Cloudy water from a kitchen faucet can be alarming, especially when you have just changed a filter or added a new system. In many St. Louis homes, though, milky water that clears in a glass is caused by tiny air bubbles that were trapped in the lines, not by anything dissolved or suspended in the water. This guide walks through the simple checks a homeowner can run before deciding whether to call someone.
What cloudiness usually looks like
Air bubbles tend to show up as a white haze that fills a clear glass and then fades from the bottom up as the water sits. Particles behave differently. They may stay suspended, settle into a layer at the bottom, or leave the water looking grainy after it has rested. Watching how the haze behaves in a glass is the first and most useful clue you can gather without any tools.
Checks to run at home
- Fill a clear glass from the cold tap and set it on the counter. Watch whether the haze clears from the bottom up or stays put.
- Run the cold tap for a while, then fill another glass. Cloudiness that clears after a short run often points to air that was trapped in the lines.
- Compare the cold and hot taps. Note whether one side is worse, and whether the difference holds up over several days.
- Check other faucets in the house, including outdoor spigots if you use them for drinking water. If cloudiness appears at several fixtures, the cause may be in the main supply rather than in your under-sink system.
- Write down whether the change started after a filter swap, a plumbing repair, a shutdown, or a water main project in your neighborhood. Timing is often the fastest way to narrow the cause.
Filter and storage questions
Under-sink systems include a storage tank, and a newly installed or recently serviced filter can release air into the lines for a while. The manual for your system should explain how to purge air after a filter change. Follow those steps exactly, and avoid opening fittings or adjusting internal valves unless the manual tells you to. If you are unsure which valve or fitting the manual means, stop and ask a licensed plumber rather than guessing.
Also check the cartridge housings and fittings for loose connections. A slightly loose fitting can introduce air, and it can also leak, so look for drips and damp spots after you run the faucet.
When cloudiness deserves a closer look
Get help sooner if the water stays cloudy after a long run, if the haze does not clear in a glass, if the water has an unusual odor, or if residue remains on dishes or fixtures and does not wipe away. A problem that affects only one fixture and grows worse over time also deserves attention. Do not drink water that looks or smells wrong while you investigate. Use a different source until you know what is happening.
Questions for your water provider
For concerns about the main supply, start with the water provider that serves your address. Ask whether there were recent main repairs, flushing, or other work in your area, and whether any recent testing results are available to you. Providers can share what they have on record, which helps you separate a local plumbing issue from a wider supply issue. In St. Louis, the provider for your specific address may differ depending on where you live, so confirm that first.
Testing if you want more information
A basic home test kit can check some things, such as chlorine or hardness, but no simple kit can identify every substance that might cause a change in appearance. For anything beyond what a glass test shows, a state-certified or accredited laboratory can run a formal analysis and give you a written report. Follow the lab's collection instructions closely, use a clean container, and ask whether they recommend a particular sample type for your concern.
Who to call and what to bring
If your checks point to the filter, storage tank, or fittings under the sink, a licensed plumber can inspect the connections and the system. If the question is about the main supply, call your water provider. Either way, bring a short written record: when the cloudiness started, which fixtures are affected, whether it clears in a glass, and any recent work in your home or on your street. That record makes the conversation faster and helps whoever you call decide what to check next.