corrosion, replacement may make more sense than another round of repairs.

When It's the Drain, Not the Water

Here's a trick: fill a glass with water from the smelly faucet, then walk into another room and smell it. If the water in the glass smells fine, the odor was coming from the drain, not the water. Tucson's dry climate means P-traps in guest bathrooms evaporate faster than you'd expect, letting sewer gas drift up through the drain. Pouring a cup of water down unused drains once a week solves it.

If the drain still smells after refilling the trap, you likely have biofilm buildup in the pipe. A mix of baking soda followed by vinegar, left to sit 15 minutes, then flushed with hot water, clears most of it. Persistent smells usually mean buildup deeper in the line.

When the Problem Is the Supply Line

If every faucet in the house smells — hot and cold — and the smell shows up in a glass of water away from the sink, the issue is in your supply line. For homes on Tucson Water, this is rare but does happen after main breaks or hydrant flushing in your area. For homes on a private well in Pima County, sulfur bacteria in the well itself is a common cause and usually requires shock chlorination and sometimes a whole-house treatment system.

What Not to Ignore

A rotten egg smell paired with discolored water, a metallic taste, or visible corrosion on fixtures points to something bigger than bacteria — usually a deteriorating water heater, failing galvanized pipes, or a cross-connection issue. Tucson's hard water accelerates all of these. If you're seeing any combination of those signs, get it looked at before a pinhole leak turns into slab damage.