Water hardness in Teresina
20 mg/L soft
Tap water in Teresina is soft: 20 mg/L (1.1 gpg · 1.1 °dH · 2 °fH).
Source: Ministério da Saúde, SISAGUA – controle semestral (Aguas De Teresina), CC BY-ND 3.0 (2025) · data checked 2026-10-20
Range across supply zones: 18–24 mg/L.
Teresina's two main treatment plants, ETA-Norte and ETA-Sul, both draw from the Parnaíba River, with deep wells as a complement. Records for 2025 give a median of 19.6 mg/L CaCO₃, with individual results from 17.6 to 23.5 mg/L. Water this soft rarely forms visible scale, so a softener is not needed and detergent can be dosed lightly.
Portaria GM/MS nº 888/2021 sets a maximum of 300 mg/L CaCO₃ for total hardness (dureza total); operators report it in mg/L to SISAGUA.
Water data
| Total hardness | 20 mg/L |
|---|---|
| Utility | Aguas De Teresina |
How Teresina compares
- Tap water in Teresina is 54 % softer than the median of the 1915 cities we track in Brazil (43 mg/L).
- By hardness it ranks 1581 of 1915 in Brazil (1 = hardest); 17 % of these cities have softer water.
Ranking of the hardest and softest water in Brazil →
What it means at home
- Little or no limescale in kettles, water heaters or washing machines.
- Soap lathers easily; water does not dry skin or hair.
- Dishwasher: salt setting at minimum or off.
- No softener needed; a jug filter only changes taste.
How much salt will you use for softening?
No. Water this soft does not need softening.
Descale a coffee machine or kettle about every 6 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Teresina
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 1 °dH |
| AEG / Electrolux | 1 |
| Beko | 1st |
| Hoover | S0 |
| LG | H0 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Teresina water hard or soft?
It is soft: 20 mg/L as CaCO₃ (1.1 gpg, 1.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Teresina safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Portaria GM/MS nº 888/2021 sets a maximum of 300 mg/L CaCO₃ for total hardness (dureza total); operators report it in mg/L to SISAGUA.
How many grains per gallon is Teresina water?
1.1 gpg, equal to 1.1 °dH, 2 °fH or 20 mg/L calcium carbonate.
What dishwasher salt setting should I use in Teresina?
For 20 mg/L (1.1 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in Teresina?
No. With soft water a softener adds nothing.
Source
Source: Ministério da Saúde, SISAGUA – controle semestral (Aguas De Teresina), CC BY-ND 3.0 (2025). Method: figure published by the water supplier. Ministério da Saúde, SISAGUA – controle semestral (Aguas De Teresina), CC BY-ND 3.0 · Outdated figure? Tell us