Is my area hard water? How to check in a couple of minutes

It's one of the first things people ask us on a survey visit: "Is our water actually hard, or is it just the kettle?" Fair question. If you live in London or the South East the answer is almost always yes, but it's worth knowing roughly how hard, because that decides whether a softener is worth it and how it should be set up. Here's how to find out without buying anything.

The tell-tale signs

Your house will usually give the game away before any test does. Have a look for these:

• A furry kettle. White or brown flakes in the bottom, or bits floating in your tea.
• Crusty taps and shower heads. A chalky white build-up round the spout, and shower jets that spray off sideways.
• Cloudy glass. Shower screens that never look clean, and glasses that come out of the dishwasher spotty.
• Soap that won't lather. Shampoo and shower gel need a bigger squeeze, and there's a grey scum ring round the bath.
• Stiff towels. Laundry that dries scratchy, even with fabric conditioner.

If you're nodding along to three or more of those, your water's hard. The question is how hard.

Check your postcode

The quickest way to get a number is to look it up. You've got two options.

Your water supplier

Every supplier publishes water quality information by postcode. In London that's mostly Thames Water or Affinity Water, with SES Water, South East Water and Essex & Suffolk Water covering parts of the surrounding counties. Search your supplier's site for "water quality" or "hardness" and pop your postcode in. This is the most accurate figure you'll get without a test, so it's worth doing.

Our postcode checker

Our hard water postcode checker gives you a rough figure in a couple of seconds, along with an estimate of how much sodium your water would contain once softened. The numbers are an approximate guide to what's typical for your area rather than official supplier data, so use it for a quick sense check and then confirm with your supplier.

What the numbers mean

Hardness is usually given in milligrams per litre (mg/l) as calcium carbonate. Suppliers don't all use exactly the same wording, but these are the bands we use:

• Soft: up to 50 mg/l
• Moderately soft: 51 to 100 mg/l
• Slightly hard: 101 to 150 mg/l
• Moderately hard: 151 to 200 mg/l
• Hard: 201 to 300 mg/l
• Very hard: over 300 mg/l

You might also see Clark degrees (divide mg/l by 14.3) or German degrees, °dH (divide mg/l by 17.8). They're just different units for the same thing. A lot of softener control panels and test strips use one of these, which is why it helps to know the conversion.

Most of London lands in the hard or very hard bands. That's down to geology: much of the water has soaked through chalk and limestone, picking up calcium and magnesium on the way. There's more on that in our guide to hard water areas in London.

A test at home

If you want to see it for yourself, a cheap hardness test strip from a DIY shop or online will give you a ballpark reading in about a minute. Run the cold tap for a bit, dip the strip, and compare the colour to the chart. They're not lab-accurate, but they're fine for telling "a bit hard" from "very hard".

The old-school version is the soap test. Half-fill a clear bottle with tap water, add a few drops of pure liquid soap (not detergent), put the lid on and give it a good shake. Lots of bubbles and clear water means soft. A thin layer of bubbles and cloudy water means hard. It's not scientific, but it's a fun one to do with the kids.

And if you book a survey with us, we test your water on site for free. We need the exact figure anyway, to set a softener up properly.

Does the number change?

A bit, yes. Your hardness can vary from street to street, and it can drift through the year depending on which sources and treatment works are feeding your area. So don't worry if your supplier's figure and a test strip disagree slightly. The band matters more than the exact digit.

So is a softener worth it?

Here's our honest rule of thumb. If your water's in the soft or moderately soft bands, you almost certainly don't need one. In the slightly or moderately hard bands, it depends on how much the limescale bothers you. In the hard or very hard bands, which is most of London, a softener makes a real difference to cleaning, appliances and how the water feels.

A softener isn't the only answer, mind. Some people are happy descaling the kettle and wiping the taps. If you'd like to know what it would look like in your home, have a read of how water softener installation works. We'll always fit a separate unsoftened drinking tap in the kitchen too, and our post on drinking softened water explains why. If you're weighing up cheaper options, have a look at our comparison of a water softener or scale reducer.

If you've just moved here from a soft-water part of the country, the difference can be a bit of a shock. Our guide to moving to London from a soft-water area covers what to expect. And for what hard water does behind the scenes, read limescale and your boiler.

Quick answers