Hardness, nitrates, pH, sanitary compliance: the real tap water quality in Rennes (moderately hard water), with official Hub'Eau data updated monthly.
✓ Compliant with sanitary standardsWater in Rennes measures 15.5°f — moderately hard. This is the typical profile for many French municipalities: some visible scale, regular maintenance but no essential water treatment. A softener isn't justified at this level unless scale deposits become particularly bothersome or plumbing dates from before 1990. Official sanitary tests declare it compliant with current standards across all monitored parameters.
Results from the latest official sanitary samples (Hub’Eau, French Ministry of Health). Click a card to understand what each parameter measures.
Sanitary compliance summarises adherence to French regulatory limits across all analysed parameters (bacteriology, chemistry, radioactivity). Compliant water can be consumed directly from the tap without additional treatment.
The TH (titre hydrotimétrique) measures calcium and magnesium concentration, expressed in French degrees (°f). The higher it is, the harder the water and the faster limescale deposits on surfaces and in appliances.
Nitrates come mainly from agriculture and waste water. The French regulatory limit is 50 mg/L; below 25 mg/L, the level is considered low.
PFAS are persistent chemical compounds, sometimes called "forever chemicals", used in industry. The vigilance threshold used here is 0.1 µg/L, consistent with current health recommendations.
pH measures water acidity. Regulations require a value between 6.5 and 9: outside this range, water may encourage pipe corrosion or affect taste.
Free chlorine is added to disinfect water and prevent bacterial growth in the distribution network. High levels can produce a perceptible taste or odour, without health risk at authorised levels.
Turbidity measures water clarity, in NTU (nephelometric turbidity units). A low value indicates clear water with few suspended particles.
Conductivity reflects overall water mineralisation, in µS/cm. It has no strict sanitary threshold but indicates the dissolved mineral salt content.
Maintenance budget: ~£43/year
For 2 persons, water at 15.5°f deposits around 0.7 kg of limescale per year in your appliances. Estimated cost in descalers, salt and filters.
Calcium: ~25 mg per litre
Your water provides 25 mg of calcium/L, which is 3% of the recommended daily intake.
Filter jug: cartridge every 8 months
At 15.5°f, replace the cartridge every 8 months. An under-sink filter lasts 6 to 12 months.
Drinking water in Rennes, in the Ille-et-Vilaine department is managed by spl ebr, which handles production, treatment and distribution of tap water in the municipality. The last available official sanitary analysis for Rennes dates from 24 June 2026.
Compare the water quality in Rennes with any other city available on the site.
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How does Rennes compare to the 113 cities in the Ille-et-Vilaine department and the 4806 largest cities in France in our database, on key water quality indicators.
Comparison based on 113 cities in Ille-et-Vilaine department and the 4806 largest cities in France in our database.
Top 10 cities in the Ille-et-Vilaine department ranked by tap water quality in our database.
Rennes ranks 5th out of 113 cities in the department in our database.
Tap water in Rennes has a quality index of 6.7/10 (good quality) in our database, calculated on nitrates, PFAS, pH, free chlorine and turbidity. This is a comparative reading of Hub'Eau data, not an official rating.
Tap water hardness in Rennes is 15.5°f (French degrees), making it moderately hard water. The average is 16.9°f in the Ille-et-Vilaine department and 22.1°f across our entire database.
Moderately. At 15.5°f, water in Rennes is moderately hard: limescale traces appear over time on surfaces that aren't wiped down, but not a daily problem with regular maintenance.
Not necessarily. At 15.5°f, regular antiscale maintenance is often sufficient; a softener is worth considering mainly if deposits become bothersome daily.
Yes. In the last available official sanitary analysis (24 June 2026), water distributed in Rennes was declared compliant, meaning it can be drunk directly from the tap. Official conclusion: "Eau d'alimentation conforme aux exigences de qualité en vigueur pour l'ensemble des paramètres mesurés." This is a point-in-time sample, not real-time monitoring.
The pH measured in Rennes is 8.1. Regulations require a value between 6.5 and 9: the water is within this range.
Compare tap water quality in other cities of the Ille-et-Vilaine department, ranked by quality index.
Methodology: the quality index compares each city against the 4806 other cities in our database on 5 parameters (nitrates, PFAS, pH, free chlorine, turbidity) and averages its relative position on each. This is not an official rating, only a simplified comparative reading of Hub’Eau data.