Ideal pool chemistry levels chart
Every test result on your strip or drop kit has a range it should sit in. This chart puts the official numbers from the CDC and the Model Aquatic Health Code next to the targets home pool owners commonly use, and says where each one comes from. Hot tubs have their own table further down, and the last table scales chlorine to your stabilizer level.
Pool chemistry levels at a glance
| Test | Official (CDC / MAHC) | Common home target |
|---|---|---|
| Free chlorine, no stabilizer | At least 1 ppm | 1–3 ppm |
| Free chlorine, with CYA | At least 2 ppm | 7.5% of CYA (3 ppm at 40) |
| Combined chlorine | Act above 0.4 ppm | As near 0 as you can read |
| pH | 7.0–7.8 | 7.4–7.6 |
| Total alkalinity | 60–180 ppm | About 70–120 ppm |
| Calcium hardness | Up to 2,500 ppm | Saturation index near 0 |
| CYA (stabilizer) | Up to 90 ppm | 30–50 ppm; salt pools 60–80 |
| Salt | None set | Your cell’s manual (e.g. 3,200) |
| Bromine | 3–8 ppm (spas 4–8) | 3–6 ppm |
| Saturation index | Check monthly | −0.3 to +0.5 |
| Temperature | Hot tubs ≤ 104°F (40°C) | 78–82°F for pools |
Notes on the table
- Free chlorine. The CDC and MAHC floor is 1 ppm without stabilizer and 2 ppm with it; the maximum is the product label, and above 10 ppm is an imminent hazard in public pools (MAHC). Outdoors without CYA, sunlight burns chlorine off fast.
- Chlorine with CYA. The 7.5%-of-CYA target is the Trouble Free Pool hobbyist convention (see the FC-by-CYA table below). The MAHC treats a CYA-to-chlorine ratio above 45:1 as an imminent hazard.
- Combined chlorine = total chlorine − free chlorine. A rising number means used-up chlorine is building; the MAHC asks public pools to act above 0.4 ppm.
- pH. 7.4–7.6 is the middle of the CDC’s 7.0–7.8 range; the CDC notes pH above 8 cuts chlorine’s effectiveness. Below 6.5 or above 8.0 is an imminent hazard in public pools (MAHC).
- Alkalinity. 70–120 ppm is a common home range inside the MAHC’s 60–180. With CYA in the water, the MAHC annex corrects TA by subtracting CYA ÷ 3.
- Calcium. There is no official minimum. Plaster and spa makers publish their own ranges; the saturation index calculator shows whether yours balances.
- Stabilizer. 30–50 ppm (chlorine added by hand) and 60–80 ppm (salt pools) are common practice for outdoor pools; indoor pools need little or none. 300 ppm or more closes a public pool (MAHC).
- Salt. Follow your cell’s manual: Hayward AquaRite 2,700–3,400 ppm, 3,200 optimal; Pentair IntelliChlor 2,600–4,500 ppm, 3,600 ideal.
- Bromine. MAHC: 3.0–8.0 ppm in pools and 4.0–8.0 in spas, above 8 an imminent hazard. The 3–6 ppm home target is from a brominating-tablet label (SpaGuard).
- Saturation index. Taylor Technologies treats −0.3 to +0.5 as balanced and says within ±0.5 needs no adjustment.
- Temperature. The US DOE Energy Saver puts the usual pool range at 78–82°F, with each degree warmer costing 10–30% more energy. The CDC sets 104°F (40°C) as the hot tub maximum.
Two things trip people up when they read the official column. First, the MAHC is a model code for public pools: it sets floors and hazard limits, not comfortable targets, and your state or county code may differ. Second, most of the limits interact. Chlorine only works at the strength you think if pH is in range, and stabilizer changes how much chlorine you need, so look at the whole row set, not one number.
