How To Properly Size A Water Softener

by Jay | Updated on April 21st, 2023

Water softeners are a must-have for many households dealing with hard water. But how do you know which size is right for you?


In this comprehensive guide, we’ll walk you through everything you need to know about properly sizing a water softener, complete with practical examples and helpful tips. Let’s get started!

Why Size Matters: The Consequences of Improper Sizing

When it comes to water softeners, size matters. Choosing the wrong size can lead to a host of problems, such as:

  • Undersized Water Softener: An undersized unit won’t produce enough soft water for your daily needs, leading to hard water bypassing the system. It also causes the resin beads to regenerate frequently, reducing their lifespan.
  • Oversized Water Softener: An oversized unit doesn’t regenerate frequently, which can damage the resin bed. It also results in higher costs due to unnecessary capacity.

The 5-Step Process to Determine the Right Size

Properly sizing a water softener involves a simple 5-step process. We’ll break down each step and provide practical examples to make it easy for you!

Step 1: Determine Your Water Hardness Level

Water hardness is graded on three levels: “hard,” “moderately hard,” and “soft,” based on calcium carbonate levels. It’s measured in ppm (parts per million), mg/L, or gpg (grains per gallon). The industry standard is gpg, and you can convert ppm to gpg by dividing by 17.12.

How to Measure Water Hardness:

  • Use a test kit for a DIY test at home.
  • Visit a laboratory for professional testing.

Example: Your water hardness test shows a level of 10 gpg.

Step 2: Calculate Your Daily Water Volume

Estimate your family’s daily water consumption by checking your water bill or using the average water usage per person (80 to 100 gallons per day).

Example: A family of 5 using 80 gallons per person daily: 80 x 5 = 400 gallons of water per day.

Step 3: Determine Your Daily Softening Requirement

Calculate how many hardness grains need to be removed daily to provide soft water.

Formula: Daily Softening Requirement = Water Hardness (gpg) x Daily Water Volume (gallons)

Example: 10 gpg x 400 gallons/day = 4,000 hardness grains per day.

Step 4: Calculate Your Ideal Total Grain Capacity

Your water softener should regenerate approximately every 7 days for optimal performance.

Formula: Total Grain Capacity = Daily Softening Requirement x 7

Example: 4,000 grains/day x 7 days = 28,000 grains per week.

Step 5: Consider Salt Efficiency

Salt efficiency is expressed as grains/pound of salt rating. It shows how many hardness grains are removed per pound of salt. You don’t need to regenerate 100% of the salt, as it increases costs. Aim for around 84% regeneration.

Example: A 33,000-grain unit requires 14.1 lbs of salt to regenerate 100%, but with 8.3 lbs of salt, you can regenerate 27,600 grains (84%).

Other Factors to Keep in Mind: Flow Rate and Water Softener Types

  • Flow Rate (GPM): Consider the flow rate, especially for larger families, to avoid hard water slipping through during peak consumption times. Check the GPM (gallons per minute) of showers and appliances.
  • Types of Water Softeners: Be aware of the different types of water softeners available, such as salt-based, salt-free, and magnetic. Each type has its own characteristics and sizing considerations.

Let’s Put It All Together: Practical Scenarios

To make this guide even more practical, let’s walk through a couple of scenarios:

Scenario 1: Small Household

  • Water Hardness: 8 gpg
  • Number of Occupants: 3
  • Average Water Usage per Person: 80 gallons/day

Using the 5-step process:

  1. Water Hardness: 8 gpg
  2. Daily Water Volume: 80 x 3 = 240 gallons/day
  3. Daily Softening Requirement: 8 gpg x 240 gallons/day = 1,920 grains/day
  4. Total Grain Capacity: 1,920 grains/day x 7 days = 13,440 grains/week
  5. Salt Efficiency: Aim for a unit that regenerates approximately 84% with efficient salt usage.

Recommended Water Softener Size: A unit with a grain capacity of around 15,000 to 18,000 grains.

Scenario 2: Large Household

  • Water Hardness: 12 gpg
  • Number of Occupants: 6
  • Average Water Usage per Person: 100 gallons/day

Using the 5-step process:

  1. Water Hardness: 12 gpg
  2. Daily Water Volume: 100 x 6 = 600 gallons/day
  3. Daily Softening Requirement: 12 gpg x 600 gallons/day = 7,200 grains/day
  4. Total Grain Capacity: 7,200 grains/day x 7 days = 50,400 grains/week
  5. Salt Efficiency: Aim for a unit that regenerates approximately 84% with efficient salt usage.

Recommended Water Softener Size: A unit with a grain capacity of around 55,000 to 60,000 grains.

Wrapping It Up: The Key Takeaways

Properly sizing a water softener is essential to ensure optimal performance, longevity, and cost-effectiveness. By understanding your water hardness level, daily water consumption, and softening requirements, you can confidently choose the right size for your household. Whether you have a small family or a large one, the right-sized water softener will provide you with soft, high-quality water for years to come.

Jay

Jay is a health and wellness enthusiast with expertise in water quality and nutrition. As a knowledgeable advocate for holistic well-being, Jay successfully manages Type 2 Diabetes through informed lifestyle choices. Committed to sharing reliable and authoritative insights, Jay combines firsthand experience with a passion for enhancing health."