PoolCare Tools

Methodology and source register

Pool dosing advice is safety-relevant, so we publish our workings. Each constant below lists what it is, where it comes from, what we have cross-checked, and what still needs to happen.

StatusCountMeaning
Verified math4Deterministic math or unit conversion. Provable in one line.
Industry standard7Published industry formula. Presented with its source, not as our own advice.
Awaiting credentialed review2Not published as guidance until a Certified Pool Operator reviews and signs off. See review policy.

The register

gal-per-ft3

Verified math

1 ft³ = 7.48052 US gallons

SourceStandard US liquid-volume conversion (NIST Handbook 44, US customary liquid gallon)
Cross-checks
  • 1 US gallon = 231 in³; 1 ft³ = 1728 in³ → 1728/231 = 7.48051948…

l-per-gallon

Verified math

1 US gallon = 3.785411784 litres (exact)

SourceExact by definition: 1 US gallon = 231 in³ and 1 inch = 2.54 cm
Cross-checks
  • 231 in³ × (2.54 cm/in)³ = 3,785.411784 cm³ = 3.785411784 L

m-per-foot

Verified math

1 international foot = 0.3048 m (exact)

Source1959 international yard and pound agreement; NIST SP 811, Appendix B
Cross-checks
  • Exact by definition — metric input therefore converts with no rounding error

l-per-m3

Verified math

1 m³ = 1,000 litres (exact)

SourceSI definition: 1 litre = 1 dm³ = 0.001 m³
Cross-checks
  • Exact by definition

ppm-lb-per-gallon

Industry standard

1 lb of product per 1,000 US gallons ≈ 120 ppm → divisor = 120,000 (ppm·lb⁻¹·gal). The same divisor is used for pool salt and for cyanuric acid.

SourceMass balance: 453.592 g ÷ 3,785.41 L = 119.83 ppm. Cross-checked against the Hayward Salt & Swim manual (092463 Rev C, p.11–12): salt table 10,000 gal 0→3,200 ppm = 267 lb; stabiliser table 10,000 gal 0→80 ppm = 6.7 lb.
Cross-checks
  • Mass balance: 1 lb / 1,000 US gal = 119.83 ppm
  • Hayward 092463 Rev C p.11 salt table: 10,000 gal, 0 → 3,200 ppm = 267 lb (we compute 266.67)
  • Hayward 092463 Rev C p.12 stabiliser table: 10,000 gal, 0 → 80 ppm = 6.7 lb (we compute 6.67)

salt-target-range

Industry standard

Salt-water pool target salinity 2,700–3,400 ppm (3,200 ppm optimal)

SourceHayward salt-chlorinator manuals: "the operating salt level is between 2700-3400 PPM with 3200 PPM being optimal" (092764 Rev B; 092463 Rev C p.11 marks 2,800–3,200 ppm as Ideal and 2,400–3,400 as OK)
Cross-checks
  • Hayward manual quoted above
  • Pentair IntelliChlor targets 3,600 ppm instead, so the calculator keeps saying the equipment manual wins

salt-bag-sizes

Industry standard

Standard retail pool-salt bag sizes: 40 lb and 50 lb

SourcePool-salt retail listings (Lowe's, Walmart, Amazon: 40 lb is the dominant pool-salt pack size; 50 lb also stocked)
Cross-checks
  • Used only to turn a computed dose into a purchase quantity

cya-target

Industry standard

Outdoor non-salt pool target CYA ≈ 30–50 ppm (default 40); salt-water pools commonly 60–80 ppm

SourceCommon pool-industry practice; CDC recommends not using CYA in hot tubs
Cross-checks
  • CDC: with cyanuric acid, keep free chlorine ≥ 2 ppm, pH 7.0–7.8 (cdc.gov/healthy-swimming)
Open itemAlign target range with the FC/CYA standard we adopt (see fc-cya-table).

cya-irreversible

Industry standard

Cyanuric acid is not removed by normal filtration or backwashing in practice; the practical way to lower it is draining/replacing water

SourcePool-industry practice
Cross-checks
  • Widely stated in pool chemistry references; presented as a factual caveat, not dosing guidance
Open itemConfirm with a credentialed reviewer.

fc-cya-table

Awaiting credentialed review

FC targets derived from the cyanuric-acid ratio methodology (minimum ≈ 7.5% of CYA; shock ≈ 40% of CYA)

SourceTroubleFreePool methodology (as implemented by the open-source pypoolchem library, MIT)
Cross-checks
  • TFP further-reading wiki: "Min FC" is 7.5% of the CYA level; SLAM/shock level is 40%
  • CDC floor (≥ 2 ppm FC when CYA is used) must always be shown alongside
Open itemMust be reviewed and signed off before these values are published as our guidance. We present two standards (TFP vs CDC/APSP) side by side.

lsi-structure

Industry standard

LSI = pH + TF + CF + AF − 12.1, where CF = log10(calcium hardness as CaCO₃, ppm) − 0.4 and AF = log10(carbonate alkalinity as CaCO₃, ppm)

SourceLangelier Saturation Index (Langelier, 1936); pool-specific table form documented by Service Industry News and Poolspanews
Cross-checks
  • Formula structure confirmed against Service Industry News 'Keep pool water balanced using LSI'
  • Constant 12.1 and the temperature-factor table cross-checked against the open-source pypoolchem implementation
  • CF − 0.4 cross-checked against the CPO/Taylor hardness-factor table: CH 200 → 1.90, CH 300 → 2.08, CH 800 → 2.50
Open itemConfirm temperature-factor table point-by-point against the CPO/K-2006 teaching table.

lsi-temperature-factors

Industry standard

TF lookup: 32°F→0.0, 37→0.1, 46→0.2, 53→0.3, 60→0.4, 66→0.5, 76→0.6, 84→0.7, 94→0.8, 105→0.9 (linear interpolation)

SourceOrenda-style LSI temperature factor table, as implemented by pypoolchem (MIT)
Cross-checks
  • Cross-checked against pypoolchem constants files
Open itemPoint-by-point comparison against a CPO or Taylor K-2006 printed table.

lsi-cya-correction

Awaiting credentialed review

Carbonate alkalinity = TA − (0.38772 × CYA)/(1 + 10^(6.83 − pH)) − (4.63 × borate)/(1 + 10^(9.11 − pH))

Sourcepypoolchem implementation, citing Wojtowicz (2001) 'The Carbonate System in Swimming Pool Water'
Cross-checks
  • 0.38772 = 50.04/129.07 (CYA expressed as CaCO₃); 4.63 = 50.04/10.81 (boron expressed as CaCO₃)
  • Worked example, TA 80 / CYA 50 / pH 7.5: 80 − 19.386/1.2138 = 64.03
Open itemCredentialed review required before we publish LSI results that depend on this correction. Also confirm the borate pKa (9.11 here vs 9.24 commonly quoted at 25 °C).

What this page is not

This is a working register, not a certification. A constant marked "industry standard" means we found it in published trade material and cross-checked the algebra — it does not mean a credentialed professional has reviewed it. We label those separately, and we do not publish dosing guidance from them until they are reviewed.