Water-Chemistry Targets and Decision Bands

This is a decision reference, not a dosing chart.

No single row can determine whether a pool or spa is safe, balanced, or ready. The correct band depends on the pool or spa, sanitizer, cyanuric acid, surface, temperature, heater, salt cell, cover, source water, equipment manuals, chemical labels, treatment history, use, and test reliability.

The values labeled approved planning aim are Version 1.0 planning bands for building property plans. They do not replace a controlling label, manual, startup instruction, warranty, law, or named technical review.

Thirty-second field reference

Sources: CDC residential treatment and testing, CDC hot-tub guidance, and the exact installed-system manuals.

How to use the bands

Public-health baseline

This is a minimum or limit from an authoritative health source. Falling outside it is not a routine optimization issue. Restrict use as appropriate, correct through an approved procedure, and verify the actual result.

Meeting a minimum does not prove that the water will remain controlled until the next service. Periodic service needs margin for sunlight, heat, users, debris, sanitizer production, and demand.

Approved planning aim

This is the intended operating area for a defined property and system. It should provide stable control between visits without violating health, label, equipment, surface, startup, or warranty constraints.

A planning aim is not universal. The property record should say which aim applies and why.

Diagnostic band

Some values are evidence rather than direct pass/fail criteria. Salt, TDS, phosphates, metals, nitrates, ORP, combined chlorine, and saturation can explain behavior, but the result must be interpreted with the system and method.

Stop or escalation condition

This is a state in which the technician cannot safely solve the problem with a routine dose or cannot prove the result. Stop, control access, preserve evidence, and escalate through the correct workflow.

Disinfectant decision bands

Free chlorine in a pool without CYA

CDC recommends at least 1 ppm free chlorine in a residential pool that does not use CYA.

• Below 1 ppm: below the CDC floor. Restrict use, confirm the test and pH, investigate demand and production, correct under the exact product and system limits, and retest.
• At or above 1 ppm: clears the CDC floor only. Compare with the approved property target, expected loss before the next visit, recent use, contamination, temperature, cover, and manufacturer maximum.
• Unexpectedly high: do not guess from color or odor. Confirm the test range and interference, product history, feeder or salt-cell output, and label-defined use restriction.

An approved planning aim for a typical residential chlorine pool without CYA is commonly 2–4 ppm, but the approved property plan and exact product or equipment limit must control.

Free chlorine in a pool with CYA

CDC recommends at least 2 ppm free chlorine when CYA or stabilized chlorine is used. CDC also notes that CYA slows disinfection.

• Below 2 ppm: below the CDC stabilized-pool floor.
• At or above 2 ppm: not automatically sufficient for every CYA concentration, demand, use pattern, or interval between visits.
• CYA unknown: the chlorine decision is incomplete. Test with a valid method or preserve the restriction.
• CYA materially above the approved property band: do not keep raising chlorine or adding stabilized product without an approved CYA-reduction and sanitizer plan.

Your company uses CYA-aware judgment. This Version 1.0 entry intentionally does not publish a single FC-to-CYA multiplier as a universal rule because available models, products, equipment instructions, service intervals, and public-health baselines must be reconciled. Until a future reviewed version adopts a validated lookup, never use this reference to justify reducing FC below the CDC minimum.

Hot-tub chlorine

CDC recommends at least 3 ppm free chlorine in a residential hot tub and advises against CYA or stabilized chlorine products.

• Below 3 ppm: below the CDC floor. Keep the spa out of use, confirm the test, and investigate rapid demand, heat, jets, users, biofilm, filter condition, feeder or generator output, and product history.
• 3–10 ppm: CDC's current public-facing hot-tub material identifies 3 ppm as the minimum and advises consulting the operator or owner above 10 ppm. The exact product, spa, cover, and manufacturer limits still control use.
• Above the valid test range or possible bleach-out: do not add more sanitizer. Dilute only for testing under the method instructions, use an approved higher-range method, or refer.

Bromine in a hot tub

CDC recommends 4–8 ppm bromine in hot tubs.

Identify whether the system uses tablets, a bromide reserve activated by oxidizer, a proprietary cartridge, or another labeled method. Record total bromine using the correct test. Do not calculate a chlorine product addition from a bromine reading.

Total and combined chlorine

Combined chlorine is commonly calculated as total chlorine minus free chlorine when the method supports that interpretation. It represents reacted chlorine species, not “extra backup chlorine.”

The planning aim is no persistent measurable combined chlorine under a valid test; representative Pentair guidance lists chloramines as “none.” A repeatable result, strong odor, user irritation, unusual demand, or poor air condition requires investigation.

Do not automatically “shock to ten times combined chlorine.” Breakpoint behavior depends on compounds, pH, CYA, temperature, product, demand, and measurement. Follow the approved oxidation or contamination procedure.

pH decision band

CDC recommends pH 7.0–7.8 for residential pools and hot tubs.

pH is logarithmic. Do not scale acid or base linearly from the difference between the current number and target.

CYA decision band

CYA protects chlorine from sunlight but slows disinfection. It also contributes to measured total alkalinity and may require a correction before saturation calculation.

Outdoor home pool

The approved planning band is commonly 30–50 ppm when a stabilized chlorine plan is appropriate. This aligns with representative pool-industry guidance and Pentair's current IntelliCenter recommendation of less than 50 ppm.

• Below the property band: do not add stabilizer until the sanitizer system, current product sources, sunlight exposure, cover, test uncertainty, and volume are confirmed.
• Within the property band: use the approved CYA-aware FC target and record the value.
• Above the property band: stop adding CYA-bearing products unless the approved treatment expressly requires them. Identify dichlor, trichlor, stabilized shock, source history, dilution options, water restrictions, and discharge requirements.
• Turbidity test outside range: report the limit honestly; do not invent precision.

