How to test water hardness & how to measure it using test strips, a water hardness soap test solution and other methods.

This article explains how to measure water hardness or grains of hardness: a measure of water mineral content. We provide a table of water hardness measurements and we discuss different methods for measuring water hardness including a simple soap test.

Electronic instruments can also measure water hardness but are a cost that most homeowners can eschew given the very low, even free costs of other water hardness test methods.

We give references on where to buy water low-cost but quite effective water hardness tests and we describe how various water hardness test kits are used and how to choose among them.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

How to Measure Water Hardness: how many grains of hardness is found in your water?

Definition of hard water

As we explain in more detail at WATER SOFTENERS & CONDITIONERS, Water “hardness” refers to the level of unwanted minerals, principally calcium and magnesium, found in your water supply. Hard water is an aesthetic issue (poor lathering, spots on dishes) and a mechanical issue (clogged pipes, expensive repairs, poor washing machine performance) but it is not a health concern.

Photo at left: lime scale fragments collected from a water heater. 

Hard water is found only in certain neighborhoods and usually only on private water supplies from a local well or wells.

At DETECT HARD WATER we describe how to visually detect that your water is high in mineral content or “hard”.

How is water hardness measured?

Water hardness is measured in “grains” per gallon, in milligrams of calcium (Ca) per liter, or water hardness may be expressed in ppm – parts per million, and also in German Degrees of Hardness (dH) [which we drop here as this is for fish tanks].

You can take a water sample to a water test lab to have its hardness measured, but it is also trivially easy to measure the hardness of water yourself, as we explain here.

Readers whose water is acidic or corrosive rather than “hard” and readers needing to know about the Langelier Saturation Index or LSI should

see CORROSIVITY or ACIDITY of WATER.

How to convert among different water hardness measures:

Water with hardness of 25 ppm = 25 mg. of hardness-causing minerals per liter of water.

Table of Degrees of Water Hardness
Soft water	0-17.1 mg/L of minerals
Slightly hard water	16.1-60 mg/L of minerals
Moderately hard water	61-120 mg/L of minerals
Hard water	121-180 mg/L of minerals
Very hard water	more than 180 mg/L of minerals

Notes to the table above

– adapted from web search Wikipedia 01/31/2011

You can compare the water hardness range above with the water hardness test sensitivity of the various water hardness tests listed later in this article.

We repeat this table with more details, below where we show other measures of water hardness..

How to Use A Simple Soap Test to Measure the Grains of Hardness of the Water Supply

You will need:

• a small glass bottle with a tight cap, or a water hardness test kit bottle that is of an ideal size and has a water level line mark on it.
• dish soap
• any measuring device such as a measuring cup marked in ml, cc’s or ounces, or a 12-oz drinking glass

Water hardness can be easily measured using a simple soap test kit that will measure in “grains of hardness” (a little bottle with a line marked on it which you fill to the line with water, add a drop of soap, and shake to look for suds. More drops of soap – more degrees of hardness).

The very crude do-it-yourself water hardness test method that some folks try is just adding dish soap to 12-oz of tap water (the left two columns in our table below).

In our OPINION this is a very crude test and you’d be better off obtaining a free or low-cost but more accurate water hardness test from one of the sources listed below at Water Test Kits & Guide

Water Hardness Measurements – How to Use the Home Soap Test Method for Water Hardness
Test Water Volume – crude test	Soap drops – crude test	Grains/gallon GPG of Water Hardness	ppm mg/LWater hardness in parts per million in milligrams per liter	Softness of the Water
12 oz	10	0 – 1	0-17.1	Very Soft
	20	1 – 3.5	17.1 – 60	Slightly Hard
	30	3.5 07/13/2010 – 07.0	60 – 120	Medium Hard
	40	7.0 – 10.5	120 – 180	Hard
	50	10.5 & higher	180 & over	Very Hard

Notes to the table above

NOTE: 1 German degree of hardness dH = 17.5 ppm. For fish tanks, 200-300 ppm is considered “hard”, 300-500 ppm “very hard” and over 500 ppm “extremely hard” water.

