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I have a friend, who adamantly believes that water calcification causes a number of problems, including poor health. He also said it made the water taste disgusting. He had recently installed a demagnetiser (or whatever it is - some kind of quack device) which is supposed to filter out the calcium by magnetically attracting it. Ignoring for now the fact that calcium isn't magnetic, of course, and magnets wouldn't have any effect. Let's presume the magic device does actually filter out calcium.

I didn't want to tell him he had been take for a ride (he paid about £200 for the unit), but I did agree to a taste test. I couldn't taste a difference between the uncalcified and calcified water. I've always drunk straight from the tap, with no ill effects so far.

What evidence is there that this water calcification, a) contributes to poor health, and/or b) makes tap water taste bad (apparently.)

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"Ignoring for now the fact that calcium isn't magnetic, of course, and magnets wouldn't have any effect. Let's presume the magic device does actually filter out calcium." haha. Enjoyed that. –  Vian Esterhuizen May 5 '11 at 20:40
My grandmother and grandfather got their water from a spring up a hill. The ground there was limestone, and the water had slowly filtered through, and it was shock full of calcium. It tasted absolutely wonderful, and was the best tasting water of my life, and one of my favorite memories from my childhood is running in after playing in the sun, taking a big ladle that hung by the tap filling it up with cool calcium enriched water and drinking as much as I could. In short: Your friend is absolutely dead wrong on every single point in his claims. –  Lennart Regebro May 5 '11 at 21:42
Can you provide an example of the claim? I've heard of it but a user is flagging this for attention... –  Sklivvz Apr 6 '12 at 2:30
@Sklivvz as per Jeff's answer here please don't decline flags except when they are actually unhelpful. This question clearly lacks a notable claim and since you posted a comment to that effect, the flag should not have been declined. –  Sonny Ordell Apr 6 '12 at 5:44

2 Answers 2

up vote 18 down vote accepted

What makes water hard is calcium carbonate (limescale).

Not only it is not unhealthy, but it is also prescribed as an antacid.

The myth that hard water favours kidney stones has been disproved by a study, which has actually found that the opposite is true: a calcium-carbonate-poor diet increases the risk of kidney stones:

A slightly lower dietary calcium intake (683 versus 711 mg/day, P = 0.04) was noted in case subjects versus control subjects, but interpretation was confounded by the study of prevalent rather than incident cases. Supplemental calcium intake >500 mg/day was inversely associated with stone occurrence.

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A quibble with the first line: Magnesium also makes water hard. –  Oddthinking Oct 16 '11 at 0:09

Summary: Hard water is (slightly) good for you.

If you ignore the effects of limescale on your pipes, boilers, taste (hard water makes worse tea) and any indirect effects these may have on your health there is evidence that hard water leads to slightly lower rates of cardiovascular disease. The result comes from a BMJ paper in 1980 which sought explanatory factors for the different rates of heart disease in different parts of the UK. The paper is here.

The summary conclusion relevant to this question states:

After adjustment for other factors cardiovascular mortality in areas with very soft water, around 0 25 mmol/l (calcium carbonate equivalent 25 mg/l), was estimated to be 10-15% higher than that in areas with medium-hard water, around 1-7 mmol/l (170 mg/l), while any further increase in hardness beyond 1-7 mmol/l did not additionally lower cardiovascular mortality.

So it might be more accurate to say the absence of hardness has a small influence on stroke and heart disease rates. And the effect isn't large, especially when compared to other known influences on these diseases. As the authors say:

...the potential risks from smoking, hypertension, hypercholesterolaemia, and physical inactivity are far greater than the apparent risk from drinking soft water;

Another effect of water hardness that is almost certainly no longer relevant is that hard water prevents the accumulation of lead in water compared to soft water which tends to be acidic and leaches small amounts of lead from lead piping (which was relatively common in some countries until the 1960s). An older BMJ paper from 1973 summarizes this evidence like this:

The present findings suggest that people living in soft water areas have higher concentrations of lead in their bones than those living in hard water areas... the present findings indicate a more generally distributed cause; the ingestion of small doses of lead from drinking water over a long period of time is a possible explanation.

And they further elaborate:

... a concentration of lead which may be harmless in a hard water may not be so in a soft water; in fact, hard water is protective against both the pick-up of lead from pipes and its absorption by the body.

Since lead piping has mostly been eliminated, this effects is no longer likley to have any significance.

So the direct evidence seems to suggest that hard water is (very slightly) good for you.

I have not yet found more recent research results on the topic so it would be interesting to see whether similar studies from other countries or more recent studies show the same effect.

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