If your home in Lake St. Louis is served by the municipal water system, the yearly water quality report is the most useful single page you have. Water suppliers publish these reports for their customers, and the results come from testing done across the year. The trouble is that the report is written in shorthand. This guide explains the terms you are most likely to see, so you can read the report yourself and decide what to do next.
Homes on private wells do not receive this report. If you draw water from a well, the testing you need is your own, and that is covered near the end.
Terms That Show Up Again and Again
Hardness
Hardness describes the calcium and magnesium dissolved in water. Public reports for the Lake St. Louis area describe the tap water as very hard. In daily life, hardness shows up as scale on fixtures, soap that struggles to lather, and spots on glassware. It is mainly a question of how the water behaves in your home.
pH
pH measures how acidic or basic water is. Local reports note that pH is high. A high pH can affect how water interacts with pipes and fixtures, so it is worth keeping in mind when you look at staining, scale, or buildup around the house.
Disinfection Byproducts: TTHMs and HAA5
When a water supplier disinfects water, the disinfectant can react with natural organic matter in the source water and form byproducts. Two groups are commonly reported. Total trihalomethanes, called TTHMs, and haloacetic acids, called HAA5, are each compared against a limit set for the public supply. Because these byproducts form as water travels through the distribution system, results can vary by location and season, which is why the report often lists them as averages over a period of time.
Chlorine Disinfection
Reports also state the disinfection method. Lake St. Louis reports list chlorine disinfection, which keeps water free of microorganisms as it moves through the pipes. The report tracks the disinfectant levels within the system, and those levels are part of how the supplier shows that treatment is working.
Not Detected and Running Averages
A result marked as not detected means the test did not find the substance at a level the lab can measure. Some byproduct results are reported as a running average rather than a single sample. When you see an average, look for the period it covers, since a single high sample can look different from a yearly average.
Reading the Report Step by Step
- Find the table of detected substances and check the units and the limit listed beside each one.
- Look at the year range the results cover so you know how current the data is.
- Note which results are averages and which are individual samples.
- Check for any notice about a violation or corrective action. If there is none, the report is saying the supplier did not flag one that year.
- Compare what the report says with what you actually notice at home, such as scale, stains, or odor.
Questions to Bring to Your Supplier
If something in the report is unclear, the supplier is the right place to ask. These questions tend to give you the most useful answers:
- Where in the system are byproduct samples taken, and how often?
- Has the disinfection method changed, or is a change expected?
- Where can I find the full sampling data behind the summary table?
When Your Home Is on a Private Well
Private wells in the area around Lake St. Louis can have concerns that differ from municipal water. Issues mentioned locally include iron and manganese staining from river-bottom wells, a rotten-egg smell from deeper bedrock wells, nitrates from agricultural runoff and septic systems, coliform bacteria and E. coli, and naturally occurring radium and other radionuclides in the deep eastern Missouri bedrock aquifers. The former Weldon Spring cleanup site sits inside the service area, which is a real reason to test a private well, even though current municipal radium readings are within limits. Testing is the only way to know what your own well contains.
Keep Your Own Record
Read your report once a year and keep a copy with your home papers. Alongside it, write down anything you notice in the house, such as stains, scale, odd smells, or changes after plumbing work. If the report and your observations do not match, a home test kit or a certified lab can help narrow down the question. Keeping both in one place makes the next decision easier.