As mentioned earlier in this article, there are a wide variety of contaminants worth removing from tap water. The team here in our lab decided on three primary tests to evaluate the effectiveness of these filters: TDS, pH, and chlorine. Before starting the actual test, each jar was removed from its packaging, cleaned and prepared according to the manufacturer's instructions. This is very important as most of these filters use activated carbon filtration, which deposit sediment in the first few batches of water you filter if not cleaned properly beforehand.
Test for TDS
TDS stands for total dissolved solids and covers many different impurities present in water. Examples of the most common TDS include “calcium, magnesium, sodium, potassium, bicarbonate, sulfate, chloride, nitrate and silica,” according to the US Geological Survey. In practice, calcium and magnesium deposits in tap water result in so-called “hard water”, which has a bad taste and can be actively harmful to health in higher concentrations. (Read more about TDS here It is here.)
We begin TDS testing by mixing an 8-gallon bucket of tap water, measured at 220 ppm TDS, with table salt until we reach a TDS measurement of 300. Generally speaking, 50-150 TDS is considered an ideal range for water. drinkable. We use a Orapxi Water Quality Tester to make these measurements and because the ZeroWater filter also includes a TDS tester, all TDS readings were verified on both devices. Once we established our source control, we measured 1 liter of 300 TDS water into each of the water filter pitchers and allowed the entire amount to pass through the filter.
When finished, we measure the TDS again and observe the percentage change. This process was repeated for higher and lower TDS concentrations, and our findings indicate that each of the units tested is very consistent in removing the same percentage of overall TDS from any water that passes through it.
Chlorine in drinking water may seem strange, but it is actually a very common practice at water treatment plants to add chlorine to the water supply as a disinfectant. This is extremely effective at getting rid of other, nastier contaminants in water, but the World Health Organization estimates that a concentration of ~0.2-4 ppm is standard for tap water, indicating that at least some remains after disinfection.
For our tests, we decided to take things up a notch and test prepared water at a similar concentration to a swimming pool – 10 ppm chlorine. This gave us a clear indication of the changes after filtration. Once again, each filter was tested with 1 liter of solution and compared to the water pre-filtration results, and once again, filters like the ZeroWater substantially outperformed the others.
Testing pH Changes
Finally, during the TDS test, we also measure the change in pH. pH stands for “potential of hydrogen” and is used to quantify the acidity of a substance. A pH of 0 is extremely acidic, 7 is considered neither acidic nor basic, and 14 represents an extremely basic substance. Because the minerals that make up TDS in tap water increase alkalinity, we expected the filtration process to lower the pH of the water. In fact, this was the case, and you can see a table of pH changes below.
Here is a table with the latest results from our TDS removal tests. Data represents an average of three tests for each filter jug.
|TDS (% variation)
|Brita Metro Standard
|Brite every day
|Long Lasting Brita