Hot tub chemistry levels
Hot water, small volume and several people at once mean a hot tub uses up sanitizer far faster than a pool. The official numbers are higher, and stabilizer is out.
| Test | Official (CDC / MAHC) | Common home target / label |
|---|---|---|
| Free chlorine | At least 3 ppm | Test before every soak |
| Bromine | 4–8 ppm | 3–6 ppm (one tablet label) |
| pH | 7.0–7.8 | 7.4–7.6 |
| Total alkalinity | 60–180 ppm | The tub maker’s manual |
| Cyanuric acid | None (CDC) | Drain often if you use dichlor |
| Temperature | Up to 104°F (40°C) | Lower for long soaks |
| Testing | At least twice a day | Before each use |
Starting a tub from fresh water is covered step by step in how much chlorine to start a new hot tub, the bromine version in how to start a hot tub on bromine, and plain bleach in how much bleach to put in a hot tub. If the pH drifts high, see how much muriatic acid for a hot tub.
Free chlorine by stabilizer (CYA) level
Stabilizer shields chlorine from sunlight, but it also holds most of the chlorine in a slow, bound form. The more CYA in the water, the more free chlorine it takes to do the same job. The CDC and MAHC only set a floor (2 ppm with CYA, and no more than 45 ppm of CYA per 1 ppm of chlorine in public pools). Home owners mostly use the hobbyist chart from Trouble Free Pool, which scales chlorine to CYA.
| CYA | Minimum FC (7.5%) | Salt pool minimum (5%) | Shock / SLAM FC | MAHC public-pool floor |
|---|---|---|---|---|
| 0 (none) | 1 ppm (CDC minimum) | 1 ppm | 10 ppm* | 1 ppm |
| 20 ppm | 2 ppm | 1 ppm | 8 ppm | 2 ppm |
| 30 ppm | 2 ppm | 1.5 ppm | 12 ppm | 2 ppm |
| 40 ppm | 3 ppm | 2 ppm | 16 ppm | 2 ppm |
| 50 ppm | 4 ppm | 2.5 ppm | 20 ppm | 2 ppm |
| 60 ppm | 5 ppm | 3 ppm | 24 ppm | 2 ppm |
| 70 ppm | 5 ppm | 3.5 ppm | 28 ppm | 2 ppm |
| 80 ppm | 6 ppm | 4 ppm | 32 ppm | 2 ppm |
| 90 ppm | 7 ppm | 4.5 ppm | 36 ppm | 2 ppm |
| 100 ppm | 8 ppm | 5 ppm | 40 ppm | 2.2 ppm |
Read across from your CYA test. At 40 ppm, for example, keep free chlorine at 3 ppm or more by the hobbyist convention, and raise it to 16 ppm to clear algae. For your exact number, use the chlorine and CYA calculator; for a salt pool, what CYA and chlorine a salt water pool needs walks through the lower 5% figure.
How to get each number into range
- Stabilizer too low. Add granular cyanuric acid: how much stabilizer for a 10,000 gallon pool and how much stabilizer for a 20,000 gallon pool have the doses. Too high? Only fresh water lowers it — see how much water to drain to lower CYA.
- Salt too low. Salt only leaves with water, so add it once and top up: how much salt for a 10,000 gallon pool, how much salt for a 15,000 gallon pool and how much salt for a 20,000 gallon pool.
- pH or alkalinity too high. Use acid: how much muriatic acid to lower pH in 10,000 gallons and how much muriatic acid to lower alkalinity.
- pH too low. Soda ash: how much soda ash to raise pH. Alkalinity too low: baking soda, as in how much baking soda to raise alkalinity.
- Calcium too low. Calcium chloride: how much calcium chloride to add to a pool. Then check the result with the saturation index calculator.
Order matters when several numbers are off. A common sequence is alkalinity first (it buffers pH), then pH, then calcium, then chlorine, with time to circulate and a retest between each. The pool chemical dose chart has the amounts per 10,000 gallons for every product here.
Frequently asked questions
Are the CDC pool chemistry levels the same as the home targets?
