Should you be concerned that hard water will cause kidney stones? What is hard water anyway? Through this article, you will understand whether there is a link between hard water and kidney stones or not, how to know whether the water in your house is hard water or not, and what the solutions are.
What is hard water?
Hard water is the water which has a relatively high amount of calcium and magnesium. Hard water also has minerals like aluminum, iron, zinc, manganese and barium, but most of the “hardness” comes from calcium. The degree of hard water is measured in “grains per gallon”. All of these minerals come in our water from soil or rocks.
Hard water is known for making less “lather” when mixed with soap. It can also leave a ring around your bathtub or white residue on appliances like coffee makers or ice machines. Hard water often has a different taste compared to soft water, may leave a residue after you wash your hair, make cleaners less effective and makes water heaters less energy-efficient.
Other than these annoyances, hard water is not bad for your health. In fact, some studies have linked hard water with lower risk of mortality from heart disease. However, no conclusions can be made from these preliminary studies.
But what about kidney stones? Does hard water cause kidney stones? Let’s first understand how much calcium is in hard water and whether that calcium amount could increase the risk of kidney stones.
How much calcium is in hard water?
The amount of calcium in hard water varies widely depending on location and water source.
The World Health Organization defines hard water based on the amount of calcium carbonate per liter.
- Moderately hard water: contains 60-120 milligrams of calcium per liter
- Hard water: contains 120-180 milligrams of calcium per liter
- Very hard water: contains more than 180 milligrams of calcium per liter
How much magnesium is in hard water?
Comparing to calcium, there is not much magnesium in hard water. Different water sources have different amounts of calcium, but usually hard water has around 50mg of magnesium per liter.
Does our body absorb minerals from hard water?
On average, our body absorbs around 50% of the minerals in drinking water. Surprisingly, minerals from water contribute 5%-20% of the total amount of minerals we eat!
The amount of calcium absorbed from hard water is very different between people. Intestinal absorption of calcium is highly dependent on how much calcium your body needs. For example, if your body needs more calcium, it will absorb a greater percentage of calcium from your food. Other factors, such as vitamin D status, also impact calcium absorption.
What is soft water?
On the flip side, soft water is defined as having a low amount of calcium per liter. The World Health Organization defines soft water as having less than 60mg of calcium per liter.
Where do you find hard water?
Hard water is found all over the world. Water hardness is dependent on the level of minerals in the soil where you live.
Does hard water cause kidney stones?
People who have not had kidney stones before
Hard water is unlikely to cause kidney stones for most people.
A few small studies have shown that urine calcium goes up after drinking hard water. And high urine calcium is a risk factor for kidney stones. However, these studies have not found more kidney stones in people who live in areas with hard water.
If you have not had kidney stones before, hard water is unlikely to cause kidney stones.
People who have had kidney stones before
If you have had kidney stones before, or have high urine calcium, you should measure to know how much calcium is in your tap water. Drinking a lot of hard water could make the problem of high urine calcium worse.
Calcium supplements are associated with kidney stones, whereas eating high calcium foods is protective. Although no research has been done, calcium carbonate in hard water probably acts more like calcium supplements than calcium from food.
Calcium amount in hard water might be a especially concerning issue for people who are recommended to drink a lot of water to prevent kidney stone. People with kidney stones are often told to drink at least 2.5 liters of fluid per day. At these high intakes, hard water can add a little bit more of calcium to your body.
Please note that very little research has been done to determine whether hard water causes kidney stones in people who have had kidney stones. Therefore, it is hard to say whether hard water is a big contributor to kidney stones. However, it’s better to know the calcium amount in your water. Knowledge is power!
How do I know whether my water is hard water or not?
Test strips
You can check the hardness of your water at home with some simple test strips. These test strips will tell you approximately how much calcium is in your water.
You can also try a home water test kit, which will give you much more information about your water. This test kit will tell you the specific amount of calcium, sodium and other minerals in your water.
Check with your water supplier
If your water comes from a factory in your city, annual testing is required and the results must be made available to the public. From the test result, you can see how much sodium is in your water too. Call your water supplier or search online for your water test report.
Make sure your supplier reports the amount of calcium in your water – not all suppliers do!
Non-specific test at home
You can also do an simple test at home to check calcium and sodium levels in your tap water. Of course, this option doesn’t tell you exactly how much calcium is in your water, but it is a free and easy way to see whether you need to examine your water further.
What can I do if my water is hard water?
If you have hard water, in most cases, this is not a problem, and the hard water will not impact your health.
However, if you have kidney stones and are concerned about the extra calcium amount, there are a few options for you.
Note that Brita filters (or similar brands) do not remove calcium or sodium from water.
Buy bottled water or distilled water
Distilling water removes all minerals, including calcium and sodium. Distilled water has zero calcium or sodium.
Instead of buying individual water bottles, a more environmentally friendly option is buying gallons of distilled water. Or you can even purchase large jugs of distilled water and a water dispenser for your home.
Use a water softener
In areas that have very hard water, the city or municipality often softens water for you.
If you have well water, you should have a water softener at home.
Sodium & water softeners
Water softening removes some of the calcium and magnesium from hard water. Water softening usually involves swapping each molecule of calcium or magnesium for a molecule of sodium. The harder your water is, the more calcium and magnesium must be removed, and the more sodium is added during softening process.
This method could be a problem for people with kidney stones. A high sodium diet can cause kidney stones. Usually, the amount of sodium added during water softening is minimal, but it can be significant in some cases.
How much sodium is added during process of softening water?
The amount of sodium that is added during water softening varies widely. For very hard water, about 150mg of sodium is added per quart. Assuming you drink 3 liters of tap water per day, this is an additional 450mg of sodium (20%-30% of the daily recommended amount). For softening less hard water, less sodium is required.
Your city’s water quality report may tell you how much sodium is in your water. Sodium is usually reported in “parts per million”, which is equivalent to “mg per liter”. You can usually find water quality reports online, or you can call your city.
You can also test your water for sodium yourself with a home test kit.
How can I prevent kidney stones?
In many cases, hard water is not the sole cause of kidney stones. Hard water may exacerbate high urine calcium, but is unlikely to be the initial cause.
There are many causes of kidney stones, and a poor diet is one of them.
Generally, the key parts of a healthy diet for kidney stone prevention are:
- Drinking lots of water
- Limiting sodium
- Limiting added sugar
- Eating a right amount of protein
- Eating lots of fruits and vegetables
