Understanding Total Dissolved Solids
Total Dissolved Solids (TDS) refers to the concentration of inorganic and organic substances dissolved in water. This includes minerals like calcium and magnesium, salts, and certain metals. While a moderate level of TDS is normal and often considered healthy for drinking water, there are specific instances where pure, mineral-free water is required. Common applications include:
- Aquariums: To create a specific water chemistry for sensitive aquatic life.
- Steam Irons and Humidifiers: To prevent mineral scale buildup that can cause damage over time.
- Car Detailing: For a spot-free rinse that prevents mineral deposits from drying on surfaces.
- Laboratories and Specialty Brewing: To ensure precise results without mineral interference.
Method 1: DIY Distillation on Your Stovetop
Distillation is a centuries-old process that effectively removes almost all contaminants, including TDS, by mimicking the natural rain cycle.
What You'll Need:
- Large stainless steel pot with a lid
- Small, heat-safe glass bowl
- Wire baking rack (optional, to elevate the bowl)
- Ice
- Stovetop
Step-by-Step Process:
- Fill the large pot about halfway with tap water.
- Place the baking rack inside the pot. If the glass bowl is tall enough to float without touching the bottom, the rack is not necessary. The key is to keep the collection bowl above the boiling water.
- Place the small, empty glass bowl on the rack or floating in the water.
- Turn the pot's lid upside-down and place it on the pot. This creates a dome shape that will collect condensation.
- Place ice cubes on top of the inverted lid. This will cool the surface, causing the steam to condense more quickly.
- Bring the water in the large pot to a low, steady boil. The steam will rise, hit the cold lid, and condense into purified water, which will drip into the glass bowl.
- Continue boiling until you have collected enough distilled water, making sure the pot does not boil dry.
- Turn off the heat, let everything cool down, and carefully remove the bowl of distilled water.
Method 2: Reverse Osmosis (RO) with a Deionization (DI) Stage
For a more automated and efficient solution, a reverse osmosis system with an added deionization stage is the gold standard for achieving true 0 TDS water.
The Two-Step Purification Process:
- Reverse Osmosis (RO): The water is forced through a series of pre-filters (sediment and carbon) and then through a semipermeable RO membrane. This membrane has microscopic pores that effectively remove up to 99% of dissolved solids, salts, and other contaminants.
- Deionization (DI): After the RO membrane, the water is passed through a separate DI cartridge filled with ion exchange resins. These resins attract and remove any remaining charged particles (ions), bringing the TDS level down to zero. This is the crucial step that perfects the water from an RO system, which typically leaves a few ppm of residual TDS.
Considerations for an RO+DI system:
- Cost: Initial investment is higher than for distillation, but it is more convenient and less energy-intensive for regular use.
- Efficiency: RO systems produce some wastewater, but newer models are more efficient.
- Maintenance: Requires periodic replacement of filters and DI cartridges.
Method 3: Standalone Deionization (DI) Systems
While often used in conjunction with RO, standalone DI filters can also be effective for smaller, batch-based needs. Pitcher-style filters are a common example, like those using DI resin beds.
How it works:
- Tap water is poured into the pitcher.
- The water passes through the DI resin bed, where the ion exchange process occurs, removing dissolved solids.
- The filtered, low-TDS water collects in the pitcher below.
Best for:
- Small quantities of water.
- Occasional use, like topping off a humidifier.
Limitations:
- Cartridges have a limited lifespan, especially with high-TDS source water.
- Not suitable for high-volume, continuous use.
How to Test Your Water's TDS
Regardless of the method you choose, it's important to verify your results with a TDS meter.
Using a TDS Meter:
- Purchase an inexpensive, handheld TDS meter online or at a home improvement store.
- Turn on the device.
- Dip the metal probes of the meter into a small cup of your purified water.
- Read the parts per million (ppm) displayed on the screen. True 0 TDS will read as 0 ppm.
- Repeat the process with your tap water to see the baseline TDS level.
Comparison of Methods
| Feature | Distillation (DIY) | RO with DI Stage | DI Cartridge (Pitcher) |
|---|---|---|---|
| Effectiveness | Highly effective, but requires careful execution | Highly effective, most reliable for true 0 TDS | Effective for small batches, can reach near-zero |
| Initial Cost | Low (uses existing kitchen items) | High (requires system purchase and installation) | Low to medium (pitcher and cartridge) |
| Operating Cost | High (energy consumption) | Moderate (filter replacements, some wastewater) | Moderate to high (frequent cartridge replacements) |
| Speed | Slow, batch-based process | Fast for consistent supply | Slow, batch-based process |
| Convenience | Low (requires active monitoring) | High (automated, on-demand) | High (easy to use, no installation) |
| Best For | Occasional, small-batch needs | Consistent, high-purity demands | Small volumes, occasional topping off |
Considerations for Health
While creating water with 0 TDS is useful for certain tasks, it is important to remember that this process also removes beneficial minerals like calcium and magnesium. For general drinking purposes, the World Health Organization (WHO) and EPA both have recommended TDS ranges that allow for these important minerals. Unless specifically required, you may not need or want truly 0 TDS water for daily consumption.
- Learn more about water quality guidelines and standards from the official sources, such as the EPA Drinking Water Standards.
Conclusion
Achieving 0 TDS water at home is a manageable goal with a few different approaches. Distillation offers a cheap, hands-on method for small quantities, while an RO+DI system provides a reliable, high-volume solution for serious water purification needs. For quick, small-batch purification, DI filter pitchers are a convenient alternative. The right choice for you will depend on the intended use and your budget, but in every case, a TDS meter is the final, crucial tool for confirming the success of your efforts.
