If the hot tap in your Washington home smells like sulfur, rotten eggs, or scorched metal, but the cold tap seems fine, the problem is usually in the water heater or the hot water line rather than the supply. Start with a simple comparison before you change anything.
Compare hot and cold at the same sink
Run the cold tap for a minute, then smell a glass of cold water. Next, run the hot tap the same way and smell that glass. Write down what you notice at each. If both smell, the issue is more likely in the supply, which means checking the source, whether that is a well, a city line, or a filter in between. If only the hot side smells, keep going.
Check which hot taps smell
Test several hot taps, such as the kitchen, a bathroom, the laundry tub, and any outdoor spigot that is hot-fed. If every hot tap has the odor, the cause is likely at the heater. If only one fixture smells, look at that fixture, its aerator, and the short run of pipe feeding it.
Common causes to consider
- A reaction inside the water heater tank, where the metal anode rod can interact with bacteria in the water and produce a sulfur smell in hot water only.
- Hydrogen sulfide already present in the source that becomes more noticeable once it is heated.
- Sediment or slime that has built up in a tank that has not been drained or flushed for a long time.
- Hot lines or a tank that sit idle for long stretches, such as a guest bathroom or a seasonal home, so water stands and changes before it is used.
Washington-specific notes
In and around Washington, local water reports describe very hard water and iron. Heat speeds up scale in a tank, and iron can add a metallic taste and staining to hot water. Well owners in the Franklin County river-bottom area may find sulfide and iron showing up together, and heat can make either one more obvious. Public reports do not tell you what your own heater is doing, so the simple checks in this guide still matter.
Checks to make before calling anyone
- Confirm the smell appears only on hot water, and note whether it is strongest after the water has sat overnight or during a long idle period.
- Find the heater's age and check the owner's manual for how to reach the anode rod and drain valve. Do not assume it has been checked before.
- On a tank heater, run the drain valve into a bucket for a short time and look at the color and smell. Rust-colored or dark water with a strong odor points toward sediment or a reaction in the tank. Hot water can scald, so take care.
- Run each hot tap for a few minutes after a long idle period, then smell it again. A change after flushing suggests stagnant water was the cause.
- Keep dated notes about when the smell appears, which taps are affected, and what changed, similar to a simple water log.
When to test
A smell that does not clear after flushing, or one that also shows up in the cold tap, is worth a lab test. If your home uses a well, ask the lab about hydrogen sulfide and bacteria testing so you know what is actually present. Until you have results, use your own judgment about drinking and cooking with the hot tap. A smell alone cannot tell you what is in the water, and a certified lab can.