If your St. Louis home smells like rotten eggs when you run the hot tap, you are not alone in wondering what is going on. The smell is usually from sulfur compounds in the water, and the first job is figuring out where it starts. A few simple checks at home will narrow the problem down before you spend time or money on repairs or testing.
What the smell usually means
Hydrogen sulfide is a gas that gives water its rotten egg odor. Some water carries it naturally, especially well water. Other times it forms inside a water heater, where certain bacteria can react with sulfate in the water and with the metal anode rod inside the tank. The result is the same at the tap, so you need to test to find the source.
Municipal supplies in St. Louis are treated and monitored, so a smell that shows up only on the hot side points more often to the water heater than to the supply itself. A smell on both hot and cold taps points toward the water source or the main plumbing.
Start with a side-by-side smell test
Do this before changing anything, and do it in a well ventilated room.
- Run the cold tap in the kitchen for about a minute, then smell the water from a clean glass. Do not taste it.
- Run the hot tap in the same sink for the same time, then smell that water in a clean glass.
- Repeat both steps at a bathroom sink and a tub or shower, since a smell can be stronger in one area.
- Note which taps smell, how strong the smell is, and whether it changes after the water runs for a while.
- Check whether a sewer-type smell comes from a floor drain or a dry trap. That smell is different and usually comes from the drain, not the water.
Read the results
- Smell only on hot water: Start with the water heater. Sulfur smell from the heater is common, and a qualified plumber can check the tank and the anode rod.
- Smell on hot and cold water: Look at the water source. Ask your water provider whether recent work or a service change could explain it, and consider a lab test.
- Smell that comes and goes: Pay attention to timing. A smell after long periods of non-use, such as a vacation, often points to stagnant water in the heater or pipes.
- Smell only at one fixture: Check that fixture first. A clogged drain, a dirty aerator, or a trap that has dried out can all cause odor at a single sink.
When to get the water tested
A home test kit can show some basic conditions, but a sulfur smell calls for a lab test if the source is unclear. Ask the lab to test for hydrogen sulfide and for bacteria, since both can be part of the picture. A lab report will give you measured levels and a clear answer that you can compare over time. Keep the report with your household records so you can see whether anything changes after a repair.
If you are on a private well near St. Louis, testing is more important. Well water can carry sulfide from the ground, and the well itself may need a closer look. Testing at the source, not just at one tap, will help you decide what to do next.
Safety while you sort it out
- Do not drink or cook with water that has a strong or unusual smell until you know the cause.
- Open a window or run a fan in the room where the smell is strongest.
- If the smell is very strong, or if you notice a gas odor near the water heater, leave the area and contact the right professional or emergency service right away.
- Do not work on a gas water heater or its controls unless you are trained to do so.
- Write down what you tested, when you tested it, and what you saw, so the next person who looks at the problem has a clear starting point.
Most rotten egg smells come down to one of two places, the water heater or the water source. A careful side-by-side test at home will point you toward the right one, and a lab test will confirm it when the answer is not obvious.