I’ve spent more than ten years working in residential plumbing and water treatment, and TDS is one of the numbers homeowners latch onto the fastest—often after reading quick explanations or test results shared on sites like https://www.waterwizards.ai/blog. Someone buys a meter, dips it into a glass of water, sees a number pop up, and suddenly that number becomes the entire story. In my experience, TDS is useful—but only in context. On its own, it leaves out more than most people realize.
I’ve had homeowners panic over a TDS reading that looked “high,” while completely ignoring the iron staining their sinks or the chlorine smell in their showers. I’ve also seen people brag about ultra-low TDS water that still tasted terrible.
What TDS actually measures
TDS stands for Total Dissolved Solids. It’s a measure of everything dissolved in water that can carry an electrical charge—minerals, salts, metals, and other inorganic material. A TDS meter doesn’t identify what those substances are. It only reports a combined number.
That distinction matters. A reading of 300 could be mostly calcium and magnesium, or it could include sodium, iron, or other dissolved material. The meter doesn’t tell you which.
I once tested two homes with nearly identical TDS readings. One had clear, good-tasting water that only caused scale. The other had noticeable staining and odor issues. Same number, completely different experience.
Why low TDS doesn’t automatically mean “better”
People often assume lower is always better. Reverse osmosis systems reinforce that idea because they dramatically reduce TDS. For certain uses—drinking water, cooking, taste—that can be a benefit.
But low TDS doesn’t guarantee good water. It doesn’t account for bacteria, chlorine, organic compounds, or how water behaves in plumbing. I’ve seen low-TDS water that still smelled off because the issue wasn’t dissolved solids at all.
Taste is another factor. Some people love very low-mineral water. Others find it flat. That preference has nothing to do with safety and everything to do with personal taste.
Why higher TDS isn’t automatically bad
I’ve also seen homeowners worry about moderately high TDS readings even though their water caused no practical problems. Minerals like calcium and magnesium raise TDS, but they’re not harmful. In fact, they’re the reason hard water leaves scale.
Hardness issues are mechanical, not health-related. High TDS from hardness affects appliances and fixtures, not whether the water is drinkable.
What TDS completely misses
TDS doesn’t measure chlorine, chloramine, bacteria, sulfur odors, or sediment. It doesn’t tell you whether water will stain laundry, smell in the shower, or taste strange once heated.
I’ve tested water with low TDS that destroyed water heaters because of corrosive chemistry. I’ve also tested high-TDS well water that worked fine once iron and sulfur were treated. The number alone didn’t predict the outcome.
How TDS is actually useful
In my work, TDS is best used as a comparison tool. It’s helpful for seeing changes—before and after filtration, or between raw water and treated water. It’s also useful for monitoring RO system performance over time.
What it isn’t good for is diagnosing problems by itself. I’ve never solved a water issue by chasing TDS alone.
Common mistakes homeowners make with TDS
The biggest mistake is treating TDS like a grade. People want a pass or fail number. Water doesn’t work that way. Another mistake is buying equipment based solely on TDS reduction without understanding what needs to be removed.
I’ve also seen people ignore obvious symptoms because their TDS reading “looked fine.” Spots, smells, pressure loss, and taste issues don’t disappear just because a meter says everything’s okay.
Looking at the full picture
After years of testing water in real homes, I’ve learned that numbers are tools, not answers. TDS tells you something, but never everything. The most reliable approach is combining measurements with observation—how the water tastes, smells, behaves, and affects the home.
When people stop treating TDS like a verdict and start seeing it as one data point among many, decisions get easier. The water makes more sense, and the solutions tend to fit better.
That’s usually when frustration drops—and the meter goes back in the drawer where it belongs.