Is hard water bad for you?
Share
Part of our hard water guide
Your kettle says hard water is a nuisance. The internet says it is bad for you, or good for you. What do the regulators say it does to the person drinking it? You can also check your own tap with a 20-in-1 test strip.
Short answer: The UK regulations set no standard for hardness, and the Drinking Water Inspectorate (DWI) says there are no health-based guidelines for it. The DWI calls 200 to 300 mg/l as calcium carbonate hard. Its cautions concern sodium in softened water and soft water corroding pipework, and hardness differs by area.
By Andrew Tomlinson, WaterKit · Last reviewed 29 October 2026
Is hard water bad for you?
No official source we read says so. The DWI says the Drinking Water Directive and the UK drinking water quality regulations do not specify standards for hardness, calcium or magnesium. The World Health Organization (WHO) background document from 2011 says there are insufficient data to suggest minimum or maximum concentrations, so it proposes no guideline values. The effects the DWI does describe are on kettles, irons, heating elements and lather, and a 20-in-1 test strip gives a hardness reading for your own tap in about a minute.
The regulations set no hardness standard, so a water company meeting the drinking water standards tells you nothing about how hard your own water is. The table covers the health worries people raise, and our hard water guide has the full wording.
| Worry | What the official page says |
|---|---|
| Heart health | WHO. There is some evidence for a protective effect of magnesium or hardness on cardiovascular mortality, but WHO says the evidence is being debated and further studies are being conducted. |
| Eczema (washing, not drinking) | WHO. Exposure to hard water has been suggested to be a risk factor that could exacerbate eczema. WHO says the specific causes of atopic eczema are unknown and that additional studies are under way. |
Is hard water good for you?
The sources we read stop short of saying so, but WHO does put numbers on what drinking water contributes. Its background document says food gives over 80% of the typical daily intake of calcium and magnesium, and water typically 5 to 20%. These are WHO's international figures, not UK ones.
WHO adds that drinking water could be important for people who are marginal for calcium and magnesium intake. The DWI recommends that water companies which artificially soften water keep a minimum total hardness of 150 mg/l as calcium carbonate, citing limited evidence of a link with cardiovascular health. Our limescale guide sets out what each body says on that.
Is hard or soft water better?
The sources we read do not rank them for health. They describe trade-offs, and the cautions sit with soft and softened water. The DWI calls fitting a softener a matter of personal choice. Its bands as calcium carbonate are soft up to 100 mg/l, slightly hard 100 to 150, moderately hard 150 to 200, hard 200 to 300 and very hard above 300.
| Type of water | What the official pages say |
|---|---|
| Hard, 200 mg/l or more | DWI. Hard water causes scaling, which shortens the life of heating elements and makes appliances less efficient, and gives less lather and tide marks. The DWI cites the WHO 2017 guidelines that 200 mg/l or more will produce scale. WHO adds that excessively hard water can also tend to corrode. |
| Soft, 100 mg/l or less | DWI. More corrosive to pipework, which could dissolve plumbing metals such as lead, copper, brass and nickel. WHO says soft water that is not stabilised has a great tendency to cause corrosion, which can be associated with health risks from leachates, and that it scales little. |
| Softened at home by ion exchange | DWI. Calcium and magnesium are replaced with sodium, a softener may risk breaching the sodium standard, and artificially softened water may be aggressive to plumbing. It advises an unsoftened kitchen tap for drinking and cooking. |
Our guide to drinking softened water covers the sodium side, and our lead pipes guide covers the plumbing side.
Can you drink hard water, and does it taste different?
Nothing we read says you cannot. The DWI says water companies must supply wholesome water suitable for drinking, cooking and washing, and that published results show no need for extra treatment at home as a health protection measure.
On taste, the DWI says tap water can vary between regions because of differing hardness and residual chlorine. WHO gives the taste threshold for the calcium ion as 100 to 300 mg/l, depending on the anion, and says higher concentrations are acceptable to consumers. That is for calcium itself, not hardness as calcium carbonate, so it does not line up with the DWI bands.
What about babies and low-salt diets?
The DWI's caution is about softened water. It says too much sodium can be a problem for premature babies, whose kidneys are not good at filtering it out of the blood, and for people on a low-sodium diet. It also says artificially softened water should not be used to make up baby feeds.
Why might my tap not match the area figure?
Because the area figure is an average. Your tap may differ, and the DWI gives several reasons. Hardness depends on local geology, and the DWI says its map shows only typical hardness, with local variation in some areas that the map does not show. WHO names limestone and chalk as the usual sources of calcium and magnesium. A figure for the area does not tell you what comes out of your own tap.
Your home adds its own differences. If you have a softener, the DWI advises keeping the kitchen tap unsoftened, so taps in one house can read differently. Scale builds up in hot water systems, heating elements, kettles and irons, and the DWI says temporary hardness is the part that boiling removes, forming scale. Running a strip at each tap shows whether yours differ, and our how hard is my water guide and postcode guide cover how to find your supplier's figure.
