Water hardness in São João de Meriti
26 mg/L soft
Tap water in São João de Meriti is soft: 26 mg/L (1.5 gpg · 1.5 °dH · 2.6 °fH).
Source: Ministério da Saúde, SISAGUA – controle semestral (Aguas Do Rio 4 Spe Sa), CC BY-ND 3.0 (2026) · data checked 2026-10-20
Range across supply zones: 22–31 mg/L.
São João de Meriti is in the area served by the Guandu treatment plant in Nova Iguaçu, which draws on the Guandu River, itself fed largely by water transferred from the Paraíba do Sul. Records for 2026 give a median of 26.2 mg/L CaCO₃, with individual results from 21.5 to 30.9 mg/L. Scale on kettles and taps is unlikely; soft water also rinses soap slowly, so dose detergent and shampoo sparingly.
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 | 26 mg/L |
|---|---|
| Utility | Aguas Do Rio 4 Spe Sa |
How São João de Meriti compares
- Tap water in São João de Meriti is 38 % softer than the median of the 1915 cities we track in Brazil (43 mg/L).
- By hardness it ranks 1408 of 1915 in Brazil (1 = hardest); 26 % of these cities have softer water.
- In Rio de Janeiro it is number 10 of 44 cities; the regional median is 14 mg/L.
- Nearest city with clearly softer water: Mesquita, 10 km away (14 mg/L).
- Nearest city with clearly harder water: Paraíba do Sul, 69 km away (74 mg/L).
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 São João de Meriti
| 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 São João de Meriti water hard or soft?
It is soft: 26 mg/L as CaCO₃ (1.5 gpg, 1.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in São João de Meriti 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 São João de Meriti water?
1.5 gpg, equal to 1.5 °dH, 2.6 °fH or 26 mg/L calcium carbonate.
What dishwasher salt setting should I use in São João de Meriti?
For 26 mg/L (1.5 °dH) check your manufacturer's table: level 0–1, usually no salt.
Do I need a water softener in São João de Meriti?
No. With soft water a softener adds nothing.
Source
Source: Ministério da Saúde, SISAGUA – controle semestral (Aguas Do Rio 4 Spe Sa), CC BY-ND 3.0 (2026). Method: figure published by the water supplier. Ministério da Saúde, SISAGUA – controle semestral (Aguas Do Rio 4 Spe Sa), CC BY-ND 3.0 · Outdated figure? Tell us