Reviews and General Information
on the Best Water Treatment Systems Around
SoftWaterFiltration is supported by our readers. When you purchase an item through links on our site, we may earn an affilate commission.

What Size Water Softener to Choose?

What Size Water Softener to Choose?

So it’s time, you’ve finally had enough of scrubbing at the lime-scale build-up around your faucets, on your toilets and just about every other surface that comes into contact with the hard water in your home. Perhaps the final straw was that you’ve spent your hard earned cash on repairing your dishwasher or washing machine, only to be told this time around it has to be replaced. All down to hard water.

I feel your pain. I also understand that the journey you’re just about to undertake (or have been on for some time) isn’t easy either. Knowing what size of water softener you should have is one of the most complicated things I’ve come across, and I’m sure glad I paid attention in my Math classes.

Essentially, there are two elements to the equation you’re about to learn and that’s:
how hard your water is and how much water your household uses.
This (I’m afraid) is where it can get a bit complicated, but I’m here to help.

Measuring Water Hardness

Now you might think you have very hard water because the lime-scale build-up is especially bad on your surfaces. However, this doesn’t necessarily mean the level of hardness isn’t moderate rather than extreme. The reason for this hasn’t got anything to do with your housekeeping, it’s down to your pipes. If you have a particularly old water system which hasn’t been checked in a while the build-up inside could have reached epic proportions which will be transferred through your faucet.

There are a couple of ways you can measure the level of hardness in your water. You can approach a local laboratory which will take a sample of your water and test it for you. However, the results can take time and it can also be expensive.
One of the easiest ways to go about this (your first task) is to get a water hardness testing kit. More information can be found on this by visiting my water test kits page.

You should know the level of water hardness is measured in grains. So when you see the abbreviation “gpg” this means grains per gallon. The more grains, the harder the water is.

Below, I’ve added a classification table to give you an idea of what the results mean (I also included the mg/L / ppm measure).

water hardness table

Knowing How Much Water you Use

This isn’t an exact science, and the chances are you will always have to work with an average. After all, there are times when you use more water than others.
So, just to give you an idea, the average person uses about 70 to 90 gallons of water per day.

All you need to do is multiply this by the number of people in your household.
For example, 4 people = 280 gallons per day.

The Size of Water Softener Required

Once you know the level of hardness in your water and have an idea of how much water you’re using, it’s time to calculate the size of water softener you will need.

To make the numbers easier to understand, let’s say you use 250 gallons of water per day, and the amount of grains per gallon is 6.
6 x 250 = 1500 grains and this is the magic number because that’s what your water softener has to achieve in order to make it effective enough to make a difference.


As you may already know there are varying capacities of water softener on the market, so we’re not done yet. Say for instance you need to remove the amount of grains detailed above and you opt for a 30,000 grain capacity softener.

This will easily deal with the 1500 grains you need to remove each day, but you have to bear in mind how often you will need to regenerate your system with salt.

This is the last calculation (I promise).
What you need to do as per the example above is divide 30,000 by 1500 which gives the answer 20. This means you will need to regenerate every 20 days.

Hopefully by now, you have some idea of what size of water softener to choose and I apologize if it’s made you reach for the headache pills. However, it’s vitally important you get the right size or you could be spending an inordinate amount of money on salt (as regeneration usually takes between 5 and 10 lbs of salt).

Back to Top