Water Hardness Test Kit – Test Strips

Using simple plastic test strips that carry a chemically-treated pad is an easy and quick way to measure water hardness and / or to confirm that a water softener is working correctly.

LaMotte [cited in detail below] provides a helpful comparison between water hardness measurement using instruments and water hardness measurement using test strips:

Instrument Measurement of Water Hardness: A colorimeter passes a white light beam through an optical filter which transmits only one particular color or band of wavelengths of light to the photodetector, where it is measured.  The difference in the amount of colored light transmitted by a colorless sample (blank), and the amount of colored light transmitted by a colored sample, is a measurement of the amount of colored light absorbed by the sample. In most colorimetric tests, including hardness, the amount of colored light absorbed is directly proportional to the concentration and is reported by the meter.

Test Strip Measurement of Water Hardness:Test strips are typically produced from plastic, with chemically impregnated pads on the end. These pads are designed to react with specific ions and produce a specific color change.  Once a test strip is reacted and a color is developed, the strip is then compared to a printed color chart. The color chart is specifically designed to represent color reactions at various concentrations. Matching the strip to the closest color match produces a concentration reading. – retrieved 12/11/2014, original source:

A step-by-step water hardness test procedure using these test strips and hardness test results are given in detail

at WATER HARDNESS TEST San Miguel de Allende

where we illustrate using the JNW Direct water hardness test kit strips (Amazon.com) to test the hardness level of the water supply in San Miguel de Allende, Guanajuato Mexico (Col. San Antonio) in March of 2019.

What’s the difference between using a total water hardness test strip kit and using the “true calcium” liquid reagent drop count titration method?

Ø  Water hardness or other water test kits are used in a very wide variety of applications beyond simply checking a drinking water supply.

Ø  Some other uses include balancing the water hardness of pools and spas, testing the condensate in a steam boiler system or in water operated cooling towers, and checking the proper operation of water softeners.

Ø  A difference between this calcium test using the dropcount titration method and total hardness test kits that use a test strip is that the test strips only measure total water hardness – which is perfectly fine for examining a residential water supply.

Ø  But for measuring water hardness when maintaining a pool or spa, you need to measure calcium hardness specifically. That measurement requires the drop count titration method described next. Quoting from Taylor who explains the difference in exquisite detail:  … whereas test strips for total hardness have just four or five color blocks to cover a tremendously wide range—from 0 to 1,000 parts per million (ppm) with color blocks for 0, 100, 250, 500, 1,000, for instance—a drop test will allow you to approach the true concentration of calcium hardness in 10-ppm increments.

Ø  This means if you’re faced with wanting to balance water in a spa by increasing the calcium hardness from 60 ppm to 150 ppm, the strip can’t help but the drop test can.9]

Sources of Water Test Kits & Guide to Using a Water Hardness Test Kit

Water hardness test kits may use water hardness test tablets or paper test strips.

When mixed with (a test tablet) or wet by (a test strip such as those shown at left) water of a specified volume (fill the test bottle with the specified amount dictated by the test kit instructions or to the line marked on the test bottle), the water in the bottle plus test tablet changes color (green or red, for example) or the test strip changes color (on a scale, for example) that is compared to a standard provided with the kit. Other simple test kits provide a small glass bottle with a line marked on it and intended for use with dishwasher soap. One drop dish soap at a time. More soap drops = harder water.

We bought our Total Water Hardness Test Kit at Sears where water softeners were sold. Or the hardness of your water may be measured at no charge if you ask the local water treatment company to take a look. A typical water hardness test kit that uses water strips provides with each strip a color chart. Match the color on the strip (after you wet it with your test water) against the color chart to see the hardness of your water sample, measured in ppm or gains.

A typical water hardness test kit strip measures hardness from 0-1000 ppm or from 0-59 grains of hardness.

