Green Pool / Algae Recovery Dose Calculator

Two coupled steps. First the shock / SLAM target FC: when you know your cyanuric acid (CYA), we read the target straight off the published FC/CYA shock chart (CYA 50 → 20 ppm, CYA 80 → 31, CYA 100 → 39 — the chart cells, not a round CYA × 0.40, which over-shoots at high CYA), interpolating between cells. When CYA is blank we fall back to the algae-severity target (light 20 / dark 30 / black 30 ppm).

target FC = FC/CYA chart cell (CYA known)  ·  severity 20/30/30 (CYA blank)
FC gap    = max(0, target FC − current FC)
dose      = constant × (volume / 10,000) × FC gap × (reference% / your%)

Then the dose via the operator mass-balance: the product amount scales with your pool volume and the FC gap, and keys off the product's available-chlorine %. Reference constants — liquid chlorine 10.7 fl oz / 10,000 gal / ppm at 12.5%, cal-hypo 1.3 oz at 68%, dichlor 1.57 oz at 56% — flex inversely with the strength you enter, so a 6% jug needs roughly twice the volume of a 12.5% jug for the same FC raise.

This is one pour. A SLAM is iterative — you re-test 3–4×/day and re-dose the gap until three exit tests pass: overnight FC loss ≤ 1 ppm, combined chlorine ≤ 0.5 ppm, and clear water. We give you the target and the protocol; the multi-day tracking stays your job (nothing is saved). Cal-hypo raises calcium hardness and dichlor adds CYA with every dose — so for a stabilized pool, liquid chlorine is the SLAM default. If CYA is over ~70 the chlorine demand is impractical; drain and dilute first.

Two neighbors of this page finish the job. Chlorine alone stalls when phosphates keep feeding the bloom, so the phosphate remover and algaecide dose calculator sizes that side of the treatment, and once the water is clear the chlorine tablet feeder calculator works out the tab load that holds the residual through the rest of the season. On the billing side, a recovery is a project and not a weekly stop, so use the green pool cleanup pricing calculator to turn the chemical mass you just sized into a quote with labor, trips and markup attached.

Sources: PoolChemTracker — FC/CYA Chart (target cells); My Pool Calculator — Pool Shock Dosage (CYA-aware dose + cal-hypo constant); The Pool Nerd — Pool Shock Calculator (severity targets); PoolToolkit / TFP convention (SLAM exit criteria). Dichlor constant is a mass-balance derivation, spot-checked at build.