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Difference between hard and soft water

Updated: Jun 3, 2020

Comparison of hard water vs soft water on a water glass
How a standard water glass looks like with hard and soft water

The only thing to realise is that hard water has dissolved minerals whereas soft water doesn’t.

Wait! It can’t be as easy as that, surely?

You’re right. It’s not. Stay with us and you’ll find out the differences between hard and soft water and how you can improve your domestic hard water situation.

What is ‘hard’ and ‘soft’ water?

Water that falls as rain is naturally soft because it comes straight from the clouds. The raindrops dissolve whatever gases or particles are in the air, but that doesn’t make rainwater hard.

The differences depend on the underlying geology of the area where the rain fell. If it’s slate, granite, clay, or other impermeable rock then very few minerals, if any, will dissolve in the water. This is classed as ‘soft’ water. If the rocks are permeable like limestone or chalk the water will contain dissolved calcium and magnesium minerals (among others) and be classed as ‘hard’.

Underground aquifers store water in permeable rocks between the rock grains, giving even more chance to dissolve minerals. Whereas impermeable rocks tend to shed the surface water into streams, rivers, lakes, and reservoirs.

How can you tell which is which?

Well, because hard water contains dissolved minerals rather than suspended particles, you can’t usually tell just by looking. Inspect a glass of hard or soft water and both types seem to be exactly the same.

But they’re not!

What are the differences?

So, we already know that you can’t tell the difference just by looking at the water. But, you can tell by looking at the water’s effects.

There are two main causes of these effects

  1. When hard water evaporates or dries, dissolved minerals stay behind as a precipitate.

  2. The dissolved minerals will come in contact with other types of materials and sometimes chemically react with them.

Let’s look at the effects of hard water.

If you live in a hard water area and you unload your dishwasher, you might see white spots left on the glassware. These are usually deposits of calcium carbonate formed when the water dries out on the smooth surfaces.

Likewise, you may see mineral stains on clothes after being in a washing machine.

Hard water is also harsher than soft, as the water has more suspended abrasive limescale particles. So, clothes wear out a lot faster.

When you wash in hard water, you might feel a film on your hands and face. The chemical reaction between calcium carbonate and soap forms a scum which settles out of solution. You may need to wash for longer and rinse more often if you have hard water.

Washing with hard water contributes to dry and itchy skin. If you wash your hair with hard water, your scalp will feel itchy and your hair will appear dull.

Dissolved minerals change your skin’s pH balance (whether your skin is acid or alkaline). The natural oils in your skin don’t do their job properly and harmful bacteria can grow. Eczema sufferers are particularly susceptible to this.

In case you aren’t sure what pH means, here is a simple chart showing typical pH values of everyday substances.

Simply put, pure water has a pH of 7 (neutral). Rain and soft water are slightly acidic with a pH between 7 and 6.5. This depends on how much dissolved carbon dioxide and sulphur dioxide have been absorbed from the atmosphere. Hard water, on the other hand, is alkaline with a pH of between 7 and 8.5.

pH values of common substances
pH scale of common substances

When your domestic water heating system heats hard water, a small amount evaporates causing the dissolved minerals to precipitate. The solids settle out as limescale on water heating elements and accumulate on the inside of pipes.

Remember that sedimented limescale causes a few problems of its own.

  • Limescale in itself isn’t dangerous to health, but it can harbour harmful bacteria that will contaminate your domestic water if they’re left to multiply.

  • Reducing the pipe bore with limescale reduces the water flow to appliances and taps. Engineers have designed their appliances to work at an optimum water flow rate and pressure. So, when the pipe diameter changes, the efficiency of the appliances drops considerably.

  • Limescale building up on heating elements in showers, washing machines, dishwashers and kettles decreases the efficiency of the element. This results in higher electricity usage and bills.

Soft water is different

Detergent soap produces a good lather and does its job properly when washing clothes and crockery.

Washing your body with soft water allows the soap to do its job and doesn’t leave behind chalky precipitates or scum.

Clothes end up cleaner with no mineral stains. They also don’t suffer from the abrasiveness of hard water precipitate.

Limescale doesn’t form on pipes or heating elements allowing your various appliances to work at their optimum efficiency.

The pH of your skin doesn’t change much, thus preventing attacks from harmful bacteria.

How can we make hard water soft?

Softening hard water and reducing its harmful effects is relatively easy. You just need to remove the dissolved calcium and magnesium minerals.

There are two ways to do this. Either reduce the water hardness as it enters your property using an ion-exchange column or do the job at each appliance so only soft water exits the system.

Fitting ion exchange equipment into the domestic water circuit can be a major upheaval, especially if the water pipework is hidden and out of view. It’s ok if you’re building a new house as the equipment can be incorporated into the architect’s drawings. But, if you’re retrofitting water conditioning equipment, ideally you should fit it to every outlet.

Luckily, appliances such as dishwashers and washing machines have a built-in ion-exchange column for softening water. All you have to do is add water softening salt. Other appliances, like showers, don’t usually have protection but showerheads sometimes have a water softening column. These are in the form of replaceable filter cartridges, but they aren’t always compatible with all shower fittings.

StoneStream showerheads incorporate a filter to remove waterborne particles but also have an optional package to remove hard water minerals. Rather than topping up a salt container like in your dishwasher, you just need to replace the cartridge when it's about to run out, usually between 6 and 10 months depending on the condition of your domestic water. They also have a higher thermal efficiency than others so you’ll reduce any heat losses across the showerhead.

The shower head isn’t the only place in your home to use conditioned water. The water delivered to the taps on the kitchen sink, bathroom basin and bathtub should ideally use softened and filtered water too. If you’re a keen gardener, you should be careful that you aren’t watering the garden with water containing too many chemicals. After all, flowers and vegetables are meant to drink soft rain water, not hard or chlorinated domestic water.

You can buy many types of water filters and conditioners designed for those applications. You can even buy one for the garden hose, although usually allowing tap water to stand for a day or so should be enough to remove chlorine.

If you decide to just treat your shower water however, don’t forget that you might need to install a separate filter such as our universal shower hard water filter to remove as many impurities as possible. This includes not just particles like rust, dirt and limescale but also chlorine, sand and heavy metals.

What next?

If you live in a hard water area or your domestic water contains impurities, it’s a good idea to fit water conditioning units wherever you can. Ideally, install a conditioning unit where the water enters your property. If you can’t do that, install one under the kitchen sink and route the conditioned water to a separate tap for drinking water and washing food. Using specialist water conditioning units will reduce a build-up of limescale around shower head spray holes and around taps. They will also help increase your water flow rate back to where it should be.

It’s also worth looking at our products to see if they can help you improve your showering experience.

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