Pool chemistry cheat sheet: every number you need
One page. Every target range, every chemical, every quick fix. Bookmark this page — it's the only reference you need poolside.
The master reference table
These are the numbers that keep your pool water balanced, safe, and clear. If you only memorize one table, make it this one.
| Parameter | Ideal Range | Too Low | Too High | Test Frequency |
|---|---|---|---|---|
| Free Chlorine (FC) | 2 – 4 ppm (varies w/ CYA) | Algae, bacteria risk | Skin/eye irritation | 2 – 3x/week |
| Combined Chlorine (CC) | < 0.5 ppm | N/A | Chloramines, shock needed | Weekly |
| pH | 7.4 – 7.6 | Corrosion, eye sting | Scale, weak chlorine | 2 – 3x/week |
| Total Alkalinity (TA) | 80 – 120 ppm | pH bounces | pH hard to lower | Weekly |
| Calcium Hardness (CH) | 200 – 400 ppm | Corrosion, etching | Scale, cloudy water | Monthly |
| CYA (Stabilizer) | 30 – 50 ppm | Chlorine burns off fast | Chlorine becomes ineffective | Monthly |
| Water Temperature | N/A | N/A | Affects LSI, chlorine demand | With each test |
| Salt (SWG only) | 2700 – 3400 ppm | Low output | Cell damage | Monthly |
| LSI | -0.3 to +0.3 | Corrosive water | Scale-forming water | With each test |
Quick fix reference
When a reading is off, here's what to add and roughly how much. All doses are per 10,000 gallons. Always retest after circulating for at least 30 minutes.
| Problem | Chemical | Dose Guideline |
|---|---|---|
| FC too low | Liquid chlorine | ~10 oz per 1 ppm |
| pH too low | Soda ash | ~6 oz per 0.2 pH |
| pH too high | Muriatic acid | ~3 oz per 0.2 pH |
| TA too low | Baking soda | ~1.5 lbs per 10 ppm |
| TA too high | Muriatic acid | ~12 oz per 10 ppm |
| CH too low | Calcium chloride | ~1.25 lbs per 10 ppm |
| CYA too low | Stabilizer | ~13 oz per 10 ppm |
| CYA too high | Partial drain/refill | No chemical fix |
All doses are per 10,000 gallons
These are starting-point guidelines, not exact prescriptions. Pool volume, current levels, and chemical concentration all affect the actual dose. Always retest after adding chemicals and adjust from there.
The adjustment order
When multiple readings are off, don't fix them all at once. Follow this order — each step affects the ones after it:
- Total Alkalinity — TA buffers pH. If TA is wrong, pH won't hold no matter what you do.
- pH — Once TA is stable, pH adjustments will actually stick.
- Calcium Hardness — CH affects LSI and water balance, but won't shift pH or TA.
- CYA (Stabilizer) — CYA determines your chlorine target. Set it before adding chlorine.
- Chlorine — Now you know your CYA level and can add the right amount of FC.
Skipping this order is the most common reason pool owners chase numbers in circles. Fix alkalinity first, then work down the list.
FC target by CYA level
The "right" amount of free chlorine depends on how much stabilizer is in your water. Higher CYA means you need more FC to maintain effective sanitization.
| CYA (ppm) | Minimum FC (ppm) | Target FC (ppm) |
|---|---|---|
| 30 | 2 | 3 |
| 40 | 3 | 4 |
| 50 | 4 | 5 |
| 60 | 5 | 6 |
| 80 | 6 | 7 |
Why does CYA matter so much?
CYA shields chlorine from UV breakdown, but it also binds to chlorine and slows its killing power. The higher your CYA, the more FC you need to keep the same level of sanitization. A pool with FC of 3 ppm and CYA of 80 is effectively under-chlorinated — even though 3 ppm looks fine on paper.
LSI quick reference
The Langelier Saturation Index tells you whether your water wants to dissolve surfaces (corrosive) or deposit minerals (scale-forming). Here's what each range means in plain English:
| LSI Value | Status | What It Means |
|---|---|---|
| -0.6 or lower | Very corrosive | Water is aggressively dissolving plaster, metal, and grout. Fix immediately. |
| -0.3 | Slightly corrosive | Water is mildly aggressive. Raise pH, TA, or CH to bring LSI up. |
| 0 | Perfectly balanced | Water is in equilibrium — not attacking surfaces and not forming scale. |
| +0.3 | Slightly scale-forming | Water may deposit light scale over time. Lower pH or TA slightly. |
| +0.6 or higher | Very scale-forming | Heavy scale buildup on surfaces, equipment, and plumbing. Fix immediately. |
Your target is an LSI between -0.3 and +0.3. Zero is perfect, but anywhere in that range is safe for your pool surfaces and equipment.
Testing schedule summary
Not everything needs daily testing. Here's a realistic schedule that keeps your pool safe without wasting time or test strips.
| Frequency | What to Test |
|---|---|
| 2 – 3x per week | Free Chlorine, pH |
| Weekly | Combined Chlorine, Total Alkalinity |
| Monthly | Calcium Hardness, CYA, Salt (if SWG) |
| With each test | Water Temperature (for LSI calculation) |
During heavy use, after storms, or after adding chemicals, test FC and pH more frequently. When in doubt, test.
Skip the cheat sheet — let the app do it
PoolChem Tracker calculates every target, every dose, and every adjustment automatically. Just enter your readings and get instant recommendations.
Keep reading
- Pool Chemistry for Beginners: The 5 Numbers That Matter — start here if you're new to pool care
- How to Balance Pool Water in 4 Steps — a step-by-step walkthrough of the adjustment process
- Pool Chlorine Levels Chart: What Your Readings Mean — a deep dive into FC, TC, and CC readings
- What Is LSI and Why Does Your Pool Need It? — understand the saturation index in detail