How to Size a Water Softener For Your Home [4 Factors]

If you’re getting residue on your plates, soap scum in your sink, and dry skin after a shower, there’s a good chance you’ve got hard water. But you’re not alone. Around 85% of American households use hard water for their everyday needs.

female checking her dry skin
Having dry skin after shower can be due to hard water

Unfortunately, hard water can cause problems around your home and affect the efficiency of your water appliances – which is why people turn to water softeners.

Not only can they improve the quality of your drinking water, but they can also prevent mineral build-up in your showerheads, kettles, and taps. This means that dishes, clothes, and skin will feel softer and cleaner – and you won’t need to upgrade your pipes all the time!

But there are a lot of water softeners out there and it’s hard to know what the difference is. Why do they come in different sizes? Is bigger better? In this article, we explain what a water softener does and why hardness and consumption are critical to finding the right size for your household needs. Let’s get stuck in!

What is a Water Softener?

A water softener is a filtration system that removes dissolved minerals, such as calcium and magnesium, from your water supply. These minerals, which occur naturally in our oceans and soils, have a tendency to bond with metals, which is why you get hard deposits in pipes and showerheads – hence the name “hard water.”

Luckily, magnesium and calcium don’t pose any health risks – unless you have a history of kidney stones, in which case you could get recurrences.

The most common problems, however, are difficulty with lathering up your hair or achieving a residue-free finish on plates or cutlery. At worst, the mineral build-up can obstruct water flow, reduce pressure, and corrode your pipes over time – leading to expensive repairs or replacement.

That’s where water softeners come in.

These handy units use negatively charged resin beads to attract the positively charged minerals and remove them from the water. The demineralised water then flows through your pipes and out of your tap. This process continues until the resin beads reach maximum capacity.

When this happens, the unit is flushed with salt or potassium chloride from the brine tank. This washes the minerals from the resin beads and discharges them through a hose. The system then reverts to its softening function again and the cycle continues.

How Big Should My Water Softener Be?

The size of your water softener depends on two key factors: the hardness of your water and daily consumption. Let’s find a closer look.


The first thing you need to do is find out how hard your water is. Depending on where you live, your water supply will contain a range of different minerals. The most compound is calcium carbonate, which is usually found in marble, limestone, and chalk.

This isn’t surprising. Calcium carbonate formed over millions of years from the sedimentation of shells and coral – and it now comprises four percent of the earth’s crust. However, the amount in your soil or water is not uniform. If you look at the map below, you’ll see how concentrations of calcium carbonate vary from state to state in the US.

The amount of calcium in your water supply

Other minerals like magnesium, copper, iron, and zinc can be present in your supply too. It all depends on the quality of the soil where you live, as well as run-off from rain and floods.

To measure your water’s hardness, you can buy a water-testing kit, request a quality report from your water supplier, or use an independent laboratory to test a water sample. The results are measured in milligrams per liter (mgL) or grains per gallon (gpg). You can find both measurements in the chart below.

slightly hard61–1203–7
very hard180+11+

Once you have your hardness value, it’ll give you an indication of whether your water is hard, soft, or somewhere in between. Keep this value handy as you’ll need it when we use the water softener calculator later on.


The next step is to calculate how much water you use. Analyse your water bill for the last few months and make a note of the total gallons used. There may be fluctuations between seasons, so find an average you can work with.

If you don’t have access to this data, use an estimate. According to USGS, the average person consumes 80–100 gallons of water per day. Use this figure and multiply it by the number of people in your home. Note: If you take short showers and don’t water the garden, go with 80 gallons; if you think your consumption is higher, go with 100 gallons.

So, if you have a four-person household that averages 80 gallons each, your daily consumption total is 320 gallons.

Water Softener Calculator

Now that you have the hardness number and your consumption in gallons, you’re ready to use the water softener calculator. The formula is pretty simple. You multiply the hardness number by the gallons per day.

For example, if you have four people using 320 gallons in total and the hardness is 8, the total would be 2,560. This means that your water softener would need to remove 2,560 grains each day.