Potable Water Hardness Test Kits: sources, features, costs: soap, strips, electronic hardness testers are listed here.

Here we describe different methods & prices for building water supply hardness testing and we include description of the different tests, their technology, and their application.

[These water tests are available at Amazon.com through links given here, from the companies and producers listed here, and from other suppliers]

Watch out: a general search for “water test kit” or “water hardness test kit” will list kits and tests that may not match your application. Don’t order an aquarium test kit or a swimming pool test kit if your need is to test building drinking water or potable water supply. The test criteria, methods, and standards may be quite different.

[Disclosure: you can buy these test kits from many online sources including Amazon.com. Amazon pays us a pittance per item if purchased via these links.

Here are our WEBSITE VISITOR PRIVACY POLICY (we do not collect any information about individual website visitors)

• Aquamerck® Mercks total hardness & oxygen content “rapid tests” using the titrimetric method with dropping bottle or titration pipettes for accuracy. Contact Merck or EMD Chemicals in the U.S. or other countries. Merck & Co., Inc. Global Headquarters, One Merck Drive, P.O. Box 100, Whitehouse Station, NJ 08889-0100 USA, Phone: 908-423-1000 – http://www.merck.com/
• Culligan TK-2 Water Test Kit (less than $10. U.S.), includes test bottle, tablets, test strips, instructions. 15-minutes to complete the water analysis testing and determine the chlorine, chloramine, iron, nitrates, hardness, and ph levels.
• Diamond Crystal Water Softening Products: free water hardness test kit: Tel: 800-428-4244. Note: The free test kit distributed by Diamond C.W.S.contains one Hach SofChek test strip which we describe immediately below.
• Hach SofChek Dip-and-Read Water Quality Test Strips: Total Hardness 0-425 ppm, Easy to use test strips – dip and read against a scale on the bottle label. OPINION: Suitable for checking water softener operation – Ed.
• Hach AquaChek Dip-and-Read Water Quality Test Strips, Multiparameter, 50 tests ($20. U.S.) bottle of 50 single-use water test strips, Easy to use. 
  
  Measures well water or potable water hardness in range of 0-425 ppm. Each test strip measures 5 parameters and gives results in a color- change that is matched to references on the bottle label: Free Chlorine (0-4 ppm), Total Chlorine (0-10 ppm), Total Hardness (0-425 ppm – 0-25 grains per gallon of water), Total Alkalinity (CaCO3 0-240 ppm), and pH (6.4 – 8.8). OPINION: Hach is a long-established, reputable water test kit manufacturer; we use this kit – Ed.
• HM Digital TDS-EZ TDS “Water Quality” Tester with Auto-off Function TDS-EZ, HM Digital or Serv-A-Pure Co., (less than $20. U.S.), “water quality” test parameter specifics were not provided.
  
  HM Digital produces a wide range of testing equipment and monitoring equipment. HM Digital, Inc. 5819 Uplander Way Culver City, CA 90230 U.S.A., Website: http://www.tdsmeter.com
  
  Watch out: “Water purity” expressed in parts per million of particulates does not measure water safety, hardness, bacterial nor chemical contaminants.
• Home Water Quality Test Kit, ($41. U.S.), Industrial Test Systems, Inc., ITS produces water test kits & test equipment,
  most expensive test kit in this list, measures for Bacteria, Nitrates, Nitrites, Hydrogen Sulfide, Total Hardness, Total Alkalinity, Total Chlorine, Free Chlorine, Chloride, Copper, Sulfate, Iron, & pH. Industrial Test Systems, Inc., 1875 Langston Street, Rock Hill, SC, 29730 | Toll Free: (800) 861-9712.
  
  Watch out: independent of the actual test reliability, some state health departments (e.g. New York) may not accept as valid the type of bacteria test provided
• Industrial Test Systems, Inc. ITS480008 Total Hardness Water Test Kit, Industrial Test Systems, Inc., ($10.) bottle of 50 water hardness single-use test strips
• Intellitec WPT1000 Digital Water Purity Tester, Intellitec, ($13.), measures “water purity”, readings in ppm of particulates in water.
  
