Does limescale calcium cause kidney stones?

Myths about limescale in tap water and kidney stones

Does limescale in tap water cause kidney stones? Will hard water cause other health issues?

About 30% of the population in Spain and Italy are concerned about drinking hard calcium rich water. This is also the case for parts of North America. Are they right to be concerned or is it all just a nocebo?

We decided to find out and debunk the myths.

What’s the cause of hard water and limescale?

More than 60% of households in Europe and North America have hard water coming from the tap. This means that it’s more prone to limescale formation but also that it’s mineral rich. 

The source of hard water is typically a river with a lot of sediment which the water picks up along the way to the water treatment plant. But hard water could also come from ground water or a lake. Specifically in the case of limescale this usually means calcium and magnesium which when combined form limescale in tea kettles, coffee machines, glasses, around the faucets and other places.

Water treatment plants generally don’t soften the water due to the following reasons

  1. Would mean removing healthy minerals 
  2. Expensive in terms of energy, material and environmental impact
  3. May impact the water taste negatively

What are the health risks of calcium and limescale?

Calcium is an essential mineral for the body. Our bones need it and actually also our kidneys. The evidence that tap water hardness influences calcium stone formation is weak.

First of all, to avoid kidney stones the best thing you can do is to drink plenty of water (hard or soft). Drinking extra water dilutes the substances in urine that lead to stones. It may help to include some citrus beverages, like lemonade and orange juice. The citrate in these beverages helps block stone formation.


Secondly, most of the large long term studies show no or very little relationship between hard water and kidney stones. For the general population there simply is no increase risk. There are however people with poor health with an increased risk which is why doctors may give a warning.

What does the research on hard water (high on calcium resulting in limescale) conclude about kidney stones?

Hard water does not cause kidney stone, but it may increase the risk of developing kidney stones. Research shows that if you drink hard water after treatment of kidney stones, they increase chances of developing the complication. Your doctor will advise you on the best way to avoid re-occurrence of the kidney stones and the potential health impacts of using hard water. 

But the research shows that it is not the quality of water, rather the quantity of water consumed that matters most in the occurrence of KSD.

However, there is some evidence however that very hard water (mineral rich water) with TDS above 400 ppm could increase risk of kidney stones. In most cases of kidney stones, the blood in a human body, due to certain inherent problems, starts absorbing more calcium from water and food than actually needed. As a result, excess calcium is deposited on the walls of the kidney in the excretion process.

Where do we get calcium from?

We get calcium through dairy products as well as many other foods including beans, almonds, lentils and of course tap water. Eating a diet that’s high in protein, sodium (salt) and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much salt in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.

What are the main causes of kidney stones?

Ironically the number one reason is not drinking enough water and other beverages. Read more about the other causes.

How can you remove limescale from tap water?

Ask a water filter expert and he will come up with a range of expensive solutions to soften the water ranging from salt softeners and ion exchange to 5-stage reverse osmosis filters. Most of the solutions are either an overkill, causes the water to taste bad or are bad for the environment. 

Until recently the most affordable alternative was water carafes using ion exchange raisins. Typically these only reduce limescale by 50% and need to be replaced every month but at least  they somewhat work. 

Thankfully there’s now new innovative technology that is a lot more efficient. Current TAPP 2 reduces limescale for at least 1-2 months and our next generation is a lot more efficient.

Conclusion about the health effect of limescale

In conclusion, the evidence that tap water calcium causes kidney stone formation is weak. However, there is still much we don’t know about tap water so if you want to be on the safe side then check out our limescale filter launching soon.

Read more about Brita vs TAPP, how water filters work and TAPP 2.

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