Hot tub or spa

The approved planned CYA value is zero, consistent with CDC advice not to use CYA or stabilized chlorine in hot tubs. If CYA is detected, identify the product history and establish an approved transition plan rather than treating the spa as a stabilized pool.

Total alkalinity decision band

The common provisional pool planning band is 80–120 ppm, consistent with representative Pentair equipment guidance. An approved plan may use a different operating area based on sanitizer, CYA, borate, aeration, acid demand, source water, finish, and pH trend.

• Low TA: can reduce buffering and permit sharper pH movement. Confirm recent acid, source water, CYA correction, and test validity before adding product.
• High TA: can increase acid demand and carbon-dioxide outgassing behavior in an aerated system. Do not lower it through repeated large acid doses without a controlled pH and aeration plan.
• Spa TA: jets and blowers can drive pH upward rapidly. Use the exact spa and sanitizer plan; do not restore a generic pool number automatically every visit.
• Saturation input: record measured TA and the corrected carbonate-alkalinity value required by the selected method. Never correct twice.

TA is not a direct measure of pH, and a saturation result cannot authorize TA outside a controlling equipment, surface, or product range.

Calcium-hardness decision band

The common provisional pool planning band is 200–400 ppm, consistent with representative equipment guidance. The correct target depends strongly on the pool or spa surface and equipment.

• Cementitious plaster, pebble, quartz, exposed aggregate, and grout: protect the surface through the approved saturation and startup plan, not calcium alone.
• Vinyl, fiberglass, acrylic, and coatings: do not raise calcium merely to copy a plaster target. Check heater, grout, tile, salt cell, product, and manufacturer requirements.
• High calcium: evaluate source water, evaporation and refill, temperature, pH, TA, salt, scale, and feasible dilution or treatment. Do not chase the index with unstable low pH.
• Low calcium: confirm test and surface before addition. Calcium chloride generates substantial heat when dissolving; the exact label controls.

NPC identifies low pH, alkalinity, or calcium as potential contributors to cementitious-surface deterioration and high values as contributors to scale. The combined balance and duration matter; one measurement does not date or prove damage.

Saturation-index decision band

The approved planning aim is commonly -0.3 to +0.3 using one approved, documented method with actual pH, calcium, temperature, corrected alkalinity, CYA, salt or TDS, and any required borate input.

• Below -0.3: increased calcium-carbonate undersaturation tendency. Confirm inputs and consider cementitious surfaces and equipment; do not label all metal risk “corrosion” from LSI alone.
• -0.3 to +0.3: common planning band for calcium-carbonate equilibrium. Individual parameters still must pass.
• Above +0.3: increased scale tendency, especially at warm heater and salt-cell surfaces. Confirm tests before treatment.

Some manufacturer algorithms and acceptable bands differ, for example, the current IntelliCenter guide describes a wider satisfactory index around zero. Use the exact approved method and equipment instruction. Never compare a number from one calculator with the target band from another without confirming their inputs and corrections.

Salt, TDS, and conductivity

There is no universal salt target. Use the exact salt-cell, controller, or proprietary sanitizer manual. Representative Pentair systems span ranges that should not be copied to another manufacturer or model.

Compare:

• controller reading;
• independent salinity test;
• water temperature and compensation;
• recent salt addition, rain, overflow, refill, leak, or splash-out;
• cell condition, flow, wiring, and calibration guidance.

TDS and conductivity do not directly identify every dissolved substance or prove the water is “old.” Saltwater pools intentionally have high conductivity. Use source-water comparison, startup value, trend, individual ions, performance, and manufacturer limits before recommending water replacement.

Metals, phosphates, nitrates, and ORP

These values can be useful, but they are not universal release criteria.

• Metals: a result or stain color requires method, source, oxidation state, water balance, product, and equipment context. “None” may be a manufacturer aim, but field methods have detection limits.
• Phosphates: can support algae growth, but a phosphate result does not replace adequate sanitizer, circulation, filtration, and physical cleaning. Treat only under an approved product-specific plan.
• Nitrates: may contribute to demand and indicate source or contamination history; removal options are limited. Confirm before recommending dilution.
• ORP: depends on sanitizer, pH, CYA, temperature, electrode condition, flow, and system design. A controller setpoint is not a direct substitute for a manual disinfectant test.

Do not add specialty treatment because a sales-oriented test flags one number without confirming the cause, benefit, side effects, and property objective.

Results that override the table

Keep the pool or spa out of use or escalate when any of these applies:

• water is cloudy enough to obscure drains, fittings, steps, or the floor;
• disinfectant is below the applicable CDC floor and cannot be corrected and verified;
• pH is outside 7.0–7.8 and cannot be corrected and verified;
• a hot tub exceeds 104°F;
• there is fecal material, vomit, blood, dead animal, suspected illness event, slime, biofilm, unknown chemical, or other contamination;
• a suction fitting, electrical component, heater, pool or spa structure, cover, or barrier is unsafe;
• a test may be invalid or bleached out;
• the chemical or product history is unknown enough that additions could mix incompatibly;
• required treatment, draining, discharge, repair, or diagnosis is outside authorization.

Chemistry ranges do not override physical safety.

Dosing boundary

Never calculate an addition from this page alone. A valid dose requires:

1. confirmed current result and method;
2. verified pool or spa volume;
3. exact target tied to the correct source;
4. exact product and concentration;
5. product-label dosage and PPE;
6. predicted side effects on pH, TA, calcium, CYA, salt, temperature, or saturation;
7. compatible circulation and application point;
8. separation from other products;
9. use restriction and retest time;
10. documented actual amount and measured result.

Use Calculating and Adding Pool Chemicals for the complete procedure.