  Watch out: “Water purity” expressed in parts per million of particulates does not measure water safety, hardness, bacterial nor chemical contaminants.

• JNW Direct Hardness Test Strips, Website: jnwdirect.com sold at Amazon at amazon.com/jnwdirect,
  
  See WATER HARDNESS TEST San Miguel de Allende for an example of the use of this the water hardness test strips provided by JNW.

• Jungle Labs Hardness / AlkalinityQuik-Dip Test Strips for Aquariums & fish care.
  
  Watch out: this is an example of a special use product that is not intended for potable water testing.
• PurTest 8-in-1 Iron Hardness Water Test Kit, PurTest, ($16. U.S.), Quoting “PurTest 8-in-1 Iron Hardness Water PLUS Test Kit includes: 3 different foil packet with 2 strips on each packet Test pads Test vial Press on cap”,
  
  tests for Alkalinity, Copper, Hardness, Iron, Nitrates, Nitrites, pH. American Water Service, LLC, Matthews NC, U.S.A., Tel: 800-788-4825, Website: http://www.purtest.com/ Email: water@purtest.com
• Sears, Roebuck & Co., (Kenmore) Free water test. Sears offers free water testing to its customers, testing for hardness, acidity, and clarity.
  
  Fill the bottle with tap water from your building and return it to Sears for a free “in-store” analysis. Or use your own sterile (clean) glass jar with a secure lid, collecting 4 ounces of tap water for this test. Sears will report Hardness in grains per gallon or GPG, clarity (iron or color or sediment), and acidity of your water sample.
• Total Water Hardness Water Test Kit m#480008 [bottle of 50 test strips, available at Amazon.com], produced by Industrial Test Systems, Inc.
  
  A reader comments were critical of a lack of precision in this test with an uncertainty of at least 200 ppm [Jan 2011]; others complained that test strip colors did not resemble the color chart. Easy to use.
• Water Hardness Test Kit, Taylor K-0432, Reagent Pack, Buret, Hardness (calcium/magnesium/total), EDTA, 1 mL = 1 mg CaCO₃
  
  This very thoroughly supplied test kit contains ten components and is designed for expert-level testing of the hardness level of potable water. Like the test reagent discussed next, this kit uses drop count titration for a very accurate hardness measurement. We discuss this kit in more detail below. [9]
• Water Hardness Test Reagent, Taylor R-0012 – 0.75 oz bottle (least expensive test kit in this list but this product contains only the reagent. You’ll need instructions and a 3/4 oz test bottle).
  
  Note that this test kit, sold online at Amazon for “water testing” may be designed to measure calcium levels as necessary for maintaining pools and spas. [9] Discussed in more detail below.
• Micro Essential Lab WHT-050 Hydrion Double Roll Water Hardness Test PaperRolls, 0 to 20 gr/gal and 0 to 50 gr/gal Ranges, Micro Essential Lab, Inc. ($10.) Quoting: Micro Essential Hydrion Water Hardness Tester provides a simple, easy to read test to determine the hardness of water.
  
  This test allows determination of the need to treat the water to prevent calcium carbonate build up and to monitor the ongoing efficacy of the treatment used.
  
  The Tester consists of a roll of Lo Range test paper with a color match chart reading in increments of 0, 5, 10 and 20 gr/gal as calcium carbonate and a wider range roll of test paper with a color match chart reading in 10, 20, 30, 40 and 50 gr/gal of water hardness.
  
  Roll Length: 180 inches. Total Range: 0-50 gr/gal. Micro Essential Labs #: WHT-050. “
• Micro Essential Lab SWT-125 Hydrion Low Water Hardness Test Paper, 0 to 20 gr/gal Range, ($15), Micro Essential Lab,
  Quoting: “Micro Essential Hydrion Low Range Water Hardness Tester provides a simple, easy to read test to determine the hardness of water.
  
