We all know water is essential—but how much do you really need to stay healthy and alert? Should tea and coffee count? Is bottled water better than tap? What about chlorine, fluoride, or filtering?
This guide answers the most common hydration questions with clear, science-backed advice.
The NHS recommends 6 to 8 glasses of fluid per day—that’s around 1.5 to 2 litres. But this doesn’t have to be just water. Tea, coffee, milk, and even food all contribute to your daily hydration needs.
Still, plain water remains the healthiest option: it’s calorie-free, sugar-free, and gentle on your teeth and digestion.
“Water, lower-fat milk and sugar-free drinks including tea and coffee all count. But water is a good choice.” - NHS Eatwell Guide.
Yes—absolutely.
Although tea and coffee contain caffeine, they are still hydrating in moderate amounts. According to the European Food Safety Authority (EFSA), up to 400mg of caffeine per day (about 4–5 cups of coffee or 6–8 cups of tea) does not cause dehydration [2].
So your morning brew is helping you stay hydrated—not drying you out.
Not in the UK. Our tap water is among the safest in the world. The Drinking Water Inspectorate reports that over 99.96% of UK tap water meets or exceeds safety standards [3].
So why choose bottled water?
Taste
Convenience
Perceived purity
However, bottled water has its own concerns—particularly around plastic.
Drinking bottled water occasionally is fine, but regular use raises two issues:
1. Microplastics
A 2019 WHO study found that over 90% of bottled water samples contained microplastic particles, mostly from packaging and processing [4].
However, the WHO concluded there is currently no evidence that microplastics in drinking water pose an immediate health risk at current levels.
“Based on the limited information available, microplastics in drinking water do not appear to pose a health risk at current levels. But we urgently need to know more.” — Dr Maria Neira, WHO Director, Public Health [4]
2. Environmental Impact
Bottled water has a high carbon footprint and generates plastic waste.
In the UK, only around 45% of plastic bottles are recycled [5].
✅ Verdict: Tap or filtered water is just as safe, cheaper, and far better for the planet.
In the UK, your tap water may be:
Hard – higher in calcium and magnesium (e.g. London, South East)
Soft – lower in minerals (e.g. parts of Scotland and Wales)
Benefits of Hard Water:
Adds calcium and magnesium to your diet
Some studies suggest it may help protect against heart disease, although the evidence is mixed [6]
Downsides:
Limescale build-up in kettles, taps and boilers
Can irritate sensitive skin
Some dislike the taste
From a hydration point of view, both hard and soft water are equally effective.
Yes. In the UK, chlorine is added to kill bacteria and viruses, making water safe to drink.
Typical chlorine levels are 0.1–0.5 mg/L, well below the WHO’s safe limit of 5 mg/L [7].
You might notice a mild chlorine taste or smell—this can be reduced by letting water stand, or using a filter.
✅ Chlorine helps make UK tap water among the safest in the world.
Some UK areas add fluoride to water to reduce tooth decay (e.g. Birmingham, Newcastle, parts of Cumbria).
Fluoride is added at 1 mg/L, a level considered safe and effective by public health bodies.
According to the NHS: “There is no evidence that water fluoridation causes harm to health and plenty of evidence that it helps reduce tooth decay.” [8]
If you’re unsure whether your water is fluoridated, check your supplier’s water report or use the UK Government fluoridation map here: https://www.gov.uk/government/publications/water-fluoridation-health-monitoring-report-for-england-2022
Filtered Water
Using a jug filter (e.g. Brita) can improve the taste and quality of tap water. It helps by:
Reducing chlorine, microplastics, and limescale
Retaining beneficial minerals
This makes filtered tap water a cost-effective and low-waste choice for daily drinking.
Distilled Water
Distilled water is purified by boiling and recondensing, removing nearly all minerals and contaminants.
It’s safe in the short term—but it contains no calcium, magnesium, or sodium.
If your diet includes plenty of vegetables, nuts, seeds, whole grains, and dairy (or fortified plant alternatives), you'll be getting the key minerals—like calcium and magnesium—that distilled water lacks, making it unlikely to pose any nutritional risk.
However, if distilled water is your only source of water and your diet is poor, you may develop mild mineral deficiencies over time—particularly in magnesium, which is already low in many modern diets.
The World Health Organisation warns that long-term use of low-mineral water (distilled, reverse osmosis, etc.) could affect electrolyte balance and increase risk in certain groups [9].
Even mild dehydration (just 1–2%) can affect the body:
Brain - Fatigue, poor focus, low mood, headaches [10]
Digestion - Constipation, slow bowel movements
Kidneys - Impaired function, higher risk of UTIs or stones [11]
Skin - Dry, dull appearance
Urine - Dark yellow or amber colour
Chronic low-level dehydration can affect mental clarity, bowel regularity, and energy levels, particularly in older adults [12].
As a simple guide:
✅ Pale, straw-coloured urine
❌ Dark yellow or amber urine
✅ Regular, soft bowel movements
❌ Dry mouth or tiredness without cause
✅ You rarely feel thirsty
Start your morning with a glass of water
Keep a reusable bottle with you
Add lemon, mint, or cucumber for flavour
Eat hydrating foods – cucumbers, oranges, soups, tomatoes
Drink more when it’s hot, humid, or when you're exercising or unwell
Don't wait to feel thirsty—sip regularly throughout the day
Yes—but it’s rare. Hyponatraemia occurs when excessive water dilutes the sodium in your blood. It’s mostly seen in:
Endurance athletes over-drinking plain water
People with certain medical conditions
For most people, drinking to thirst and checking urine colour is the best approach.
1. Does tea or coffee dehydrate you?
No. In moderate amounts, they are hydrating and count towards your fluid intake [2].
2. Is bottled water better than tap water?
Not in the UK. Tap water is regulated, safe, and often more thoroughly tested [3].
3. Is hard water good or bad for you?
It's safe—and can be a source of calcium and magnesium. Taste and limescale are the main issues [6].
4.Can I drink distilled water every day?
Only if your diet provides the minerals it lacks. Long-term exclusive use isn’t ideal [9].
5. How can I improve the taste of tap water?
Use a filter jug, or add natural flavourings like lemon, mint, or cucumber.
This article is for general information only and is not intended to treat or diagnose medical conditions. If in doubt please check with your GP first.
References:
NHS. (2023). Eatwell Guide – Hydration.
EFSA. (2015). Scientific Opinion on Caffeine. EFSA Journal.
Drinking Water Inspectorate. (2024). Advice for Consumers.
WHO. (2019). Microplastics in Drinking Water.
Recycle Now. (2023). Plastic Bottle Recycling.
Yang, C.Y. (1998). Calcium, Magnesium, and Cardiovascular Disease Mortality. J Toxicol Environ Health A.
Drinking Water Inspectorate. (2022). Chlorine in Drinking Water.
NHS. (2023). Fluoride – Benefits and Safety.
WHO. (2004). Nutrients in Drinking Water.
Benton, D. & Young, H. A. (2015). Do Small Differences in Hydration Status Affect Mood and Cognitive Function? Nutr Rev.
NHS. (2022). Kidney Disease Symptoms.
NHS. (2023). Hydration and Confusion in Older People.
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