Do you have hard water in your home?  Hard water comes with a whole range of side effects, including spots on your dishes, potential mineral build up in your pipes and around your tub,as well as drying out your hair and skin.  Plus, some just don’t like the taste or the sometimes cloudy appearance.  

So what do you do when you’re looking for a solution to water hardness?  One of the most common and effective means of softening your water is to invest in a water softener filtration system.  But in order to be sure you get the right one for your home, you need to know the level of relative hardness.  That is, do you have slightly hard water, very hard, or somewhere in between?

In this article, we briefly explain water hardness, the measurement scale most commonly used to measure mineral water hardness, and how you can go about measuring the hardness of your water.

What Is Water Hardness?

Hard water is water that has a high mineral content, especially calcium and magnesium.  The water picks up mineral content as it flows through deposits of chalk, limestone and gypsum.  

If you get your water from a private source like a well on your property, this can often yield hard water.  Intuitively, this makes sense – a well involves drilling into an aquifer to access groundwater.  And groundwater can be permeated across all sorts of rocks and sediment.  

However, your municipality, region or city can also supply hard water, depending on the source.  In the U.S., hard water is especially common across the southwest and midwest, although it is certainly not limited to those areas.  

In the U.S. and Canada, hard water is safe for drinking, cooking and cleaning.  However, as mentioned above, it can lead to costly problems like film or residue buildup on sinks, dishes, tubs and water using appliances.  Linens and clothes can also be affected by being washed in hard water, and may wear and lose their color more quickly.  

Moreover, lime scale can build up on pipes and appliances that use hard water (e.g. a water heater).  This can prove costly and frustrating for home owners and industrial water users as well.  

The common solution is to invest in a water softener, which is a machine that filters out the mineral ions (calcium and magnesium) from the water and replaces them with salt ions.  However, in order to purchase a water softener with the correct capacity, you first need to know how ‘hard’ your water is, in relative terms.  This means you need to measure the hardness of your water.

Measuring The Hardness of Water

Water Hardness Scales

Water hardness is typically measured in one of three units.  Thankfully, we can easily translate the units of one scale to another without too much trouble.  

The first two scales used are essentially interchangeable.  They measure the hardness of water in either milligrams per litre (mg/L) or parts per million (ppm).  Generally, any dissolved calcium or magnesium content from 60-120 mg/L (or ppm) is thought of as moderately hard, 121-180 mg/L as hard, and over 180 mg/L as very hard.  On the low end of the scale, 17-60 mg/L is considered only slightly hard, and anything less than 17 mg/L is considered soft.

The third scale used is a measure of grains hardness per gallon of water, or grains per gallon (gpg).  The more grains of dissolved minerals in water, the harder the water.  Most water falls somewhere between 1 (soft) and 10 (hard).  As a reference, here is a simple table that shows how to convert between the 3 water hardness measurement scales.

Grains per Gallon mg/L or ppm Water Hardness
Less than 1 Less than 17 Soft
1-3.5 17.1060 A Little Hard
3.5-7 60-120 Moderately Hard
7-10 120-180 Hard
Over 10 Over 180 Very Hard

Testing Water Hardness

Simple Home Soap Test

An easy do it yourself method for measuring water hardness is the soap test.  While this method is not the most precise or reliable, it can supply you with a rough estimate as to your level of hard water.  

You’ll need some dish soap, a glass or plastic bottle (of at least 16 ounces or so), and a measuring cup or glass.  Fill the bottle with 12 ounces of water, add 10 small drops of liquid dish soap, close the cap and shake vigorously for a few seconds to mix the soap and water.  You’re looking to see if soap suds have formed at the top of the bottle.  If they have, then you have relatively soft water.

However, if it requires many more drops of soap to make visible suds, you have some degree of hard water.  The more soap required, the harder the water.  Typically, about 30 drops of soap will be required for water that has about 60-120 mg/L of hardness, and 40 drops for 120-180 mg/L.  

Test Kits

For a more accurate reading, invest in a hard water test strip set. Test strips have small amounts of chemicals on them that react to the minerals in hard water. Some manufacturers make different strips for testing drinking water and aquariums, so make sure you buy the right type for your purpose.

To use a test strip, simply dip the designated end into a glass or bowl of water and hold it there for about a second, until the end changes color. You shouldn’t have to hold it in the water for long, so pull it out once you have your reading.

You can also take a few test strips to different parts of your home, to see if water hardness varies in one part of your house or another.

Once you have completed the test, compare the color on the tested strip to the legend or explanatory scale that came with the kit to get a precise estimate of your water hardness. Simply match the color on the end of the strip to the closest color on the given scale. Usually, a darker color means harder water.

As an alternative to test strips, test kits with tablets are another way to test water hardness. The tablets are made up of a chemical compound that will react to change the color of the water, based on the hardness. For most tests, this involves partially filling a small receptacle (to about 10 ml of water), adding the tablet to the water, sealing the receptacle and shaking for a few seconds.

Usually, a red color indicates a hardness level of 20 mg/L or above, while a green-ish color means a lower hardness level, but consult the instructions and legend on the test kit for an exact reading.

Checking With Your Water Provider

A further, very simple method to estimating your water hardness is to just ask your water supplier or local government. Often, they keep fairly current measures of water hardness and can provide them to you at no charge.

Of course, the measure they have might not mirror the exact hardness level coming out of your faucet. And this will not always be an option, especially for those who use a private or semi-private water source.

Read: Do I Really Need a Water Filter?