If your St. Louis tap water suddenly smells like a swimming pool, the first thing to know is that chlorine is a common disinfectant in municipal water, and its smell is most noticeable when the level changes. A change does not always mean something is wrong, but it is worth working through a short checklist before you decide what to do next.

Start with the pattern

Before you test anything, write down what you notice. Chlorine smell can be strong at one time and gone at another, and the pattern tells you a lot.

  • Is the smell in cold water, hot water, or both?
  • Does it appear in every tap, or only one?
  • Did it start after street work, a water main repair, or a seasonal change in the system?
  • Does it fade after you run the tap for a while?

A smell that shows up in every tap and started after work on nearby lines often fades as the system settles. A smell in just one fixture points toward plumbing inside your home.

Check the filters and containers

Carbon filters remove chlorine, so a filter that is worn out, or one that has been in use too long, can start to smell or stop doing its job. Pitcher filters, refrigerator filters, and under-sink cartridges all need replacing on schedule. Also check the water in any pitcher or bottle that has sat in the refrigerator. Water left in a closed container can take on odors from the container itself. Rinse the pitcher and try fresh water straight from the tap.

Compare hot and cold

If the smell is only in hot water, the cause is probably in the water heater or the hot side of the plumbing rather than the supply. A rotten egg or sulfur smell is different from chlorine and points to a different cause, often bacteria in a water heater or a problem with the anode rod. Treat that as a separate question. Chlorine smell is sharp and pool-like and usually shows up in both hot and cold water.

Test the chlorine level at home

A simple test tells you whether chlorine is present and about how much. Free chlorine test strips and simple drop kits are sold at hardware and pool supply stores around St. Louis. Follow the instructions on the package, let the cold tap run for a bit, and test water from the kitchen tap and from the fixture where the smell is strongest. Compare the result against the scale on the package. Keep notes of the date and the result so you can compare later.

A reading that looks the same in every tap and fades over a few days fits the pattern of a temporary change. A reading that stays high in one fixture, or a smell that lingers across many days, is worth raising with your water provider.

When to contact your water provider

Call your water provider if the smell is strong across the whole house, lasts more than a few days, or comes with discolored water, new sediment, or a noticeable change in pressure. Describe what you saw, when it started, and which taps are affected. Ask whether there was recent work on the lines near your home and whether any notices went out to customers. Your notes from the checklist will make that call faster and clearer.

When to bring in a professional

If the smell stays in one fixture after you have ruled out the filter and the water heater, the cause may be in the home plumbing. A licensed plumber can look at the fixture, the supply lines, and the water heater and explain what they find. Ask for a clear explanation of the cause before agreeing to any repair.

What chlorine is and is not

Chlorine is added to treated water to control microbes as the water travels through pipes. The smell tells you that a disinfectant is present, but it does not tell you everything about your water. Testing for chlorine measures one substance. A broader water test is a separate step, and it is the right tool when you have questions about what else might be in your water.