Does your house have ‘hard’ tap water?  Hard water can cause a variety of concerns and nuisances for you and your house, including white spots on washed utensils, shower doors and glass ware, as well as plumbing problems, and film build up on tubs and shower doors.  It can also dry out your skin and hair.

As a solution, many homes chose to invest in a water softener.  But how do you know what sort, and what size, water softener you need for your home?

In this article, we explain the different considerations to weigh when figuring out the size of water softener that will work best in your home.

What is a Water Softener?

A water softener works by removing the mineral ions (usually magnesium and calcium) and inserting salt in their place, leading to ‘softer’ water.

The softener typically filters your water as it comes into your home from the source, meaning that it will soften all the water in your home.

Water softeners work through a process called ion exchange.  When the hard water enters into the system, it flows through a bed of resin beads, which pull out with calcium and magnesium ions from the water.  Sodium ions are then released when the resin attracts the mineral ions.

In essence, the ‘hardness’ of the water is stripped out as it passes through the mineral tank, leaving softer, less mineralized water to flow into your home.

The water softener in a condominiumWhat Size Water Softener Should I Purchase?

When it comes to figuring out the size of water softener you need, you can follow a simple formula.  First, take the total number of people in your household, and multiply that by the average number of gallons they use daily.  In the U.S., the average person uses about 80-100 gallons per day, according to the U.S. Geological Survey.

So, if you have a family of 4 people, you would multiply 4 x 80-100 to get an estimate of 320-400 total gallons used per day.  For what it’s worth, most of this use comes from high water use appliances, like taking showers, running a dishwasher, or flushing the toilet.

From there, the next step is to multiply the water usage estimate by a measure of the grains of hardness that is present in your water.  For some background, water hardness is typically measured in ‘grains per gallon,’ or gpg.  It is also sometimes measured in parts per million (ppm) or milligrams per litre (mg/L).  1 gpg is equal to about 17.1 mg/L or 17.1 ppm.

To determine the relative hardness of your water, you can contact your local municipality or water provider.  Alternatively, you can purchase a water hardness test kit, which is sometimes the only viable option, if a private water supply is being used.

To give a sense of scale, slightly hard water typically has 1-3.5 grains per gallon.  Medium or moderately hard water might have around 3.5-7 grains per gallon.  And very hard water has a range of about 7-10 grains per gallon.

So, as an example, let’s say we are living with very hard water at around 10 grains per gallon, with a family of 4 consuming about 400 gallons per day (better to be on the safe side).  That would mean we are in need of a water softener capable of handling 4,000 grains per day.

Water Softener Regeneration

Now we have our daily estimate of our water softening requirement.  But we’re not quite done yet.  Since we don’t want to have to refill our softeners with salt everyday, but we still want to ensure that they are doing their jobs efficiently, most manufacturers design their softeners with about a week’s regeneration cycle in mind.

You might be wondering, what is a regeneration cycle?  In essence, it’s the term used to describe the flushing out of the collected minerals that it has extracted from the hard water that has passed through the softener.

At a certain point, the softener has trapped all the hardness minerals it can handle and becomes saturated.  At that time, it needs to be flushed out and cleaned such that it can continue to soften new water.

This matters for water softener sizing because it gives us a timeline to plan around.  If we have a water softener that needs to regenerate every 7 days, then we know we need to multiply our 4,000 grain per day softening requirement by 7.  The end result is that we need a softener capable of softening about 28,000 grains between regenerations.

Typically, a family of 4 will use a 32,000 or 24,000 grain capacity water softener.

Water Softener Efficiency

In addition to household water softening needs, a note should also be made regarding water softener efficiency.  Efficiency speaks to how much salt is required to run a water softener at its maximum capacity.

Efficiency is significant because oftentimes a lot of salt is needed to run a softener at its full capacity, and so you can potentially benefit by purchasing a softener that has the ability to filter out more grains than you require, but buying less salt.

Accordingly, this is equivalent to putting up more money up front for a larger softener, knowing that you will be able to save on salt costs down the line.  Over the entire lifespan of a water softener, buying a higher salt efficiency softener will save you time and money.

For example, let’s say that your water softening requirements are around 21,000 grains per week.  You could easily buy a softener that filters in the 24,000 grain level.  However, it will take a large amount of salt – in the neighbourhood of 25+ pounds – to fully regenerate the machine such that it can filter the full 24,000 grains.  Similarly, a 32,000 grain capacity machine takes about 35+ pounds of salt every time it regenerates to get the full grain capacity.

However, using less salt in a larger machine, say about 6 pounds of salt in a 32,000 grain machine, will get you about 20,000 grains of softening.  This is because larger capacity machines have more resin, and thus even when they operate with less salt, can still provide a fairly high degree of softening.

As a reference, what most manufacturers and distributors call a 32,000 grain machine has about 1 cubic foot of softener resin.   A 48,000 grain machine has about 1.5 cubic feet, while a 64,000 grain machine will have about 2 cubic feet, and so on.  But remember, this assumes the lowest salt efficiency setting, meaning the highest amount of salt is used, costing you more in the long run.

Running on the highest salt efficiency (that is, using the least amount of salt possible), a softener with 1 cubic feet of resin will have about a 20,000 grain capacity, a softener with 1.5 cubic feet will have about a 30,000 grain capacity, and 2 cubic feet of resin will yield approximately 40,000 grains.

So before you make a decision on sizing your water softener based purely on the water requirement, be sure to consider your long term salt costs.

Sizing Your Water Softener

So what size water softener is best for you?  In a nutshell, it depends on the water softening needs in your household, and the efficiency of the water softener itself.