There is no need to make it complicated; how to test for water hardness in Australia is more straightforward than one might think. You can have a quick read on it with a liquid soap test, get a better estimate from some test strips, or put it to a laboratory test where precision is required.
Raymond Vale here. I like my household advice to be plain about what you should do, what pitfalls to avoid and when to put down the test kit. For the most part water hardness is not a safety issue, but the dissolved calcium and magnesium will put a film of scum on your glassware and showerheads, build up limescale in kettles and hot water systems and leave white deposits. See mineral deposits in hot water units for more detail.
In this guide I set out how to test hard water in the home and interpret results in ppm or mg/L, how to check water hardness by postcode across Australia and the case for a professional test or softener.
What Does Water Hardness Mean?
Put simply, it is the measure of dissolved magnesium and calcium. The figures are often given as parts per million (ppm) or milligrams per litre of calcium carbonate (mg/L as CaCO3). In water 1 mg/L and 1 ppm are one and the same.
Hard water will not let you get many suds from your soap and leaves something behind; heat it and limescale is likely. Soft water has less of these minerals but do not assume “soft” is synonymous with better tasting or cleaner. Advertising would have you believe otherwise but water chemistry is not so dramatic.
The following table offers a way of classifying hardness for the purposes of a household comparison, if not an Australian health standard.
| Hardness Result | Common Description | Likely Household Effects |
|---|---|---|
| 0–60 mg/L as CaCO3 | Soft | Little scale, good lather |
| 61–120 mg/L as CaCO3 | Moderately hard | Some film from soap, now and then a deposit in the kettle |
| 121–180 mg/L as CaCO3 | Hard | Spotting, less lather and an increase in scale |
| 180+ mg/L as CaCO3 | Very hard | Cleaning becomes an exercise in dealing with scale |
A Liquid Soap Test
Before any outlay on equipment, the liquid soap test is the economical means of seeing if you have a problem. It will not be exact but you will see if the water from your tap is of the hard or soft variety.
To be fair in your assessment, use the same volume of water and glass and the same soap. Should you be putting two properties head to head, do so in identical containers and in like conditions or you are comparing apples to garden hoses.
Procedure
- Take a clear jar or bottle and put in 250 mL of cold tap water.
- Ten drops of unadulterated liquid soap should do it. Put the antibacterial and exfoliating products aside, as well as any hand wash with moisturiser.
- Give the container a good shake for 10 seconds or so.
- Examine the water under the bubbles. If the water is fairly clear and the bubbles hold, it is soft. Cloudiness, a grey-white film and a paucity of bubbles point to hardness.
- Do it again on another sample if you are in any doubt.
Soap and hard water form insoluble compounds which is the reason for the dull film in the bath and the extra soap needed for a lather. But be aware that the formula of the soap, how clean the bottle is and your technique in shaking it all play a part, so consider this a screening.
Where The Test Falls Short
One sees it done wrong with a large squeeze of soap and a lot of foam to judge. Even hard water will make a cloud of foam if you put enough in; a measured dose is preferable.
Nor can it tell you if the hardness is due to calcium or magnesium, and it is of no use in detecting salinity, bacteria or lead. If there is a question of taste, odour or health, this is not sufficient.
Test Strips
For something between a soap test and having it done in a lab, water hardness test strips are the sensible option. Dip them in a sample and the reactive pad will change colour to be read off the printed scale. Any water hardness test kit you come by in a hardware or water-treatment store in Australia, or order online, will have the strips and the necessary instructions and chart. Not every Bunnings will have the same water hardness test kit in stock, so do not make that assumption; a look at what is on offer in store or online will tell you.
Get A Cleaner Strip Result
To obtain a cleaner result from your strip, let the cold tap run for a while first of all, should it have been left alone overnight. A glass is to be preferred over testing under the tap itself. Be sure to adhere to the packet’s stipulated dipping time as leaving the strip in the water any longer will throw off the colour.
Then put the strip in the light the instructions call for and make a quick comparison. Note down the outcome and if the reading is ambiguous between two bands, do it again another day. Make separate tests of mains, filtered and rainwater tank taps where they are to be had.
While test strips serve well to compare sources or see if a treatment system is doing its job, they are of limited value if the colour blocks are too close or one requires a defensible figure for a medical decision, commercial equipment or a matter with a plumber.
On the subject of TDS meters
A common question is how to use a TDS meter for water hardness. The thing is, a TDS meter is an indirect measure of total dissolved solids via electrical conductivity, nothing more. It will not give you the calcium carbonate hardness directly.
The reading can be made up of sodium, potassium, bicarbonate, chloride and other things in solution as well as calcium and magnesium. So you could have two samples with identical TDS yet one has more sodium and the other more calcium and magnesium.
Where TDS Helps
Where a TDS meter is of assistance is in registering a broad change in the source, say between unfiltered and filtered water, or for monitoring consistency. But there is no way to turn a TDS number into a hardness result with any reliability unless there is a proven correlation for that supply.
Do not go out and get one to find out if the kettle is due for descaling; leave that to a laboratory test or a hardness strip. There is no substitute for a sample taken in the proper manner and put through a recognised method by a lab for the most accurate assessment of water hardness, as opposed to some attractive figure on a digital display.