  This test allows determination of the need to treat the water to prevent calcium carbonate build up and to monitor the ongoing efficacy of the treatment used.
  
  The Tester consists of a roll of test paper sufficient for approximately 180 tests and a color match chart reading in increments of 0, 5, 10 and 20 gr/gal as calcium carbonate. Total Range: 0-20 gr/gal. 1 Roll/Dispenser; 10 /Carton. Micro Essential Labs #: SWT-125.”
• Watersafe WS425B Drinking Water Test Kit, Watersafe (less than $20. U.S.), tests for Chlorine, Bacteria (?? methodology not stated), Lead, Hardness, Nitrates/Nitrites (fertilizers, animal waste, potentially sewage effluent), pesticides, ten minutes, Quoting: “This WaterSafe kit identifies harmful levels of bacteria and lead in your water.
  
  Watersafe test kits are easy-to-use and produce results on the spot. Tests bring the accuracy of laboratory procedures into any home or business.
  
  Contains one-step water testing kits: Lead kit can detect dissolved lead at levels below the EPA Action level of 15 parts per billion (ppb); bacteria kit can detect the presence of Coliform Bacteria in your water.
  
  Get results in only 10 minutes with easy to follow directions and no mixing or measuring.”
  
  Producer: Discover Testing.com, Silver Lake Research Corporation, P.O. Box 686, Monrovia, CA 91017 Tel: 888-438-1942, Website: http://www.discovertesting.com/,
• Watersafe WS425W Well Water Test Kit, Watersafe, ($25.), Quoting: a single-use kit made for testing well water that will detect coliform bacteria, pesticides, nitrates, lead, iron, chlorine, copper and hardness. Includes an instruction manual and EPA drinking water standards.
  
  Easy to use, with results on the spot.”
  
  Watch out: “bacteria test” may include non-coliform bacteria as well as coliform bacteria, so it is a general indicator, not a comprehensive test.
• Watts Premier 173006 All-In-One Water Test Kit, Watts Premier, ($32. U.S.), color coded test strips, 2 tests for most items, 1 test for some – see this quote: “This test also contains the only available EPA-approved free chlorine test strip on the market! This Water Quality Test Kit includes: * Free Chlorine – 2 tests * Total Chlorine – 2 tests * Chloride – 2 tests * pH – 2 tests * Total Alkalinity – 2 tests * Total Hardness – 2 tests * Nitrate – 2 tests * Nitrite – 2 tests * Iron – 2 tests * Sulfate – 2 tests * Hydrogen Sulfide – 2 tests * Copper – 2 tests * Lead – 1 test * Pesticide – 1 test * Bacteria – 1 test”,
  
  Watts Premier produces a large range of water testing systems, water filtration, water treatment, reverse osmosis, etc.
  
  Watts Premier, Inc. 8716 W Ludlow Dr Ste 1 Peoria, AZ 85381, Tel: 800-752-5582, Website: https://www.wattspremier.com/
  Watch out: “bacteria test” may include non-coliform bacteria as well as coliform bacteria, so it is a general indicator, not a comprehensive test.
• Well Water Test Kit, WellSafe, ($25. U.S.), Quoting, “… test quickly and easily for the most common contaminants found in private well water, including: iron, copper, lead, bacteria, pesticides, nitrates, nitrites, chlorine, pH and hardness.”
  
  Note: We were unable to identify the producing company for this product.
• Water Hardness Test Kit, Taylor K-0432, Reagent Pack, Buret, Hardness (calcium/magnesium/total), EDTA, 1 mL = 1 mg CaCO₃This very thoroughly supplied test kit contains ten components and is designed for expert-level testing of the hardness level of potable water. Like the test reagent discussed next, this kit uses drop count titration for a very accurate hardness measurement. Quoting from Taylor[9]:

Hardness in water was originally defined as a measure of the water’s ability to precipitate soap. In current practice it is considered to be the sum of the calcium and magnesium ions in water, expressed as milligrams per liter (mg/L) or parts per million (ppm) as calcium carbonate.

