Using a TDS Meter to Measure Water Quality
If you've had a few issues with how your water tastes, it's perhaps because there's too much of a certain kind of mineral or nitrate impacting the water quality. The principal constituents found in water are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogen carbonate, chloride, sulfate, and nitrate anions.
We understand if you need to go and google exactly what a few of those things are!
But the short of it is that if you have too many dissolved in your water, it will taste bad—and worse, harm your health.
According to the World Health Organisation, unhealthy water can be carcinogenic, contribute to coronary disease, and increase mortality rates when TDS levels are too high.
So we understand why you might be in the market for a TDS tester.
And here's one of the best:
While you can use a water test kit to check for common contaminants, a Total Dissolved Solids meter (TDS) helps you measure the concentration of those dissolved substances.
This is essential when evaluating how well your water filtration system is performing, such as a reverse osmosis filter.
A TDS meter is simple to use, and most give real-time readings within seconds.
They're a crucial tool if you're treating your water at home, especially if you're concerned about heavy metals, mineral buildup, or general taste issues.
TDS meters estimate the amount of dissolved solids by measuring the electrical conductivity of the sample.
The principle is straightforward: the more ions present, the more conductive the water.
The result is shown in parts per million (PPM). A reading of 1 ppm means 1 milligram of dissolved solids per kilogram of water.
So, What Then Is a Good or Bad TDS Reading?
The World Health Organization offers this guideline:- TDS level less than 300 mg/liter: Excellent
- 300–600 mg/liter: Good
- 600–900 mg/liter: Fair
- 900–1200 mg/liter: Poor
- More than 1200 mg/liter: Unacceptable
Write down your baseline so you can evaluate whether your system is working effectively.
TDS meters are useful for aquarium owners too. High TDS levels can stress fish and promote algae blooms.
Fish Tanks and Measuring TDS
TDS meters are useful for aquarium owners too. High TDS levels can stress fish and promote algae blooms. You want to keep water within a healthy range, especially in freshwater setups.
TDS meters can help you track when to top up or do partial water changes.
For freshwater tanks, aim for 130–195 ppm unless you're keeping a species with specific needs.
How to Calibrate a Digital TDS Meter
Like with a pH meter used in brewing, calibration ensures accuracy. Most meters come factory-calibrated, but over time, they can drift due to residue buildup or sensor wear. Use a known calibration solution to check the meter’s accuracy and follow the manual’s instructions closely. Here's a video guide on using calibration solutions properly:
Does a TDS Meter Need Automatic Temperature Control (ATC)?
Yes—if accuracy matters. ATC compensates for how temperature affects water’s electrical conductivity. Without it, readings could be misleading, especially if you're testing warm tap water or water straight from a filtration system. If you're investing in a meter, look for:- ATC capability
- Clear LCD or LED display
- Calibration function or included solution
- Waterproof probe or casing (for durability)
- Measurement range at least up to 9999 ppm
Final Thought: What to Look For When Buying a TDS Meter
Not all TDS meters are created equal. If you're buying one, especially online, consider:- Accuracy tolerance (±2% or better is ideal)
- Battery life and auto-off function
- Ease of use: single-button operation is a plus
- Trusted brand or strong user reviews
- If it measures additional parameters (like temp or EC)