Water hardness test: three ways to find out how hard your water is
You do not need a laboratory to learn whether your water is hard. A water report, a cheap kit or a simple soap test will get you most of the way.
The easiest water hardness test is to read your water authority's quality report for your area. A home test strip or drops kit gives a quick second opinion. Neither tells you whether the water is safe to drink, only how many minerals it carries.
Hardness matters because of scale. It builds up in kettles, shower roses and hot water systems over the years.
Option one: read the water report
If you are on mains supply, your water authority publishes hardness for each supply zone, usually in milligrams per litre of calcium carbonate. Search your authority's site for its water quality report. This is the best starting point because it covers your actual supply and is not affected by a bad kit.
It does not apply to tank, bore or dam water. Those depend on your own property.
Option two: a test strip or drops kit
Strips are quick and cheap. Dip one in a clean glass of cold water, wait the time on the pack, then match the colour to the chart. A drops kit is a little more precise: you count the drops it takes to change the colour of a sample.
- Use a clean glass and cold water from the kitchen tap.
- Run the tap for a minute first, so you are not sampling water that sat in the pipe.
- Check the expiry date. Old strips drift and give a false answer.
Treat the result as a guide. These kits are not precise enough to base a purchase on.
Option three: the soap test
Half fill a clear bottle with tap water, add a few drops of pure liquid soap and shake it. Lots of suds with a clear layer underneath suggest soft water. Few suds and a cloudy layer suggest hard water. It is rough, but it costs nothing.
What the result means for you
A hard result means scale in the kettle, white marks on glass and a shower rose that blocks. For your hot water system it can mean a shorter life. Read about hard water and your plumbing before you spend money on a fix.
A softener is not always worth it. If your water is only moderately hard and you descale the kettle now and then, doing nothing is a fair answer. Where scale is clearly damaging fixtures, ask a licensed plumber about options. And check the warranty on your hot water system, since some makers set limits on water quality.
Which water hardness test should you use?
| Method | Best for | Limit |
|---|---|---|
| Water authority report | Mains supply, the most reliable starting point | Does not apply to tank, bore or dam water |
| Test strip | A quick, cheap check | Rough guide; old strips drift |
| Drops kit | A little more precision than strips | Still not precise enough to base a purchase on |
| Soap test | A free rough idea | Suds and a cloudy layer only suggest hard or soft |
| Laboratory test | Tank, bore or dam water | Costs more but is the only way to know what is in it |
For mains water, start with the report. Use a kit as a second opinion.
Common mistakes when testing hardness at home
Most wrong results come from small slips. Avoid these and your answer is more reliable.
- A dirty glass. Use a clean one every time.
- Water from the pipe. Run the tap for a minute so you are not sampling water that sat in the pipe.
- Old strips. Check the expiry date.
- Warm water. Use cold water from the kitchen tap.
- Wrong soap. Use pure liquid soap for the soap test.
- Reading too much into it. A hardness result says nothing about whether water is safe to drink.
If the result points to a problem, read water softeners in Australia before you spend money.
Frequently asked questions
How do I test water hardness at home?
Use a test strip or drops kit on a glass of cold tap water, or shake a bottle of water with a few drops of pure liquid soap and check the suds. Your water authority's report is more reliable.
Does a hardness test show if my water is safe to drink?
No. It measures dissolved calcium and magnesium only. Safety needs a laboratory result against the drinking water guidelines.
How accurate are test strips?
They give a rough guide. Expired strips and a dirty glass both throw the result off. Use the water report for your supply when you can.
Do I need a water softener?
Not always. If scale is only a minor nuisance, regular descaling may be enough. Ask a licensed plumber if scale is damaging fixtures or your hot water system.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- NHMRC. Australian Drinking Water Guidelines
- Sydney Water. Water supply, wastewater and stormwater services