3 easy ways to find out how hard your water is (and why it matters)

So, you know you’ve got hard water — your kettle’s crusty, your shower screen is cloudy, and your soap just doesn't get soapy. But just how hard is your water?

Knowing your exact water hardness isn’t just a fun fact — it can help you choose the right filters, protect your appliances, and tackle limescale before it becomes an expensive headache.

The good news? You don’t need a chemistry degree or a lab coat. There are a few easy ways to test your water hardness at home — and we’ll walk you through them.

1. Use hard water test strips

The simplest and most reliable method is to grab a pack of hard water test strips. They’re cheap, easy to use, and surprisingly accurate.

Here’s how they work:

Dip the strip into a small glass of water for a few seconds, then compare the colour change to the chart that comes with it. This gives you a reading in mg/L (milligrams per litre) of calcium carbonate — which is the standard way water hardness is measured in the UK.

They’re ideal if you want to check different taps around the house, compare water before and after installing a filter, or track changes over time.

We recommend SimplexHealth Total Hardness Water Test Strips, because they're easy to use and give clear water hardness readings:

Amazon £3.99 ➡

2. Check your local water supplier’s report

In the UK, water suppliers are required to publish water quality reports — and some may include information on hardness levels. Search your supplier’s website or contact them directly and ask for the calcium carbonate levels in your area.

This gives you an average reading — helpful for general guidance, though it won’t show what’s happening at your exact tap.

3. Use postcode-based hardness checkers

Some water softener and filter brands offer online tools that estimate water hardness based on your postcode. These tools can be useful for getting a quick snapshot — though they’re usually based on wider regional data.

If you’re curious, try:

Harvey Water Softeners’ checker

Phox Water postcode tool

Just take the results with a pinch of salt — they’re not always precise, and it’s best to double-check with a test strip or supplier data.

How is water hardness measured?

In the UK, water hardness is usually measured in mg/L of calcium carbonate (CaCO₃). The higher the number, the harder the water.

According to the Drinking Water Inspectorate (DWI):

Soft: up to 100 mg/L

Slightly hard: 100–150 mg/L

Moderately hard: 150–200 mg/L

Hard: 200–300 mg/L

Very hard: over 300 mg/L

Why bother testing how hard your water is?

Hard water = high levels of calcium and magnesium — and those are the minerals behind limescale. They’re also what can leave your skin feeling dry, your hair limp, and your appliances struggling.

When you know your water’s hardness level, you can choose the right shower filter or drinking water filter, know whether to descale your appliances more or less frequently and understand whether a water softener is worth the investment.

In short, it helps you make smarter decisions — and spend less time battling scale.

✨ Limescale lowdown ✨

• Hard water means higher levels of calcium and magnesium — and yes, that’s exactly what’s behind the limescale in your kettle, shower head, pipes, and heating system.

• You can find out how hard your water is with a quick postcode check on your water supplier’s website, or get a more accurate result using at-home test strips (they’re cheap, fast, and surprisingly satisfying to use).

• Once you know your number, it’s much easier to choose the right solution — whether that’s a simple white vinegar soak, a shower filter upgrade, or a full-blown water softener.