No. The CDC and Model Aquatic Health Code set minimums and hazard limits, mainly for public pools. Home targets such as 7.4–7.6 pH or chlorine scaled to stabilizer sit inside those limits with a margin.
What is the most important pool chemistry level to get right?
Free chlorine, followed closely by pH. Chlorine does the sanitizing, and pH decides how well it works; the CDC notes that pH above 8 makes chlorine much less effective.
Should a hot tub have the same chemistry as a pool?
Not quite. The CDC asks for at least 3 ppm chlorine (or 4–8 ppm bromine) in hot tubs, no cyanuric acid, and water no hotter than 104°F. pH and alkalinity ranges are the same.
Sources
- CDC Healthy Swimming — Home pool and hot tub water treatment and testing (opens in a new tab) — pH 7.0–7.8; free chlorine at least 1 ppm in pools (2 ppm with cyanuric acid) and 3 ppm in hot tubs; no CYA in hot tubs; test twice a day.
- CDC Healthy Swimming — Staying healthy in hot tubs (opens in a new tab) — No hotter than 104°F (40°C); chlorine at least 3 ppm, bromine 4–8 ppm, pH 7.0–7.8; no children under 5.
- CDC Healthy Swimming — Operating public pools, hot tubs and splash pads (opens in a new tab) — Hot tubs: at least 3 ppm free chlorine or 4 ppm bromine; water no hotter than 104°F (40°C).
- CDC — Model Aquatic Health Code, 5th edition (2024), code (opens in a new tab) — Free chlorine minimum 1.0 ppm (2.0 with CYA, 3.0 in spas); pH 7.0–7.8; CYA at or below 90 ppm; CYA:FC above 45:1 is an imminent hazard; TA 60–180 ppm; turnover tables.
- CDC — Model Aquatic Health Code, 5th edition (2024), annex (opens in a new tab) — CYA reduces chlorine’s effectiveness; correcting total alkalinity for CYA by subtracting CYA ÷ 3.
- Trouble Free Pool (hobbyist forum wiki) — CYA/chlorine relationship (opens in a new tab) — A widely used hobbyist convention, not an official standard: minimum FC 7.5% of CYA, SLAM (shock) level 40% of CYA, salt-water pools 5%.
- Trouble Free Pool — The free chlorine and cyanuric acid relationship (chart) (opens in a new tab) — The forum’s printed chart of minimum and SLAM free chlorine by CYA, with a separate salt-water table.
- Taylor Technologies — Using the Taylor circular Watergram (opens in a new tab) — Saturation index = pH + temperature factor + log CH + log carbonate alkalinity − constant; within ±0.5 of zero needs no adjustment.
- Hayward — AquaRite salt chlorination owner’s manual (092538 Rev D) (opens in a new tab) — Ideal salt 2,700–3,400 ppm, 3,200 ppm optimal.
- Pentair — IntelliChlor Plus / LT owner’s manual (opens in a new tab) — Ideal salt 3,600 ppm, range 2,600–4,500 ppm.
- SpaGuard — Brominating Tabs (Leisure Time) (opens in a new tab) — BCDMH 98%; keep bromine at 3–6 ppm.
- Leisure Time — Spa 56 chlorinating granules (opens in a new tab) — 55% available chlorine; ½ oz per 500 gallons for a 2–3 ppm residual, 1 oz per 500 gallons to shock.
- US EPA label 82289-2 — sodium hypochlorite pool chlorine (opens in a new tab) — Pool re-entry prohibited above 4 ppm chlorine (spas above 5 ppm); superchlorinate at 5–10 ppm.
- US DOE Energy Saver — Managing swimming pool temperature (archived) (opens in a new tab) — Typical pool temperature 78–82°F; each degree warmer costs 10–30% more energy.
- US EPA — Introduction to pesticide labels (opens in a new tab) — Pool sanitizers are registered pesticides; the label is the law.
- CDC — Pool chemical injuries press release (2014) (opens in a new tab) — Never mix pool chemicals, especially chlorine products with acid; add chemical to water, never water to chemical.