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.

Status	Count	Meaning
Verified math	1	Deterministic math or unit conversion. Provable in one line.
Industry standard	6	Published industry formula. Presented with its source, not as our own advice.
Awaiting credentialed review	2	Not 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

Source	Standard 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…

`ppm-lb-per-gallon`

Industry standard

1 lb of salt per 1,000 gallons of water raises salinity ≈ 120 ppm → divisor = 120,000 (ppm·lb⁻¹·gal)

Source	Industry dosing convention (1 lb salt / 1,000 gal ≈ 120 ppm). Rearranged: lb = Δppm × gallons / 120,000
Cross-checks	Common measurement cited in pool trade material Informational only — not yet validated against a specific product label (see todo)
Open item	Validate against one manufacturer label (e.g. a pool-salt bag: '1 lb per 1,000 gal raises 120 ppm') or a CPO/SI teaching chart before publishing guidance.

`salt-target-range`

Industry standard

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

Source	Salt chlorinator manufacturer guidance range
Cross-checks	Range presented as guidance with the calculator, not as our own recommendation
Open item	Confirm range against at least one major salt-cell manufacturer manual before publishing guidance.

`cya-target`

Industry standard

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

Source	Common 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 item	Align 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

Source	Pool-industry practice
Cross-checks	Widely stated in pool chemistry references; presented as a factual caveat, not dosing guidance
Open item	Confirm 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)

Source	TroubleFreePool methodology (as implemented by the open-source pypoolchem library, MIT)
Cross-checks	Implementation cross-checked against pypoolchem constants (derived from the TFP PoolMath calculator, validated against the Orenda LSI calculator) CDC floor (≥ 2 ppm FC when CYA is used) must always be shown alongside
Open item	Must 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 ppm), AF = log10(carbonate alkalinity ppm)

Source	Langelier Saturation Index (Langelier, 1936); pool-specific 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 temperature-factor table cross-checked against the open-source pypoolchem implementation
Open item	Confirm 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)

Source	Orenda-style LSI temperature factor table, as implemented by pypoolchem (MIT)
Cross-checks	Cross-checked against pypoolchem constants files
Open item	Point-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))

Source	pypoolchem implementation, citing Wojtowicz (2001) 'The Carbonate System in Swimming Pool Water'
Cross-checks	Worked example from the library: TA 80, CYA 50, pH 7.5 → 73.77
Open item	Credentialed review required before we publish LSI results that depend on this correction.

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.