“The area figure is only a typical value, so I would never assume it describes the water at your own kitchen tap, especially if you have a softener fitted. Running a strip at each tap takes a minute and shows you where your home actually sits.”
How can I check my own tap with a test strip?
Fill a clean glass or cup with tap water, dip one strip, wait 30 to 60 seconds and match the hardness pad to the chart, or enter the colours in the results portal. The pad steps are 0, 25, 50, 100, 250 and 425 mg/L. The portal does not say whether they are read as calcium carbonate, the unit of the DWI bands, so this reading against the bands is our own. The free checker needs no app or account, and the QR code on your chart opens it.
- 250 or 425. These sit in the DWI's hard band (200 to 300) or very hard band (over 300). Between 100 and 250 the pad has no step.
- 100 or below. This sits within the DWI's soft band (up to 100). There is no UK hardness standard, so no reading is a pass or a fail.
- Kitchen tap against a softened tap. If you have a softener, test both. The unsoftened tap should read higher.
The pad gives one total hardness band. It does not split calcium from magnesium, and it cannot show sodium or the state of your pipework. The strip cannot read lead at the UK limit, so our lead pipes guide is the place to start on that. A strip result is not a legal sample, and your water company's figure remains the reference for your area. The optional bacteria test is a separate presence screen, read after 24 to 48 hours.
The area figure is an average, and the DWI says its map shows only typical hardness, with local variation in some areas, so your own tap may sit in a different band. The hardness pad is the one that matters here. A reading in a different band from your area figure, or a higher reading at an unsoftened tap than at a softened one, points to a difference at that tap, and testing again after any change shows whether it has moved. Best pack: 20 strips, enough to test your kitchen tap, a second tap and the hot tap, and again after any change, £5.99 (or £10.99 with a bacteria test), with free 2nd Class delivery on every order. See the kit
Your hard water questions
Is hard water bad for you?
No official source we read says so. The DWI says the UK regulations specify no standard for hardness, and WHO proposes no guideline value.
Is hard water safe to drink?
The DWI says there are no health-based guidelines for water hardness, and that published results show no need for extra treatment at home as a health protection measure. We make no safety claim of our own.
Is drinking hard water bad for you?
In the DWI and WHO pages we read, we found no statement that it is. The cautions in the official pages concern sodium in softened water and corrosion by soft water.
Is hard water good for you?
The sources stop short of saying so. WHO says water typically gives 5 to 20% of calcium and magnesium intake, and that the cardiovascular evidence is debated.
Is hard or soft water better for you?
No official source we read ranks them. The DWI and WHO describe scale with hard water, and corrosion of pipework with soft water.
Is hard or soft water better?
It depends on what you weigh. Hard water scales heating elements and gives less lather. The DWI says soft water at 100 mg/l or less is more corrosive to pipework, and home softening adds sodium.
Can you drink hard water?
Nothing we read says you cannot. The DWI says water companies must supply wholesome water suitable for drinking, and the UK regulations include no hardness standard.
Is soft water better than hard water?
The official pages do not say so. They list benefits of softer water for scale and lather, and cautions about corrosion and, where softened at home, sodium.
How does water hardness affect water quality?
The DWI says it affects scale, lather and tide marks, plus a scum on hot drinks, and that taste can vary between regions. It says soft water at 100 mg/l or less is more corrosive to pipework.
Sources
- Drinking Water Inspectorate, Water Hardness / Hard Water (undated page; no standards for hardness, calcium or magnesium; bands; WHO 2017 figures of 200 and 100 mg/l; 150 mg/l when softening; softener advice and sodium; scaling, lather and scum; temporary hardness; map and local variation; read 29 October 2026) and Domestic water filters and softeners (undated page; wholesome water; no health-based guidelines for hardness; hardness and taste; softeners and sodium; baby feeds; corrosion of plumbing metals; read 29 October 2026).
- World Health Organization, Hardness and Chemical fact sheets: Hardness (undated pages; hardness in the Guidelines for drinking-water quality, fourth edition with addenda to June 2026; read 29 October 2026), and Hardness in Drinking-water, background document, 2011 (food share and 5 to 20% water share; sources; taste threshold; corrosion and scaling; softened water; eczema; cardiovascular evidence; no guideline values; read 29 October 2026).
- Drinking Water Inspectorate, Drinking Water 2025, compliance with water quality standards (overall compliance 99.97% in England, 24 water companies, 59.74 million consumers).
- WaterKit, Water Test Kit (20-in-1 strip, 30 to 60 second read, optional rapid coliform test read after 24 to 48 hours, from £3.99, free 2nd Class delivery on every order) and results portal (hardness pad steps 0, 25, 50, 100, 250 and 425 mg/L; read 29 October 2026). The reading of the pad steps against the DWI bands is WaterKit's own.
Contains public sector information licensed under the Open Government Licence v3.0.