The modern way to test for hardness is by titration with EDTA (ethylenediaminetetraacetic acid), an organic chelating agent which reacts with both calcium and magnesium ions. When all calcium and magnesium ions are complexed, the excess EDTA reacts with an indicator to give a characteristic blue color, which is the endpoint.[9]

For potable water testing Taylor also provides tests for water alkalinity, water pH, Nitrites, Nitrite, Permanganate (testing water treatment equipment that removes sulphur odors), Sulfites, Iron, Copper, Chlorine, Bromine, Acidity, and a nearly endless catalog of additional water tests and water test methods.

• Water Hardness Test Reagent, Taylor R-0012 – 0.75 oz bottle (least expensive test kit in this list but this product contains only the reagent. You’ll need instructions and a 3/4 oz test bottle). Note that this test kit, sold online at Amazon for “water testing” may be designed to measure calcium levels as necessary for maintaining pools and spas.

How to use the Taylor R-0012 water hardness test kit – drop count titration method

This water hardness test method uses a water hardness reagent, an organic chelant solution whose principal ingredient is Ethylenediaminetetra- 60-00-4 <5 Irritant acetic acid. The reagent is added drop by drop to a quantity of test water and the user looks for a permanent color change in the water test sample.

By using the Taylor R-0012 0.75 oz test bottle and filling the bottle to a mark provided on that container you can be assured that you are using the proper test volume. In discussing water hardness testing (calcium level) in a discussion of pools and spas, Taylor adds these details:

The color progression in a hardness test is from red, to a mixture of red and blue, to blue. To be certain the color change is permanent, indicating you have reached the true endpoint, add one more drop of titrant. If the blue color remains unchanged, do not count this drop.[9]

Taylor also warns about water hardness tests (using a reagent and drop count titration) that produce a “fading endpoint” – the color ends at purple rather than blue due to contamination of the test water by metal ions. The company provides a procedure for adjusting the process if this happens during your test.

Store your reagent between 36-85 degF., keep it out of direct sunlight, and avoid abrupt temperature changes that can cause reagent deterioration. Handle appropriately. Like many acid reagents the liquid can be a skin or eye irritation. Taylor’s website provides an MSDS if you need it. More information is available from the manufacturer, Taylor Technologies [9] whose contact information is at our references section below.

Measuring Water Hardness to Test Water Softener / Water Conditioner Operation using Water Hardness Test Tablets

If you need to confirm that your water softener equipment is working properly you will want to measure the hardness or mineral content of your water supply taken at a plumbing tap (sink faucet) located after or “downstream from” the water softener. The following procedure is adapted from IBC [using “water hardness tablets” and other water conditioner installation manuals.[8]

There are three conceptual data points you might want to test:

1. incoming water hardness – take a water sample from a tap that bypasses or is before the water softener
2. water hardness after a water softener regeneration or “backwash” cycle
3. water hardness a day or more after a backwash cycle, or each day of normal water usage in the building between one backwash cycle and the next one – this can confirm that the settings on the water conditioner controls, including regeneration or backwash cycle frequency are adequate.

• Collect a water sample to be tested from a tap after the water softener if you are performing test #2 or 3 above.
• Place 10 ml of water into a clean plastic bottle – choose a plastic bottle of about 30 ml capacity so that your water sample will fill the bottle to 1/3 full.
• If working with an IBC water conditioner test kit, add one “Yes/No” tablet to the water sample and shake the sample until the tablet has dissolved completely.
• Watch out: do not touch the Yes/No tablet with your fingers, or if you accidentally have done so, stop and wash your hands thoroughly. And don’t put your finger in your eye or mouth.
• Check the color of the water sample. If it is green (of any shade) the water is below 20 mg/L of hardness. If the water sample is red the hardness is 20 ppm or above.