Hardness value x Total gallons per day = Grains to be removed per day

Example: 8 gpg x 320 gallons = 2,560 grains per day

If your water has a lot of iron, increase the total hardness value by 3 gpg per 1 mg of iron, then make your calculation. If these figures are making your head spin, just use this easy water softener sizing calculator.

How Do I Choose the Right Water Softener?

Grain Capacity

Water softeners are sized to indicate how many grains are removed before regeneration. On average, this happens every seven days. Common sizes are 24,000, 32,000, 48,000, 56,000, and 64,000 grain capacity. However, it’s wise to choose one that exceeds your weekly consumption by about 30 percent to allow for excess usage.

For example, if you were using 2,560 grains per day, this would total 17,920 grains per week. In that case, a 24,000-grain capacity softener would be suitable.

Most homes use a 32,000-grain capacity, but if your water is very hard and you’ve got a large family, you may need to buy a softener on the higher end of the scale.


This depends on the size, brand, and features, but it can vary between $300 and $4000. Look for models that let you know when salt needs to be added, or that regenerate at night when water consumption is low.

You can also get a salt-free model to comply with local regulations (some states ban salt water softening systems) and reduce salt content in drinking water – but prepare to pay more.

If you want on-demand soft water, you can even get a twin tank where one tank goes offline while it regenerates and the second tank provides softened water. But keep in mind that these units are expensive to run and need to regenerate more frequently.

Can a Water Softener Be Too Big?

Generally, you should get a water softener that’s slightly bigger for your needs – but not too big.

If a water softener is too large for your household, it won’t regenerate often enough, which can damage the resin beads and promote bacterial growth in the tank. Also, big tanks, consume more water and cost more upfront.

But don’t undersize your water softener, either. This could result in insufficient soft water for your household and frequent regenerations. This can use more salt and shorten the life of your resin beads – and your water softener.

What is a Good Number for Water Hardness?

When you look at our chart, anything between 0–3 gpg is ideal for water. If you set your water softener to the current hardness value of your water, it will remove grains to achieve this optimal range.

When it does, water will feel silkier and plates will look shinier. It can even make your meals or drinks taste better. That’s because the high concentration of minerals won’t interfere with other flavors. Having said that, water will still contain traces of these minerals after softening.

That’s not necessarily a bad thing. According to WHO, drinking water can be a beneficial source of calcium and magnesium for people who lack these minerals in their diets.

Can You Install Your Own Water Softener?

If you’re replacing an old water softener with a new one, chances are you’ve got all the fittings in place. All you have to do is switch out the old softener for the new one. This should be a relatively easy DIY job that can be completed in a couple of hours. 

For those who’ve never had a water softener, installation will involve some pipe cutting and soldering. You’ll also need to be familiar with local plumbing codes to ensure that your work is compliant. For instance, some states require you to fit shut-off valves in case of emergency.

If you’re eager to take on the challenge, see the video below for step-by-step instructions.

Of course, not everyone will have the confidence or skills to undertake this kind of work. If that’s you, find an installer and they’ll do the job quickly and professionally. The cost could be anywhere between $300 and $1500, depending on the size of the unit, where it’s located, your state, and the complexity of the job.

Final Thoughts

Buying the right-sized water softener can improve the quality of your drinking water and the efficiency of your water appliances. All you need are two simple values: water hardness and daily consumption. Then, using the calculation provided above, you can work out how many grains per gallon need to be removed on a weekly basis – and which size can help you achieve this.

While getting a unit that’s 30 percent larger will cover you during high-usage periods, anything bigger than this will result in infrequent regeneration that can damage your resin beads and breed bacteria. You’ll also pay more for a much larger unit. Instead, try to stick to the guidelines we’ve given you. It’ll prove cost-effective in the long run, and ensure the longevity and efficiency of your water softener.

We hope this article has answered your questions about how water softeners work and why size matters! Check out the articles below for more household guides and hacks. 

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