Most people find out they have a water problem by accident. A showerhead crusts over, towels come out of the wash stiff, or the water heater starts knocking. These signs look alike, but their causes and fixes differ, so spend a few weeks writing down what your water is doing before you call anyone who wants to sell you equipment.
Sort what you notice into three groups
Put each observation into one bucket. The first is appearance: white crust on faucets and showerheads, spots on glassware, or colored stains in sinks and toilet bowls. The second is feel and performance: soap that will not lather, skin or hair that feels dry after a shower, fabrics that look dingy after several washes, or a water heater that runs noisier or heats more slowly than it used to. The third is taste and smell: a chlorine note, a metallic or bitter taste, a rotten-egg odor, or an earthy, musty smell. Each group points toward different causes, and some causes have nothing to do with the water supply itself.
Find out where the problem lives
Check whether the problem shows up at every tap or only one. Note whether it happens on hot water only, cold only, or both. A rotten-egg smell that appears only at the hot tap points at the water heater rather than the supply line. Crust on a single showerhead tells a different story than scale on every fixture in the house. Also record the time of day and whether a washer, dishwasher, or outdoor hose was running at the time. Patterns like these narrow the search far more than a general sense that the water is off.
Check what your utility already reports
If you are on a municipal supply, the utility must publish a water quality report for its customers, usually called a consumer confidence report. You can find it on the utility's website or ask for a printed copy. Look at the table of detected substances and the notes on hardness, pH, and disinfectant levels. The report describes the water as it leaves the treatment plant, not what comes out of your own pipes, because plumbing and the water heater can change the water between the street and your tap. It is still the best starting point you have. If you are on a private well, no utility report exists, and a certified lab test of your own water is where to begin.
Test before you compare
Get a written lab report for your water before you compare treatment companies. Ask the lab for results with units, the detection limits for each test, and the location where the sample was taken. Water that looks clear can still carry hardness, chlorine, or sulfur compounds that a basic home kit may not measure well. When you are ready to weigh companies, you can see how winners are chosen on the award methodology page, which will help you judge whether a shortlist was built on a sound process.
When to stop and call someone right away
Most of what you notice is a quality or equipment issue that can wait a week while you gather information. A few things cannot wait. If the water suddenly turns cloudy, smells of fuel or solvent, or has a sharp chemical odor that was not there before, avoid drinking it and cooking with it until you have reached your utility or your local health department for instructions. If your utility has issued a notice about the supply, follow its directions. If anyone in the home has a health concern connected to the water, bring the lab results to their doctor, since that conversation belongs with them and not with an equipment seller.
Write a one-page summary before you call
Bring a single page to every company you contact. Include what you noticed, which fixtures were affected, whether the problem was hot or cold, the time of day, how long it has gone on, the lab or utility report, and anything you already tried. A company that can work from that page is listening to you. One that asks you to describe the problem from scratch, or wants to skip the water test, has told you something useful too.