Water, Hydration, and Limescale: What Changes When You Start Drinking Water in Ireland

A recurring complaint in consultations is a sharp decline in water intake after moving to Ireland. The phrasing is usually the same: "in Brazil I used to drink water, here I can't".

It is not a matter of behavioural change or lack of discipline. It is a change in the organoleptic characteristics of the water — and the response to this change is predictable. This article describes what actually changes, what does not pose a health risk, how much water is reasonable to consume, and what each type of filter removes.

In Summary

• The mains water supply in Ireland is treated, monitored, and safe for consumption.

• What reduces intake is the residual taste of chlorine, not water hardness.

• The white deposit in kettles and appliances is calcium and magnesium carbonate: it is an equipment problem, not a health one.

• Hard water contributes, in a modest way, to calcium and magnesium intake.

• Activated carbon filters act on taste and odour; only ion-exchange resin reduces hardness. They are distinct technologies.

The Picture Seen in Consultations

The complaint is rarely presented as a lack of water. It arrives via other symptoms: a slump in performance mid-afternoon, headaches at the end of the day, changes in bowel habits after moving country, or persistent dry skin during the winter.

When investigating fluid intake, the pattern that emerges is consistent — a significant reduction compared to what was habitual in Brazil, almost always accompanied by the observation that the water "won't go down".

What Actually Changed: Chlorine and Hardness

Two distinct factors are often confused, and the distinction between them is the central point of this article.

Chlorine: The Factor That Alters Taste

Chlorination is the standard method for disinfecting the water supply and ensures microbiological safety throughout the entire distribution network. Residual chlorine is, therefore, an indicator that the system is working as it should.

The side effect is sensory: a perceptible taste and odour, often described as similar to swimming pool water. For those coming from mineral water, bottled water, or domestic filters — with a neutral sensory profile — the difference is immediate.

This point deserves emphasis because it is often dismissed as fussiness: sensory acceptability is a real determinant of fluid intake. Water with an unpleasant taste is consumed in smaller quantities, and the consequence of this — mild and chronic dehydration — is what actually constitutes a clinical problem.

Hardness: The Factor That Is Not a Health Problem

Water in much of Ireland travels through limestone formations before reaching the supply network, which increases the concentration of calcium and magnesium salts. This is what is known as hard water.

The manifestations are well-known: white deposits in kettles, limescale in washing machines, marks on bathroom surfaces, and fabrics feeling harsher after washing.

It is important to be precise about the nature of this deposit. It consists of calcium and magnesium carbonate — minerals, not contaminants. The damage is to property, affecting appliances, not health.

Furthermore, hardness is not uniform across the country: it varies significantly depending on the supply zone. Checking Uisce Éireann by Eircode provides information on the condition of a specific residential area.

The Nutritional Contribution of Hard Water

There is one aspect that is rarely considered and which flips the usual reading of the problem.

The calcium and magnesium dissolved in drinking water have bioavailability comparable to food sources, and the World Health Organization recognises the contribution of drinking water to the intake of these minerals. The magnitude of this contribution is modest and depends on local hardness — but it is not zero.

The practical implication is relevant for a specific profile: those with low dairy consumption — due to intolerance, dietary choice, or replacement with plant-based drinks — find in hard water an additional source of calcium that often goes unnoticed. In this context, removing the hardness from drinking water represents the suppression of a source, rather than a gain.

How Much Water Is Reasonable to Drink

The "eight glasses a day" recommendation has no identifiable physiological basis and does not account for body weight, activity levels, or environmental conditions.

There are two more defensible ways to estimate individual needs.

Population Reference Values. The European Food Safety Authority (EFSA) establishes an adequate intake of total water — including that from food — at approximately 2.0 litres per day for adult women and 2.5 litres per day for adult men, under moderate temperature and physical activity conditions.

Estimate Proportional to Weight. In clinical practice, the reference of approximately 35 mL per kilogram of body weight is often operationally useful, as it is easy to calculate and scales with body size. For 60 kg, the result is around 2 litres daily.

Both values are starting points, not rigid goals. The need increases with exercise, high ambient temperatures, and — a factor frequently underestimated in Ireland — prolonged periods in environments with central heating on, a condition that reduces relative humidity and increases insensible water loss throughout the winter.

Do Tea and Coffee Count?

They do. The diuretic effect of caffeine in habitual consumers is modest and does not negate the fluid intake from the drink, contrary to what is often claimed.

The caveat lies elsewhere and concerns composition: when daily intake is concentrated in several mugs of tea with milk and sugar, the discussion shifts from hydration to energy intake and added sugars.

Filters: What Each Technology Actually Removes

This section exists because confusion between the two types of filters is widespread — and understandable, given that the same brand markets both.

• Activated Carbon — found in bottles with integrated filters (e.g., MicroDisc). Removes chlorine, odours, and particles. Does not reduce hardness.

• Ion-Exchange Resin with Carbon — found in filter jugs (e.g., Maxtra+ cartridges). Removes chlorine, odours, carbonate hardness, and some metals. Reduces hardness.

The distinction is stated by the manufacturer itself. BRITA describes the carbon filter as a system that retains elements that compromise taste, such as chlorine, while allowing minerals like calcium and magnesium to pass through. The line of cartridges specifically designed for hardness even includes this function in the product's commercial name.

The practical consequence is straightforward:

• If the goal is to start drinking water again, the factor to correct is the taste — and a carbon filter solves this, with the advantage of preserving calcium and magnesium.

• If the goal is to protect appliances, the recommended technology is ion exchange.

Two additional clarifications regarding filter jugs: they do not remove existing limescale — deposits in a kettle are dissolved with an acidic solution, such as vinegar, not through filtration — and the ion-exchange capacity of the resin becomes exhausted. An expired cartridge continues to act on taste but stops reducing hardness, a scenario in which the presumed protection is no longer occurring.

A Note on Filter Marketing

Some advertising material in the sector links domestic filtration to the removal of hormone residues and pesticides. This association is not justified in the Irish context: the water supply is treated, monitored, and subject to regulatory control.

The legitimate argument for using a domestic filter is taste — and that is sufficient, because it is what determines whether the water will actually be consumed.

Final Considerations

The summary is short: Irish water is safe; limescale deposits do not pose a health risk and have their own mineral contribution; and the factor that reduces intake is the residual taste of chlorine — a limitation with a simple and low-cost solution.

When late-afternoon fatigue persists after correcting water intake, the investigation should follow other paths, discussed in another article on this site.

References

The references below are listed by source and topic. Direct consultation is recommended for further depth.

• Calcium and Magnesium in Drinking Water: World Health Organization — document on the public health significance of calcium and magnesium in water for human consumption.

• Water Intake Reference Values: EFSA — scientific opinion on dietary reference values for water (adequate intake of total water, including food).

• Caffeine and Fluid Balance: literature on the modest diuretic effect of caffeine in habitual consumers, without compromising the drink's fluid contribution.

• Water Hardness by Supply Zone: Uisce Éireann — Eircode search.

• Filtration Technologies: BRITA technical documentation on activated carbon filters (MicroDisc) and ion-exchange resin cartridges (Maxtra+), including the hardness reduction range.

Consultations

I am a Brazilian nutritionist providing consultations for Brazilians living in Ireland. The follow-up considers the local context — the supermarkets where you shop, the weather conditions, and the work routines of those living here.

Book a consultation to structure your nutrition based on the routine you have today.