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TheBlueprintof Water
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Three flows, each used exactly once. The vessel is sized to the flow the system delivers.

Operating Case

Three flows, each used exactly once. Results update automatically.

ModeSize a new softener from the flows, or check a vessel you can measure against the flow it receives.
ArrangementThe first decision. Duplex alternating is the default for boiler makeup; progressive when the peak is many times the average; single almost never on a boiler.

Duplex alternating, but check the low-flow flux (R = 3.2). A peak-sized vessel spends much of its life below the green floor.

Flow through the softener while the makeup valve is open. Measure it if possible: trigger the DA fill valve and clock the softened-water makeup meter. Estimate it with the True Pipe Flow Calculator.
gpm

Measure it if you can. Or estimate it with the True Pipe Flow Calculator.

Turndown R = 3.2, recommendedDuplex alternating check the low-flow flux
Annual-average softened makeup. If this feeds a boiler, use the makeup rate from the Boiler Blowdown Calculator.
gpm

Annual average. Boiler makeup if it feeds a boiler.

How much higher the busiest month runs than the annual average. These are starting estimates; with monthly makeup or gas data, compute peak month over the 12-month average and enter it.
Peak-month average day over annual-average day. Not the single worst day; sizing for one extreme day oversizes the vessel.
×

Peak-month day over the annual-average day.

The standard vessel the drawing and the cards read. Best viable follows the verdict table; pick any row to compare.

Each vessel full size in a duplex.

Total hardness of the water entering the softener.
mg/L

mg/L as CaCO₃. Iron adds to it.

Dissolved iron loads the resin like extra hardness, about 4 gpg for every ppm Fe.
ppm

ppm Fe, 0 to 10.

Pounds of salt per cubic foot of resin at each regeneration. 15 lb/ft³ is the usual choice for boiler makeup where low leakage matters.
lb/ft³

30.0 kgr/ft³ at this dose.

Effective Hardness
Hardness plus 4 gpg per ppm Fe226 mg/L

13.2 gpg with the iron.

Capacity held back so the softener regenerates before hardness breaks through: makeup hardness above design, demand above forecast, meter error, the gap to a time-clock regeneration. It does not bridge a regeneration outage. 10% is standard; lower it with a metered head and steady water, raise it on a time clock or variable supply.
%

10% in every arrangement, and yours to set. It guards against breakthrough before the trigger, not the regeneration outage.

Design Windows (Spec 1 B5)Service flux: green 5 to 10 gpm/ft², red under 4 or over 12Volumetric flux: green 2 to 4 gpm/ft³, red under 1.5 or over 5Backwash: 5.0 gpm/ft² at 55 °F, temperature correctedRegeneration at peak: green 1 to 7 days (twin from 0.5)Race: yellow under 4 regenerations of run, red under 2
Flow available to backwash the bed. Defaults to the instantaneous flow; override if backwash draws from a different source.
gpm

Flow the plant can send to drain.

Affects the backwash rate. Cold water expands the bed more, so it needs less flow; warm water needs more.
°F

35 to 100 °F.

Backwash, brine draw, slow rinse, and fast rinse together. About 1.5 hours is typical; check it against the controller's cycle.
hr

Backwash, brine, and rinse.

Click on any check to learn more.

Duplex alternating on the 30 × 72

Each vessel passes the full 40 gpm. Three independent checks, never one status light.

Operating Conditions
Mode
Size
Arrangement
Duplex alternating
Instantaneous
40 gpm
Peak Day
18,000 gal
Effective Hardness
226 mg/L
Salt Dose
15 lb/ft³

Key Results

The vessel, its three checks, the envelope, and the salt.

Salt is 0.556 lb per kgr in every arrangement: the second tank costs no more salt.

Selected Vessel The tank on the drawing, its resin, and the worst of its four checks.

30 × 72 in

15 ft³ resin, 4.91 ft² bed, each of two

green overall. The best viable row; pick another in the case or the table.

Service Flux The instantaneous flow over the bed area, and over the resin. Green from 5 to 10 gpm/ft² and 2 to 4 gpm/ft³.

8.15 gpm/ft²

2.67 gpm/ft³, green

green: green from 5 to 10, red under 4 or over 12.

Regeneration Days between regenerations at the peak month, which sizes capacity. One to seven days is the comfortable band; a twin may run to half a day.

1.70 days at peak

4.26 days at the annual average

green. System rate; each vessel regenerates half as often.

Regeneration Race A duplex must finish regenerating before the lead exhausts: yellow under four regenerations of run, red under two. A single reports its outage instead.

40.9 hr per run

vs 6.0 hr (4 × 1.5 hr regen)

green. Three independent checks, never one status light.

Envelope The diameters that hold the flux window at this flow, the resin the flux and the target run need, and the backwash the plant must supply.

27.1 to 38.3 in

resin 10.0 to 20 ft³

Capacity ≥ 238 kgr a run for a 1-day run at peak; backwash ≤ 40 gpm.

Salt Price Your delivered salt cost per pound.
$
per lb
Annual Salt Cost$2,891

19,272 lb a year, 482 bags, from 2,628,000 gal of makeup.