Bottled Water: OCU Reveals Two Best Buys for Quality and Price

Your daily hydration choice may be quietly affecting your health and wallet.

Spain's leading consumer organization, OCU, analyzed over 90 bottled water brands and found two that stand out for quality, composition, and price: La Majuela (sold at DIA) and Aquadeus. The findings challenge the assumption that premium brands are worth the extra cost. Published in June 2026, this comprehensive study evaluates still waters commonly found in Spanish supermarkets, excluding sparkling or flavored varieties. The OCU, known for its scientific rigor, measured parameters such as dry residue, sodium, calcium, magnesium, chlorides, sulfates, and pH, and also conducted a blind taste test to assess flavor. The result is a practical guide for consumers seeking quality without overspending.

The Science Behind the Recommendation

The OCU study focused on three key factors: mineral composition, sodium content, and price per liter. The primary recommendation is to choose waters with weak mineralization, especially for those monitoring sodium intake. High-mineral waters can contain significant sodium, calcium, or magnesium, which may not be ideal for everyone. For example, waters like Vichy Catalán can have over 1,000 mg/L of sodium, while the recommended ones have less than 20 mg/L. The OCU also evaluated dry residue at 180°C, an indicator of total mineral content. Weakly mineralized waters have a dry residue below 500 mg/L, making them suitable for daily consumption and food preparation, particularly for people with hypertension, kidney issues, or those on low-sodium diets.

La Majuela, sourced from a spring in Zaragoza, costs €0.15 per liter and has a dry residue of 210 mg/L and sodium of 8 mg/L. Aquadeus, from Fuente Arquillo in Albacete, costs €0.21 per liter and has a dry residue of 280 mg/L with sodium of 12 mg/L. Both feature weak mineralization and low sodium, making them ideal for daily hydration. In contrast, premium brands like Solán de Cabras (€0.45/L) have a dry residue of 320 mg/L and sodium of 15 mg/L, similar to Aquadeus but at double the price. The OCU highlights that price does not correlate with mineral quality; in fact, some expensive waters have higher sodium content.

“The best water isn't the most expensive: mineral composition and price per liter are the true measures of value.”

Key Findings

• Best value: La Majuela (DIA) at €0.15/L, weak mineralization (dry residue 210 mg/L) and low sodium (8 mg/L). It is the most economical and healthy option in the study.
• Second best: Aquadeus at €0.21/L, balanced composition (dry residue 280 mg/L, sodium 12 mg/L) from Sierra de Alcaraz. Widely available in supermarkets.
• Popular brands overpriced: Font Vella (€0.35/L), Solán de Cabras (€0.45/L), and Bezoya (€0.50/L) often cost more without superior mineral profiles. For instance, Bezoya has a dry residue of 340 mg/L and sodium of 18 mg/L, similar to La Majuela but three times more expensive.
• Tap water remains the most economical and sustainable choice if quality is adequate. The OCU notes that in many Spanish cities, tap water is safe to drink and costs less than €0.002/L.
• Regional variability: The study found significant differences in tap water composition across cities, which may influence the decision to buy bottled water.

Why It Matters for Your Health and Wallet

For health optimizers, water choice impacts sodium intake and hydration quality. High sodium intake is linked to hypertension and fluid retention. The World Health Organization recommends a daily sodium intake below 2,000 mg. If you drink 2 liters of water per day with 100 mg/L of sodium, you would already consume 200 mg from water alone, 10% of the maximum intake. Choosing weakly mineralized waters helps maintain a controlled electrolyte balance and reduces kidney workload.

Financially, the difference adds up. A family consuming 2 liters daily could save over €250 per year by switching from a €0.50/L brand to La Majuela. The OCU calculates that a family of four drinking 3 liters daily (including cooking) could save up to €380 annually by choosing La Majuela over a premium brand. This savings can be redirected to other health aspects, such as fresh food or supplements. It's a rare win-win for health and budget.

Your Protocol for Choosing Bottled Water

1. 1Check the label: Look for "weak mineralization" or "low dry residue" (<500 mg/L) and verify sodium content (ideally <20 mg/L). Avoid waters with sodium >50 mg/L if you have hypertension.
2. 2Compare price per liter: Ignore the total price of the bottle; divide the price by the liters. Larger formats (1.5 L or 5 L) are usually cheaper per liter. For example, a 6-pack of 1.5 L bottles of La Majuela costs about €1.35, i.e., €0.15/L.
3. 3Choose large or reusable containers: Reduces cost per liter and environmental impact. If possible, buy 5 or 8-liter jugs. Also, consider using a reusable stainless steel or glass bottle to avoid single-use plastic.

If you drink bottled water daily, La Majuela and Aquadeus are top picks. If tap water is available, consider a carbon filter if taste or chlorine bothers you. The OCU emphasizes that quality tap water is the most sustainable and economical option, and in many areas it is perfectly safe.

What To Watch Next

The OCU periodically updates its analyses. Future studies may include more store brands and very low-mineral waters, reflecting consumer trends. They might also assess the environmental footprint of plastic vs. glass bottles, as well as the carbon footprint of transporting bottled water. Some brands are starting to offer returnable glass containers, reducing waste.

Functional waters (with added electrolytes or alkaline pH) are gaining popularity. The OCU could evaluate whether they offer real benefits over natural weakly mineralized waters. For example, alkaline waters with pH >8 claim to neutralize acidity, but scientific evidence is limited. Most people get enough electrolytes from diet, so these waters are often unnecessary and more expensive.

The Bottom Line

The OCU makes it clear: you don't need to pay more for quality water. La Majuela and Aquadeus offer balanced composition, low sodium, and unbeatable prices. For most people, tap water remains the best choice, but if you buy bottled, choose wisely. Check labels, compare prices, and prioritize weak mineralization. Your health and wallet will thank you. In a context of inflation and growing environmental awareness, every small saving counts, and water is an excellent starting point.