What Size Water Softener Do I Need?

When it comes to buying a water softener for your home, size matters.

A water softener that’s too small won’t be able to handle the flow rate of your home’s water system, and could restrict water pressure.

A softener that’s too big is less of an issue, but will cost more money upfront.

What size water softener do I need? This guide will provide you with all the information you need to correctly size a water softener for your household.

👉 Size your water softener in just a few clicks with my Quiz

How to Size a Water Softener

In order to properly calculate the size of a water softener, you’ll first need to gather a few pieces of information:

  • Your water hardness
  • Your average daily water consumption

Water Hardness

Water with a particularly high hardness will result in more work from your softener for the same results.  If you have a well and you have iron (orange staining) you will want to test for that too, since iron content can increase hardness levels.

For this reason, if you live in an area with high water hardness, you’ll want to look at a softener with a bigger grain capacity that can hold enough resin to ensure water softening is a speedy process – and you definitely should look for a softener with enough resin to be able to last a minimum of a week before it needs regenerating.

If your water is hard, but doesn’t have very high levels of hardness, you can opt for a softener with a smaller grain capacity for your home.

Water hardness is measured in grains per gallon (GPG), parts per million (PPM), or milligrams per liter (mg/L).

You can measure water hardness with a hardness testing kit, which you can buy online.

HardnessGrains per Gallon (GPG)Parts per Million (PPM) & mg/L
Soft<10 – 17
Slightly Hard1.5 – 517 – 60
Moderately Hard3.5 – 760 – 120
Hard7 – 10120 – 180
Very Hard>10>180
water hardness scale

Water Consumption

Sizing a water softener should be largely based on how much water you use per day.

After all, if your water softener isn’t capable of keeping up with your water use, it’s no good.

Consider the number of people in your household, the number of appliances in your home, how often these appliances are used, and how this affects your water consumption.

When you are on a municipal or city water supply, It’s a good idea to look at your water bill if you want an idea of your water consumption. It’ll tell you everything you need to know on how much water you use per month. You can then use this information to calculate an average of your water use per day.

If you’re using a higher volume of water per day – and don’t forget that your water-based appliances will have an impact on daily usage – you’ll need a water softener with a bigger capacity.

If your water use per day is lower, you’ll be fine with a water softener with a smaller capacity.

Calculating Your Water Softening Requirements

If, for whatever reason, you don’t have access to your water bill or you are on well water, you can calculate an average daily water consumption by multiplying the number of people in your household by 75.

For instance, you have a family of 3, you’ll need around 3 x 75 gallons (per person), or roughly 225 gallons of soft water per day.

When you know how much soft water you’ll need per day, you can take a look at the next question:

How many grains do I need in a water softener?

If you’ve measured your water hardness with a testing kit, and it’s come up as 10 grains per gallon, and your family of 3 requires roughly 225 gallons per day of soft water, simply multiply 225 (your average daily water consumption) by 10 (your water hardness grain capacity) to find your water softening requirement – in this case, 2,250 grains of daily water hardness.

Because most water softeners are designed for once-weekly regeneration, the next step is to multiply your daily water softening requirement by 7 – for the 7 days of the week.

2,250 x 7 = 15,750. It’s never going to be an exact number, but you don’t need to look for a water softener with this exact grain capacity.

Most water softeners are available as 24,000 grains, 32,000 grains, 48,000 grains and 64,000 grains, so in this example, you’d just round up to a softener with a 24,000 grain capacity.

To size water softener for your own household, use the following formula:

Average Daily Water Consumption x Water Hardness (gpg) x 7 = Water Softener Capacity Requirement

Choosing a Softener to Meet Your Needs

Knowing how to size water softener is important not only for finding the right system for your needs, but also for ensuring your water softener works as efficiently as possible.

Capacity and efficiency are both big things to think about when deciding on which water softener is for you.

Water Softener Capacity

You now know a little about the importance of a water softener’s grains capacity, but what does “grains capacity” actually mean?

A water softener’s capacity is a measure of the amount of hardness minerals it can eliminate from your water before regeneration is needed.

A single grain of hardness measures up to approximately 1/7000th of a pound of dissolved hardness minerals.

So, a water softener that has a 24,000 grain capacity can therefore remove around 24,000 grains of hardness before regeneration – perhaps a little less, as the flow rate and pressure of your water may be different to that used in manufacturer’s laboratory tests.

Again, you can use the calculation above to work out roughly how many grains of water hardness you use per week, and you can then match up your softening requirements with a water softener of the best softening capacity.

Why Efficiency Matters

Some of the best water softeners are certified to NSF/ANSI 44, for efficiency.

According to NSF, efficient water softeners must meet minimum performance expectations for both salt and water.

Efficiency is calculated by comparing the amount of hardness removed from the water with the amount of salt and water needed to regenerate the water softener.

There are many things that can effect the efficiency of a water softener.

One is using a water softener that features timed regeneration. This triggers the system to regenerate even when it still has a good amount of softening capacity left over, just because it has been scheduled to regenerate at this specific time.

This is obviously not ideal, as it means a water softener will be wasting salt before it is even used, which means you’ll need to spend more money on needless top-ups.

The dosage of salt can also affect the efficiency of a softener.

You might think, “the more, the better”, but actually, the more salt you add to a softener, the lower the efficiency. You may even reach a point where the salt levels are so high that they don’t even add to the grains capacity, and they end up being flushed out of the system during regeneration without even being used.

Again, this will only result in you having to spend more money on more of what you didn’t even need to use.

So, you ask, what if I buy a bigger size water softener than what I need? That’s generally fine – as long as you’re sure not to overfill it with salt, and you make sure your system only regenerates when it needs to.

That way, you won’t be wasting salt, which will help you to cut down on costs. You will have to spend more upfront, though.

Related Content: Read our 2022 water softener system cost guide

Common Water Softener Sizes

What size water softener do you need – and what sizes are even available?

The most common system size is 32,000 grains, and most families do find that this is the ideal size for their softening needs, though you may opt for the next size up if your family members are a fan of long baths and showers.

The most common water softener sizes are as follows:

  • 24,000 grains
  • 32,000 grains
  • 48,000 grains
  • 64,000 grains

It’s likely that you’d only need a 64,000 grain softener for commercial use, though some people do use them in their homes if their gallons per day of water consumption is particularly high.

You can also buy water softeners in two different styles: single-tank and dual-tank softeners.

The only real difference between the two is that single-tank softeners provide soft water on demand, while dual-tank softeners provide you with soft water whenever you need it.

So, How Big of a Water Softener Do I Need?

Ultimately, deciding what size water softener is for you comes down to two things:

  1. The hardness of your water, and
  2. Your weekly water consumption

Neither of these figures are anything to guess at.

Find out what your water hardness is by using a testing kit – they cost less than $10 and will give you a much clearer picture of water hardness than by simply checking how well your water lathers with soap.

As for your water consumption, your water bill will give you the best idea of how much water you use on average per day.

If you’ve found a water softener you like the look of, but you’re still not sure if it’s the right size for you, check out the customer reviews. Many people mention their family size and water hardness in these reviews, and how suitable a water softener turned out to be for their needs. And if in doubt, you can always ask the manufacturer.