How to Test Water Hardness (And Why It Matters)

How to test water hardness

You can test water hardness with a simple soap test, over-the-counter strip tests, or a professional water hardness meter. Each method gives you a clearer picture of how much calcium and magnesium is in your water, so you can decide if it’s time to take action.

The soap test involves shaking water and pure liquid soap in a clear bottle to see how well it lathers. Strip tests give you a quick PPM or GPG reading. And for detailed results, a digital meter or lab test is your most accurate option.

Let’s walk through what each one involves – and how to tell what your results actually mean. First up: what exactly is water hardness? 

What is water hardness, exactly?

Put simply, water hardness refers to the amount of dissolved minerals in your tap water (mainly calcium and magnesium).

These minerals occur naturally and aren’t harmful to your health. But when levels get too high, they start to cause problems around your home: stubborn limescale, dull laundry, and that dry feeling after a shower.

Water hardness is usually measured in either parts per million (PPM) or grains per gallon (GPG). The higher the number, the harder the water.

Here’s a quick breakdown from the Australian Drinking Water Guidelines:

<60 mg/L CaCO₃ – soft but possibly corrosive
60–200 mg/L CaCO₃ – good quality
200–500 mg/L CaCO₃ – hard with increasing scaling problems
>500 mg/L CaCO₃ – severe scaling

You won’t always know your number just by looking, but once you do, you can decide whether it’s worth making a change. And in some parts of Australia, it is. 

Are you concerned about hard water? We don’t just need to know how to test water hardness, but why.

Why does water hardness matter?

Hard water isn’t dangerous, but it can be frustrating, costly and uncomfortable to live with.

Over time, those extra minerals can build up inside your taps, pipes, kettles and appliances. That’s what causes white crust on your showerhead, flaky scale inside your kettle, or patchy streaks on your glassware. And the harder your water, the faster that build-up happens.

It can also leave its mark in ways you don’t always see straight away. Like clothes that feel stiff after washing, or skin that stays dry even after a shower.

And the impact adds up. Limescale can shorten the life of your dishwasher or water heater. It can reduce water pressure in your pipes. It makes heating water less efficient, which means higher energy bills in the long run.

In short: hard water quietly wears things down. That’s why testing is worth your time – even if your water looks clear. Because once you know what you’re dealing with, you can do something about it.

Signs you might have hard water

Not sure if your water is hard? There are a few common signs to watch for.

Soap that doesn’t lather easily – you need more product to get the same result
White spots on glasses or cutlery – especially after using the dishwasher
Crusty build-up on taps, shower heads or kettles – a telltale sign of limescale
Dry skin and dull hair – even after showering or washing with quality products
Laundry that feels rough or looks faded – hard water can reduce fabric softness
Low water pressure – caused by scale narrowing your pipes over time

If you notice one or more of these, it might be time to test your water hardness. The good news? It can be quick, easy, and something you do yourself – starting with a simple soap test.

How to test for hard water

Testing water hardness with strip tests

Strip tests are a great next step if you want a quick reading with real numbers. You can find them at most hardware stores or online. They’re affordable, easy to use and surprisingly effective. Just fill a clean glass with cold tap water, dip the strip for a few seconds, and compare the colour change to the guide on the pack.

Most strips will give you a result in parts per million (PPM) or grains per gallon (GPG). Here’s how those results typically line up:

Soft – under 60 mg/L
Good quality – 60–200 mg/L
Hard – 200–500 mg/L (expect some scaling)
Very hard – over 500 mg/L (expect more severe scaling)

It’s not lab-accurate, but it gives you a clear starting point. If your result creeps above 200 mg/L, it may be time to protect your plumbing, appliances and fixtures. Are you wondering how to improve water quality at home? See our guide on how to filter tap water.

Next up: what to do if you want the most precise result possible.

Professional testing for water hardness

If you want the most accurate reading of your water hardness, a professional test is your best bet.

There are two main options: a digital water hardness meter (which you can buy online or from plumbing suppliers), or a lab-based test where you send a sample off for analysis. Both will give you a precise result—usually in parts per million (PPM)—and in the case of lab testing, you’ll often get a full breakdown of other minerals and contaminants, too.

This option is especially useful if:

You live in a region known for hard water (like parts of WA or SA)
You’ve noticed persistent limescale issues
You’re planning to install a water filter or new kitchen tap and want a clear starting point

Knowing how to test water hardness is important. And so is understanding the results. Let’s make sense of the numbers, so you know what to do next.

Understanding your results

Once you’ve got your water hardness result—whether from a strip test, meter or lab—you’ll see a number, usually in milligrams per litre (mg/L). But what does that actually mean for your home?

What soft water means (under 60 mg/L)

Soft water won’t leave limescale behind, but it can be slightly corrosive to pipes – especially if your plumbing is older. It can also give water a flat or slippery feel. If you’re in this range, there’s usually no need to take action, but filtering can still help with taste and clarity.

What good quality means (60–200 mg/L)

This is the sweet spot. You might see minimal residue in your kettle or on your taps over time, but it’s unlikely to cause issues. If you live in this range and still notice scaling or taste changes, the cause may be local plumbing or other water chemistry factors.

What hard water means (200–500 mg/L)

This is where things start to show. You’ll likely see more limescale in your kettle and around fixtures, and may notice dry skin, flat hair, or detergent that doesn’t lather well. Appliances like dishwashers and hot water systems can wear out faster in this range. In these cases, it’s worth considering a filtration or pre-treatment system.

What very hard water means (500+ mg/L)

If your result is above 500, scaling becomes an ongoing maintenance issue. Without intervention, scale can build up in pipes, reduce heating efficiency, and shorten the life of your appliances. A limescale pre-filter, combined with high-quality water filtration, is often recommended in these conditions.

Managing hard water at home

Once you know your water is hard (or very hard), it’s worth thinking about how to protect your home from the impact.

There are a few ways to do that. Some people install a whole-house water softener, which replaces calcium and magnesium ions with sodium. These systems are effective, but they’re large, expensive, and not always suitable for every household.

A more targeted solution is to filter the water you use most – especially for drinking, cooking, and appliances like kettles and dishwashers. This is where Zip Water comes in.

A smarter solution for everyday water

Zip HydroTap systems use MicroPurity filtration to filter down to 0.2 microns. That’s fine enough to reduce eight of the most harmful contaminants you can't see, smell or taste in your water, including microplastics, asbestos and lead – along with 99.4% removal of PFAS*. 

They also include a built-in limescale inhibitor, protecting your system from the inside out – and giving you cleaner, better-tasting water at the same time.

In hard water regions like WA and SA, a limescale pre-filter is recommended for extra protection. It works alongside the HydroTap to reduce mineral deposits and extend the life of your system.

At its core, the HydroTap is a filtered water system – but it’s a lot more than that. It gives you boiling, chilled and sparkling water instantly. No kettles. No waiting. And no single-use bottles cluttering up the fridge.

Are you curious to know more? Explore the Zip HydroTap range, or learn more about hard water vs soft water. 

If you’re after something that tastes better, works harder, and fits seamlessly into your space – Zip makes the switch easy.