Grain capacity from your water hardness, iron and household size, plus every install part and the cost.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
| Plumbing & Heating | $554–$750 |
| Total | $554–$750 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
The Water Softener Calculator sizes the system from the same numbers a dealer would ask for — your water's hardness in grains per gallon, how many people the house serves, and how many days you want between regenerations — and turns that into a grain capacity, a mineral tank size, and a resin bed rather than a guess pulled off the smallest box at the hardware store. Dissolved iron gets folded in too, since it consumes exchange capacity the same way hardness does, right up until it doesn't.
From there it prices what a grain rating alone leaves out: the resin itself by the cubic-foot bag, a brine tank sized to your salt dose, a bypass valve so the house can run on hard water during service, the drain line and code-required air gap, and a sediment pre-filter for well water. Choose metered or timer-based regeneration and standard or high-capacity resin, and the salt use, resin cost, and every downstream part update together.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Get an actual hardness and iron reading rather than guessing — a home test strip is fine for hardness, but iron benefits from a lab or dealer test since ferrous and ferric iron behave differently in a softener. Run those numbers through the calculator with your household size to get a grain capacity and tank size.
Choose a spot on the main line after any whole-house sediment filter and before the water heater, with room for both the mineral and brine tanks, a nearby drain, and an electrical outlet for the control head.
Close the main shutoff, drain the line at the lowest fixture, then cut into the supply line and install the bypass valve assembly that lets the house run on hard water during future service.
Level the mineral tank, add the resin through the top opening per the manufacturer's instructions, and connect the control head to the bypass valve's inlet and outlet ports.
Set the brine tank alongside the mineral tank, connect the brine line between them, then run the drain line to your chosen discharge point through the saddle valve and air gap fitting.
Plug in the control head, set the current time, and program hardness, iron and regeneration settings to match what you sized — metered heads also need the household's water meter reading entered so they can track actual usage.
Fill the brine tank with the first bags of salt to the manufacturer's recommended level and add a few gallons of water to help the first brine solution form.
Open the bypass to service position, run a manual regeneration cycle, then check for leaks at every new connection and test the softened water's hardness at a downstream tap to confirm the system is actually working.
Equip the job
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Keep planning
Interior & Finishing
Answers
Size comes from total grains of hardness removed per day — your water's hardness in grains per gallon times how many gallons the household actually runs, plus dissolved iron converted to an equivalent hardness load — multiplied by how many days you want between regenerations. That total picks the smallest standard mineral tank and resin bed that covers it, which is a real capacity number, not a rule of thumb like 'one cubic foot per bathroom.' Bigger households or harder water push you to a larger tank; longer regeneration intervals do too, since the resin has to hold more capacity between cycles.
Dissolved (ferrous) iron consumes resin exchange capacity almost the same way hardness does, so this calculator folds it into the daily grain load using a standard 4-grains-per-ppm rule of thumb. But there's a ceiling: past roughly 3 ppm, iron starts fouling the resin bed faster than normal backwashing clears it, and iron that has already oxidized to a rust color won't come out through ion exchange at all — that needs a dedicated iron filter or oxidizer ahead of the softener, not a bigger resin bed.
Standard 8% crosslink resin is the default in most residential systems and costs less per cubic foot. High-capacity 10% crosslink fine-mesh resin exchanges more hardness per cubic foot at the same salt dose, which lets a smaller, cheaper tank do the same job — worth it in tight utility closets or very hard water where a standard-resin tank would size up a full tier. It costs more per cubic foot, but you typically need less of it.
Salt use scales with resin volume and how often the system regenerates — this calculator reports both the pounds used per regeneration and a starting quarter's supply in 40 lb bags. Salt pellets are the cheapest and most common choice; solar salt crystals dissolve a bit more evenly and cost slightly more; potassium chloride avoids adding sodium to the discharge (relevant on a sodium-restricted diet or a sensitive septic field) but runs three to four times the price of sodium-based salt for the same softening result.
On well water, yes — grit, sand and rust flakes are one of the most common reasons a resin bed loses capacity years before it should, and a pre-filter is cheap insurance against all three. On a treated municipal supply the risk is lower, but a pre-filter still protects the control valve's internals from whatever sediment does slip through, especially after any nearby water-main work stirs up the line. It's the smallest line item on this list relative to what it protects.
Backwash discharge routes through a saddle valve on the drain line to a floor drain, laundry standpipe, or a dedicated line — wherever your local code allows. The air gap fitting is required in most jurisdictions because without a physical break in the line, a drain backup or pressure change could theoretically siphon wastewater back into the softener and, from there, the house's fresh water — a small, inexpensive fitting that closes a real code gap.