The Investigator Series #3: Water Forum - Water Softener Sizing Case Study
In this particular forum, I’ve had several back-and-forth “discussions” with another frequent contributor about applying and sizing water softeners. I respect all points of view—we can always learn something. This contributor leans traditional or “old school,” and we ended up with opposite recommendations.
Let’s break it all down. We’ll explain the systems suggested and how The Water Softener Blog applies our four cornerstones—Advocacy, Expertise, Methodology, Education—to resolve the problem and find the best, most efficient solution for this home and family.
Household Profile & Water Analysis
- Water analysis: 21 gpg hardness, 1 ppm ferrous iron, pH 7.4, TDS 427, no sulfur/odors, no bacteria.
- Occupancy: Six people, including the in-laws.
- Fixtures: 4.5 baths; 4 showers.
- Laundry: Two washing machines.
- Kids: Ages 10 and 12; both play sports.
- Basement: Finished walkout with workout room, family room, bathroom, and small kitchen.
- Water heating: Three 50-gallon heaters.
- Plumbing: 3/4″ copper throughout.
- Existing unit: Single-tank 45,000-grain softener (served prior family of four + occasional in-laws).
- Estimated demand: ~15,000 grains of softened water per day.
- All of these factors determine the most efficient softener size and type.
Calculator Result & Sizing Logic
The Water Softener Blog has a free water softener calculator app to help you choose the right system for your family (linked below). Using the calculator:
21 gpg hardness + (1 ppm iron × 4 gpg) = 25 gpg total compensated hardness
For six people, this points to a ~48,000-grain single-tank softener. We round to a common configuration: 45,000 grains (1.5 cu. ft. resin) requiring about 15 lb of salt per regeneration.
Options Discussed on the Forum
- 45,000-grain single tank
- 45,000-grain twin tank
- 120,000-grain single tank
This household would use approximately 15,000 grains/day of softened water.
Option 1: Fleck 3/4" 5600 Metered 45k Single-Tank
- Reserve capacity: 15,000 grains (one full day), leaving ~30,000 grains of operating capacity.
- Regenerates ~every 2 days using 15 lb salt and 85 gal water per regen.
- Approx. monthly use: 225 lb salt, 1,160 gal water.
- ★ Average internet price: $850 for a Fleck 5600 metered 48k.
Option 2: Clack 1" Metered 45k Twin-Tank (Alternating)
- No reserve needed—alternating tanks provide soft water 24/7, including peak demand.
- Regenerates ~every 3 days using 15 lb salt and 40 gal water per regen.
- Approx. monthly use: 150 lb salt, 400 gal water.
- ★ Average internet price: $2,300 for a Clack 48k twin-tank.
Option 3: Fleck 2510 1″ Metered 120k Single-Tank
- Reserve capacity: 15,000 grains; operating capacity ~105,000 grains.
- Regenerates ~every 7 days using 60 lb salt and 200 gal water per regen.
- Approx. monthly use: 260 lb salt, 800 gal water.
- ★ Average internet price: $4,600.
- Often won’t fit typical residential basements.
- Requires higher regeneration flow than many homes can supply.
- The suggested valve may not efficiently backwash or fully regenerate 120k resin.
- Other drawbacks exist but are beyond this post’s scope.
Why the Twin-Tank Stands Out
With no reserve penalty and continuous soft water during peak usage, the 45k twin-tank reduces monthly salt and water compared to the 45k single—and avoids the size/flow pitfalls of a 120k commercial-scale unit.
How We Applied Our Four Cornerstones
Advocacy
We start by listening—family size, schedules (sports & laundry), fixture count, and future needs—then advocate for what fits their life, not our inventory.
Expertise
We convert iron to hardness, size reserve properly, and match valve/tank to real-world flow rates so the system operates and regenerates efficiently.
Methodology
We use our calculator-based approach, validate the water analysis, and compare options on operating capacity, salt/water use, and lifecycle costs.
Education
We explain the “why” behind each recommendation so homeowners can make confident, informed decisions—and enjoy great water for decades.
We helped this customer based on the four principles of "The Water Softener Blog": Advocacy, Expertise, Methodology, and Education.
Figures for salt/water use and prices are from the forum discussion and typical settings; actual results vary by configuration, resin, and local conditions. Always confirm peak flow rates and drain capacity before selecting a water treatment system.
I wish you Good days and Good water!
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Thank you, Ray