Knowing the proper water softener size for your needs is important before investing in a unit. In this post, we’ll focus on the two key factors in determining the right size water softener.
At the end of this post, you’ll be walking away with the knowledge of what size a water softener will fit best with your household.
What size water softener do I need?
The size of water softeners is marketed in terms of grain capacity (GR). This is the amount of hardness that a water softener can remove before its resin bed and resin beads need to be regenerated. The most common softening capacity for water softeners falls between 24,000 GR and 80,000 GR. But it is also possible to find softeners of up to 110,000 GR.
Arriving at the right water softener capacity for your needs will require you to calculate the daily water softening requirement of your household. And this is where the two definitive factors come in. To accurately calculate this, you’ll need to know the hardness of your water and your household’s water consumption.
Why is it important to know the right size for water softeners?
Miscalculating the size of water softener you need can have you spending a lot more than you would have if you calculated correctly. How much salt you’ll need to use, and the amount of soft water needed by your household are just two of the affected matters by the size of a water softener. This is true for either getting a size smaller or a size bigger than what you require.
If you get a size smaller than what you need, your water softener will be going through the regeneration cycle a lot more often. This means your softener will go through a lot more salt in a short amount of time, as the resin beads will exhaust faster. Your water bill will also be affected by the regular regeneration cycles.
If you get a size bigger than what you need, you’ll be shelling out a lot more money. Bigger capacity water softeners will cost more. While you will go through less salt and water use will also be less, an oversized water softener still won’t be saving money.
The ideal scenario is getting the right water softener size. You’ll go through regeneration cycles at a normal pace, achieve maximum salt efficiency, have minimal to moderate water waste, and have a constant supply of soft water.
How to properly size a water softener
Most households only need a 32,000-grain capacity water softener system. Knowing how to arrive at the proper size for a water softener is valuable to ensure you’re getting the system you need. And to do that, you’ll need to consider the two definitive factors on how to size a water softener.
This first factor is the number of hardness minerals (mostly calcium and magnesium) dissolved in your water. The main function of water softeners is to remove hardness ions and produce soft water. Once you get a unit of your own, the softener will require the hardness value for programming.
So, it’s important to know your exact water hardness when considering what size water softener to get. Trying to guess the number may leave you with an inefficient and improperly sized water softener.
How is water hardness measured?
Water hardness can be reported in grains per gallon (gpg) and milligrams per litre (mg/L) or parts per million (ppm).
Units of Water Hardness
Water chemists use parts per million to measure impurities in water. This is interchangeable with milligrams per litre since 1 ppm is equal to 1 mg/L.
Grains per gallon is a unit of water hardness where 1 grain (64.8 milligrams) of calcium carbonate is dissolved in 1 US gallon (3.785412 L). This is the industry standard for discussing water hardness.
1 gpg is equal to 17.12 mg/L (ppm). So, if your water tests arrive in mg/L, divide it by 17.12 to convert it into gpg. It can also be said that a “grain” of water hardness is 1 pound per 7000 gallons.
Measurement of Water Hardness
This degree of hardness standard was established by the Water Quality Association and the American Society of Agricultural Engineers.
- Soft: <1.0 gpg or <17.0 mg/L (ppm)
- Slightly Hard: 1.0-3.5 gpg or 17.1-60 mg/L (ppm)
- Moderately Hard: 3.5-7.0 gpg or 60-120 mg/L (ppm)
- Hard: 7.0-10.5 gpg or 120-180 mg/L (ppm)
- Very Hard: >10.5 gpg or >180 mg/L (ppm)
How can you determine your water’s hardness?
To measure water hardness, you have two options. You can test for water hardness or get the hardness level from your local water utility.
Being connected to the municipal water supply will make things easier for you. For most cities, city water utility annual reports are available online. From these reports, you can determine the water quality that reaches your household. If this info isn’t available, you’re left with the first option. Water test kits are fairly accessible and can help you determine the hardness of your water, as well as detect the existence of contaminants.
Once you get your hands on the report, see if iron is present in your water. If it is, the hardness value needs to be adjusted. You’ll need to add 3 gpg of hardness to the total value for every 1 mg/L (ppm) of iron.
The second factor you need to consider is how much water is consumed by your household. A large family will consume more than a household of two. Knowing the accurate amount will help you determine what size of water softener you need.
Similar to hardness levels, water consumption isn’t something you should just guess. Doing so will be risking buying a water softener that cannot meet the daily softening requirement of your household.
How can you determine your household’s water consumption?
The most accurate way to determine your household’s water consumption—specifically, daily consumption—is to look at a water bill. You’ll most likely find info for total consumption for a month. From there, you can calculate how much water your household consumes on average per day.
If this info is unavailable to you at the moment, a quick way is to use any number between 80 to 100 per person in your household. According to the United States Geological Survey (USGS), this is the average number of gallons a person uses per day.
How to calculate your daily water softening requirement
To calculate your daily softening requirement, you’ll need the hardness level of your water and your household’s daily water consumption. You can use the example calculation using the following formula below to determine your requirement.
Hardness: 10 gpg (note: 10 is the average for hardness)
Daily Water Usage: 4 people x 90 gallons/day = 360 gallons/day
Daily Softening Requirement: 10 gpg x 360 = 3600 grains per day
This example shows how many grains need to be removed per day for a household of four, which is 3600 grains per day. Note that optimal regeneration occurs for most water softeners every seven days. With that, you’ll need to multiply the daily softening requirement by seven to determine the exact grain capacity you need in a water softener.
Weekly Softening Requirement: 3600 grains per day x 7 days = 25,200 grains per week
And voila! This tells us that the example household needs a water softener with at least a 25,200-grain capacity.
Hopefully, our discussion helped you answer “What size water softener do I need?”—specifically the water softener capacity you should be looking for. As for the cost, check out one of our posts to learn about several factors affecting the cost of efficient water softeners.
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