If you own a water softener in Lake St. Louis, the simplest way to judge how it performs is to compare water on each side of it. Public water reports describe local tap water as very hard, so the water leaving a working softener should test noticeably softer than the water entering it. Where you collect each sample matters as much as the test you run, so this guide walks through the sampling points and what to do with the results.
Why the sample location matters
A sample is only useful if you know where it came from. Water that sat in a long pipe, passed through a faucet aerator, or came from a hose bib can carry scale, sediment, or stagnant water that has nothing to do with the softener. Label every container with the spot and the date before you leave the sink.
The three common draw points
- Raw supply: a cold tap that connects ahead of the softener. In many homes this is a utility room hose bib or a laundry sink plumbed before the unit. On a private well, it is usually a sampling valve on the line before any treatment.
- Softened cold supply: a kitchen or bathroom cold tap that sits after the softener. This is the main comparison point for daily use.
- Softened hot supply: optional. Use it if you suspect the water heater is holding scale, since heat changes how some minerals behave. Keep it separate from the cold comparison so the results stay clear.
How to collect the sample
- Remove any aerator or screen from the faucet and wipe the outlet with a clean cloth.
- Run the cold water for a few minutes until the temperature settles and the flow sounds steady.
- Fill a clean container, leaving a little air space if the test calls for it, and cap it.
- Repeat the same steps at each point, using the same faucet type and flow rate, so the results line up.
- Test the samples the same day when you can, or keep them cool and out of direct sun until you do.
Bacteria samples need their own handling. Use a container from a certified lab, do not rinse it, and follow the lab instructions for timing. Do not use a home kit bottle for a bacteria test.
What to test on each side
For a softener check, hardness is the main test. A simple hardness kit can show whether the softened cold tap is clearly softer than the raw supply. If both samples read about the same, the softener is not reducing hardness, and the next step is to check how the unit is running before you assume the resin is spent.
Lake St. Louis homes often also notice high pH in the water. A pH test strip on the raw and softened samples will show whether the softener changes that reading. Softening does not always move pH much, so do not expect the numbers to match. The goal is to understand your water, not to chase one perfect result.
If you are on a private well, test the raw sample for the contaminants your area is known for. Iron and manganese can stain fixtures and fouls a softener over time. Nitrates can come from farm runoff or septic systems. Radionuclides occur naturally in the deep aquifers of eastern Missouri, and the former Weldon Spring cleanup site sits within the broader service area, which is a good reason to test a well for radium even though current municipal radium readings are within limits. A raw-side test tells you what the softener is up against, and a softened-side test tells you whether it is changing anything.
Reading the two results together
- Softened side clearly softer: the unit is likely working. Keep watching the salt level and regeneration schedule.
- Softened side nearly the same as raw: check whether the bypass valve is open, whether the brine tank has salt, and whether the unit has regenerated recently.
- Softened side has a new smell, color, or cloudiness: stop using the water for drinking until you have it checked, and note the timing against any recent salt refill or maintenance.
- Results disagree with what you see on fixtures: test again on a different day and note the flow rate and temperature. Water conditions shift with seasons and demand.
Keep a simple log
Write down the date, the sample spot, the result, and the softener status at the time. Include whether the unit had just regenerated, the salt level in the brine tank, and any work done on the system. A short log turns a single confusing result into a pattern you can read over several months.
What to do next
If the comparison shows the softener is not working as expected, start with the basics: confirm the bypass valve position, check the salt, and review the regeneration settings. If those look fine and the results still do not separate, bring your log to a qualified service technician who can inspect the unit. For a private well with any concerning result, a certified lab can confirm what you are dealing with before you choose a treatment path.