Mg/L and Ppm
You will see results put forward as mg/L or ppm as CaCO3 in a report. They are one and the same for all intents and purposes when testing ordinary water: 100 mg/L equals 100 ppm. “As calcium carbonate” is merely a convention of reporting.
Have a word with the test kit’s categories before anything else. Colour bands are not always the same from one maker to the next. If the strip indicates 120 to 180 ppm then so be it, there is no point in putting down 143 ppm. False precision is false even in a lab coat.
And for household purposes one should take the symptoms into account. An 80 mg/L reading might be of no consequence in one house but leave spots in another depending on the soap, the temperature of the water and how the fixtures are looked after.
Hardness by postcode
One cannot assign a national water hardness to an Australian postcode. From private bores and groundwater to the various treatment plants, the figures will differ from city to suburb. What a neighbour finds is indicative at best.
Your local utility or water-quality section is a good place to begin. Put in your supplier, be it Urban Utilities, Melbourne Water or Sydney Water, along with your postcode and suburb and you will come across data on alkalinity, total dissolved solids, calcium and so forth.
Build A Local Water Picture
Some utilities will put out typical ranges for an area instead of a street by street result. In that case your own test with a strip will indicate where your home falls.
Postcode maps are fine for an initial guess but they can be reductive and may not reflect changes to the network. Rely on the latest report from your area and put any odd results to the test.
The National Health and Medical Research Council’s Australian Drinking Water Guidelines are the framework for drinking-water quality in this country and a sound reference, though a hardness result is no barometer of overall safety.
Spot Hard Water Around Home
If in doubt as to whether the effort of testing is justified, walk around the home for some physical evidence. Anywhere the water is heated or has evaporated will show you the minerals.
- White deposits on the kettle or about the tap aerator and showerhead.
- Glassware that comes out of the wash with a cloudy film.
- Soap scum you have to put in some effort to remove.
- Perhaps the shower does not put out as much water as it should.
- Scale has formed at the hot-water outlet and heating elements.
- Skin or hair left feeling dry, though one cannot put all such symptoms down to hardness.
Take the showerhead for instance. When I began to look into the issue of hardness I was taken aback, not by the kettle but by it. The spray was uneven; I put it down to the fitting until I saw the chalky stuff inside. A good clean and soak would do for the time being, yet a test made plain why it was always back.
Do not be quick to label any white mark limescale. There is soap residue, grout dust, corrosion and cleaning products that will pass for it. An inspection and another test cost less than a new tap.
When to call in a professional
If you need more than just a hardness reading, or the water has an odd taste or smell, or the source is a private tank or bore, have a professional run a water test. The same applies if your results are at odds with one another. A laboratory will check hardness in conjunction with other indicators.
It is prudent to have this done before putting in an expensive softener, especially when one is going by a postcode estimate. You want treatment equipment to be in keeping with the household size, the way you use it and the actual chemistry of the water. An overzealous softener can bring its own water-quality and maintenance headaches.
Be sure to collect your sample in accordance with directions. Put it in the container provided without handling the lid or interior, make note of the time and which tap, and see to it the sample is cool if the lab so requires. Enquire as to whether they are accredited for what you need and if the figure will come back as mg/L as CaCO3.
Choosing your next move
For a strip test to see what is behind the white flakes in the kettle, that is fine. But where you are pitting one source against another, do it on the same day. Should you be thinking of a treatment system, get a laboratory report and measure it up against the manufacturer’s specifications.
A softener will cut the hardness but is not de rigueur. A blocked aerator in need of replacement, a change of cleaning product and some descaling will address most domestic annoyances. Mineral deposits in hot water units may be due to hardness but then again the age of the plumbing, the temperature and how well it is looked after will play their part.
Frequently Asked Questions
Here are the answers to the ones that trip people up. In short, home tests are for screening purposes, the laboratory is for making complicated decisions and settling matters.
Can I do my own testing?
You can. Water hardness strips or a soap test will give you a rough idea of the range. Be meticulous with the instructions and put an inconclusive result to the test again. It is no substitute for a proper water-quality assessment.
Where can I find a map of Australian water hardness?
Not one exists that will show you the exact figures for each postcode. Rely on local utility reports for the supply area. Mains water and a private bore or rainwater collection nearby are quite different things.
What is the surest way to check?
Have a reputable lab analyse a properly obtained sample and ask for the hardness in mg/L as CaCO3. Do not expect precision from a soap test and a TDS meter is not a hardness instrument.
Testing at Bunnings?
Check the pool-testing, plumbing or water-treatment aisles for a kit or strips, depending on what is in stock. Have a look at what is on offer before you make the trip and read the instructions. Make certain the scale is telling you the hardness and not merely the chlorine, pH or TDS.
Is hard water something to worry about?
Not in itself. Hardness is a measure of dissolved magnesium and calcium. Whether the water is safe to drink is a function of physical, chemical and microbiological considerations. If you have a particular concern, consult your supplier’s report or have it tested.
To make the exercise worthwhile
Proceed in a logical fashion at home: a liquid soap test to start with, strips for a number, and leave the analysis to the lab if it bears on a purchase or health. Be consistent in how you take the sample and record the units. A TDS reading is not a hardness result.
Some checking of this kind will account for a recalcitrant showerhead or spotted glasses and the kettle. And it will save you from laying out for a softener when a better test and a clean aerator would have sufficed.