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If you're struggling with hard water that's staining your appliances or ruining the taste of your drinking water, a water softener could be a savvy investment. But what does a water softener actually do? And how much do you need to spend? Our expert guide answers your key questions.

A reliable water softener can remove damaging minerals effectively from your water supply. So you'll end up spending less to fix or clean the home appliances you use most often.

Below, we take a closer look at how water softeners work, how much they cost and where you can buy them. Plus, we have details on which features to look out for when picking a new model.

If you want a water softener and need help installing it, find a local trader using the Which? Trusted Traders  website.

Water softeners are devices designed to tackle the issue of hard water, where water has a particularly high mineral content (usually calcium and magnesium).

Hard water can be a problem in homes, as minerals contained within the water can create scale and form deposits that clog your pipes. To tackle the issue, a water softener will replace those minerals with softer alternatives (sodium and potassium) through a process known as ion exchange. The machine will also attract and hold on to any positively charged ions, such as iron (which can cause stains).

If your home has hard water, you might find that your water has an unusual taste or smell. Dark stains caused by iron can build up in your toilet, and minerals in the water can make it harder to lather in the shower or bath.

Softer water reduces the risk of limescale, plus it lengthens the lifespan of appliances that use hot water – showers, washing machines and dishwashers, for example. And you won't have to spend as much money on cleaning products to remove limescale and tackle stains.

Water softeners are made up of a mineral tank and a brine tank. They attach to your mains water supply, which means water is softened before it reaches the tap. You'll need to install a water softener at an easy access point – under the kitchen sink is ideal.

The mineral tank contains resin beads and this is where the ion exchange takes place. When the system needs to regenerate, heavy brine solution is drawn from the brine tank and passed through the resin in the mineral tank. The brine tank needs to be manually refilled with salt.

Water softeners can either be time-controlled or metered. Timed models are more basic and generally the cheaper option. They run on a timed interval, which is based on the hardness of the water supply and capacity, as well as the number of people living in the property.

However, timed models can cost more to run in the long term. If the water usage is lower than the calculated amount, it can lead to wasted softened water capacity. If water usage is higher than calculated, water may not be softened sufficiently.

Metered water softeners will regenerate when a pre-set volume of water has been used up – this means there is less waste.

There are a number of websites you can use if you want to check your local area's water supply. 

One such site is Aqua Cure . Simply enter your postcode and it will tell you if you live in a hard-water area. Hard water is measured in parts per million (ppm) and the Aqua Cure website defines soft water as 0-50ppm. Hard water is classed as 201-275ppm.

According to Aqua Cure, hard-water areas are generally found in the South East and parts of Ireland.

Prices will vary depending on the size of the water softener you're looking at – you can expect to spend anywhere between £300 and £1,500. Popular water softener brands include Aqua Cure, BWT, Harvey, Kinetico Kube and Water2Buy.

While the initial cost may seem high, the long-term benefits of owning a water softener will hopefully mean you'll save on repair and cleaning costs.

Ideally, you should check your water softener once or twice a month to see if the salt supply needs replenishing. You should expect to spend between £20 to £30 on a 25kg bag of salt tablets.

If you're shopping for a new water softener, make sure you’re handing over your money to a reputable seller. Check the retailer's returns policy and also have a look at customer reviews. Our advice guide on online shopping has more details.

Popular retailers that stock water softeners include:

Find out which retailers are rated highly by Which? members with our expert guide to the best and worst shops .

Aside from investing in a water softener, there are several other ways to deal with the negative impact of hard water.

To help your appliances last longer, get into the habit of descaling them regularly. See our advice guide on how to descale your kettle and make sure your dishwasher salt is topped up. You can also experiment with water softening products in your washing machine.

Alternatively, you can try fitting a water filter to your taps, as this makes it easier to get lather from soap. A showerhead filter could also be beneficial, as this filters out contaminants and limits limescale.

If hard water and limescale have wreaked havoc on your appliances and you're in the market for new ones, check our guide to the best kitchen appliances .