How scores work
The Waterphile Score is a number from 0 to 10. It shows how close a water's published mineral values are to ideal ranges taken from public guidance. It is our editorial score, not a health or safety rating. Every water on this site is legally sold drinking water.
What we look at
We score 9 properties, using the numbers each brand publishes on its own label, website or water report:
pH · total dissolved solids (TDS) · sodium · calcium · magnesium · sulfate · chloride · nitrate · bicarbonate
Where the ideal ranges come from
For each property we collect the values set by public bodies and average them into one ideal range. We use only sources we have checked ourselves:
- WHO Guidelines for drinking-water quality (2022): taste and acceptability levels, and the nitrate guideline value.
- WHO, Nutrients in drinking water (2005): suggested ranges for calcium, magnesium, TDS and bicarbonate.
- US EPA secondary standards and US FDA bottled water rules: taste and appearance levels.
- EU mineral water rules (2009/54/EC) and the EU drinking water directive (2020/2184): the low-sodium label and pH limits.
- German mineral water rules: the "suitable for infant food" label criteria for sodium, nitrate and sulfate.
How distance lowers the score
- Inside the ideal range, a property scores close to full marks. Where there is an optimum point (for calcium, about 50 mg/L) or a clear middle of the range, the very centre gets full marks, and the edges of the range get 90%.
- Outside the range, points fall the further away the value is, measured in proportion: going from 20 to 40 costs the same as going from 200 to 400. A property reaches zero at a "too far" level that also comes from the sources, such as the WHO taste threshold of 200 mg/L for sodium.
- Low minerals cost less. WHO's current guidelines set no minimum for minerals, so a very light water loses at most half the points for TDS, calcium, magnesium and bicarbonate.
- Health limit: nitrate above 50 mg/L (the WHO guideline value) scores zero for nitrate.
Weights
pH, TDS, sodium, sulfate, chloride and nitrate count fully. Calcium, magnesium and bicarbonate count half, because their ranges rest on older or less firm sources.
Missing data, ranges and age
- Missing values: we score only what the brand publishes, and take 0.1 off for each of the 9 properties it leaves out. The score always shows how many it covers, for example "8/9".
- Not enough data: we need at least 5 of the 9, including sodium and either pH or TDS. Otherwise we show "Not enough data".
- Ranges: some brands publish a range because they bottle from several springs. We score the worst value in the range and mark it "varies by source".
- Age: we take 0.3 off if the analysis is more than 3 years old, and 0.1 off if the brand gives no date.
What the score is not
The score doesn't say whether a water is safe, healthy or right for you, and it says nothing about taste preferences. It only measures distance from published guidance, using the brand's own numbers. If you have a health question, ask your doctor.
Ideal ranges and sources
Tap for a short explanation of each property.
| Property | Ideal | Scores zero | Weight | Sources |
|---|---|---|---|---|
| pH | 6.5–8.5 best at 7.5 | below 4.5 and above 9.5 | 1 | WHO 2022, EPA 2026, EU DWD 2020 |
| TDS | 225–500 mg/L best at 335 | below 100 mg/L (min. half points) and above 1000 mg/L | 1 | WHO 2005 2005, WHO 2022, EPA 2026, FDA 2026 |
| Sodium | up to 20 mg/L | above 200 mg/L | 1 | EU 2009, DE 2026, WHO 2022, EU DWD 2020 |
| Calcium | 36.7–80 mg/L best at 50 | below 26.7 mg/L (min. half points) and above 200 mg/L | 0.5 | WHO 2005 2005, WHO 2022 |
| Magnesium | 16.7–30 mg/L best at 22.4 | below 10 mg/L (min. half points) and above 60 mg/L | 0.5 | WHO 2005 2005 |
| Sulfate | up to 248 mg/L | above 500 mg/L | 1 | WHO 2022, EPA 2026, FDA 2026, EU DWD 2020, DE 2026 |
| Chloride | up to 250 mg/L | above 500 mg/L | 1 | WHO 2022, EPA 2026, FDA 2026, EU DWD 2020 |
| Nitrate (as NO3) | up to 10 mg/L | above 50 mg/L | 1 | DE 2026, WHO 2022, EU DWD 2020 |
| Bicarbonate | 30–396.6 mg/L | below 15 mg/L (min. half points) and above 793.2 mg/L | 0.5 | WHO 2005 2005 |
Example: Evian
Each property gets a mark from 0 to 1. We take the weighted average, multiply by 10, then subtract any data deductions.
| Property | Published | Ideal | Mark (0–1) | Weight |
|---|---|---|---|---|
| pH | 7.2 | 6.5–8.5 | 0.991 | 1 |
| TDS | 345 mg/L | 225–500 mg/L | 0.999 | 1 |
| Sodium | 6.5 mg/L | up to 20 mg/L | 1.000 | 1 |
| Calcium | 80 mg/L | 36.7–80 mg/L | 0.900 | 0.5 |
| Magnesium | 26 mg/L | 16.7–30 mg/L | 0.974 | 0.5 |
| Sulfate | 14 mg/L | up to 248 mg/L | 1.000 | 1 |
| Chloride | 10 mg/L | up to 250 mg/L | 1.000 | 1 |
| Nitrate | 3.8 mg/L | up to 10 mg/L | 1.000 | 1 |
| Bicarbonate | 360 mg/L | 30–396.6 mg/L | 1.000 | 0.5 |
| Weighted average × 10 | 9.90 | |||
| Missing values (9/9 published) | −0 | |||
| Analysis date not published | −0.1 | |||
| Waterphile Score | 9.8 | |||
Total weight used: 7.5. Calcium at 80 mg/L sits on the edge of its ideal range, so it gets 0.9, not 1. pH 7.2 is just off the 7.5 centre.
All scores
Scores computed from the published values on each brand page. Full rules: version 0.2-draft.