If the cold water in your Arnold home smells like rotten eggs, the first job is to find out where the smell starts. A sulfur odor in cold water usually comes from the well, the pressure tank, or the plumbing that carries water through the house. Each source calls for a different check, so it helps to narrow things down before you buy any treatment.

What causes the smell

Hydrogen sulfide is a gas that gives water a rotten egg smell. It can be dissolved in groundwater from the start, or it can form when bacteria in a well, a pressure tank, or a dead-end pipe act on sulfate, a dissolved mineral common in groundwater. Sulfate itself has no smell, so you cannot judge it by taste or odor. Because the two often appear together, a lab test that covers both gives a clearer picture than a guess based on smell.

Homes on public water in Arnold are less likely to have a source problem, since the supply is treated and tested under regular reporting. Even so, a sulfur smell can still come from hot water heaters, drains, or long stagnant lines, so the house plumbing is worth checking.

Narrow down the location

Run the cold tap closest to where the water enters the house, then run a tap at the far end of the home. Note whether the smell is strong at one fixture, all over the house, or only at certain times of day. Write down what you find.

  • Smell at every cold tap, strongest near the entry point: the well, pressure tank, or supply line is the more likely source.
  • Smell only at one tap or one bathroom: look at that fixture, its supply line, and any drain traps nearby.
  • Smell only when hot water runs: the water heater is the likely source, and that is a separate check from the cold supply.
  • Smell after a long absence from home: stagnant water in the lines or tank may be the cause, and running taps for a few minutes may clear it.

Check the well and pressure tank

If your home runs on a private well, look at the well cap and vent for cracks, insects, or debris. Check the pressure tank for signs of rust or standing water around the base. A tank that has not been drained in a long time can hold bacteria and sediment, and a cleaning schedule from a qualified service provider is a reasonable step. Keep any service records, since they help a lab or technician understand the system's history.

Test before you filter

A lab test is the way to confirm what is in the water. Ask for hydrogen sulfide, sulfate, iron, manganese, and total coliform and E. coli testing at a minimum. Use a certified lab and follow its sampling instructions exactly, including the bottle type, the draw order, and how fast the sample must reach the lab. Sample at the kitchen cold tap that is used for drinking, and record the date and time on the form.

Private well owners in the south or west parts of the area should also add lead to the test list. EPA has been working on lead and other heavy metals in private wells tied to the Southwest Jefferson County Mining Superfund area, so sampling for lead is a sensible step there, even if the smell is the only concern you have noticed.

Reading the results

Once results arrive, compare each measured item with the guidance from the lab and the agency that covers your water source. Sulfide results point toward a treatment choice that is different from one for sulfate or bacteria. A result showing coliform or E. coli is a separate issue and calls for a prompt response, such as shock disinfection of the well and retesting, before any other treatment is planned.

Deciding what to do next

Once you know the cause, you can make a plan. A smell that comes from the water heater may only need the heater flushed and the anode checked. A sulfur smell from the well may call for oxidation or a targeted filter, and the choice depends on the lab numbers and your household's use. Keep the test results in a folder with the date of each sample, and retest after any change so you can see whether the smell and readings have actually improved.