Pool Chemistry Cheat Sheet for Service Techs
Target ranges, dose amounts per 10,000 gallons and a worked 18,000 gallon example, built to read on your phone at the pool.
Keep this open on your phone at the pool. The ranges are commonly used residential targets in the style of ANSI/PHTA guidance. Local code may differ, especially for commercial, HOA and public pools, so check with your health department.
Target ranges
| Test | Target | Notes |
|---|---|---|
| Free chlorine (FC) | 1 to 4 ppm | With CYA, keep FC about 7.5% of CYA or more |
| pH | 7.2 to 7.8 | 7.4 to 7.6 is ideal |
| Total alkalinity (TA) | 60 to 120 ppm | 80 to 120 is common for plaster pools that use trichlor |
| Calcium hardness (CH) | 200 to 400 ppm plaster | 150 to 250 ppm for vinyl and fiberglass |
| Cyanuric acid (CYA) | 30 to 50 ppm | 60 to 80 ppm for salt chlorine generators |
| Combined chlorine (CC) | Under 0.2 ppm | This is the goal |
| Salt | 2700 to 3400 ppm | Follow the cell maker |
Minimum free chlorine for your CYA
The 1 to 4 ppm range only tells half the story once CYA is in the water. Cyanuric acid slows chlorine down, so the FC you carry has to rise with it.
| CYA | FC minimum (7.5% of CYA) |
|---|---|
| 30 ppm | 2.3 ppm |
| 40 ppm | 3.0 ppm |
| 50 ppm | 3.8 ppm |
| 60 ppm | 4.5 ppm |
| 70 ppm | 5.3 ppm |
| 80 ppm | 6.0 ppm |
Above about CYA 53, the 7.5% rule asks for more than 4 ppm. Follow the CYA rule.
Doses per 10,000 gallons
These amounts are approximate. Always test and follow the label.
| To do this | Add this |
|---|---|
| Raise FC 1 ppm | 10.2 fl oz of 12.5% liquid chlorine, or 2 oz by weight of 65% cal hypo |
| Lower TA 10 ppm | About 26 fl oz of 31.45% muriatic acid |
| Lower pH about 0.2 from around 7.8 | About 12 to 16 fl oz of 31.45% muriatic acid, depending on alkalinity |
| Raise TA 10 ppm | 1.4 lb sodium bicarbonate |
| Raise pH about 0.2 | About 6 oz soda ash, which also raises alkalinity |
| Raise CH 10 ppm | About 1.2 lb of 77% calcium chloride |
| Raise CYA 10 ppm | About 13 oz cyanuric acid |
Also worth knowing:
- 1 lb of 65% cal hypo raises FC about 7.8 ppm.
- Trichlor adds about 6 ppm CYA for every 10 ppm FC it adds. Dichlor adds about 9 ppm.
- Only dilution lowers CYA in practice.
Scale the dose to the pool
Multiply any dose by gallons divided by 10,000. A 15,000 gallon pool takes 1.5 times the table. If you do not know the volume, use the pool volume tool or these formulas:
- Rectangle: length x width x average depth x 7.5
- Round: diameter x diameter x depth x 5.9
- Oval: length x width x depth x 5.9
- Kidney: 0.45 x (A + B) x length x depth x 7.5, which is an estimate
Worked example, 18,000 gallons
Readings on a plaster pool: FC 1 ppm, CYA 40, pH 7.8, TA 90, CH 280. The multiplier is 18,000 / 10,000 = 1.8.
- FC: 7.5% of 40 is 3 ppm, so you need 2 ppm more. 10.2 fl oz x 2 x 1.8 = about 37 fl oz of 12.5% liquid chlorine.
- pH: aim for 7.6, a drop of 0.2. 12 to 16 fl oz x 1.8 = about 22 to 29 fl oz of 31.45% muriatic acid. TA sits mid-range, so start near 22 fl oz and retest.
- TA at 90 and CH at 280 are in range. Leave them alone.
Add the acid and the chlorine separately with the pump running, and let the water circulate between products.
Order of work
- Test before you add anything.
- Fix total alkalinity first, because it controls how pH behaves.
- Fix pH.
- Set free chlorine for the CYA level.
- Retest after circulation and log the numbers.
- Check CH and CYA at a set interval for each account, since both move slowly.
Mistakes that cause callbacks
- Guessing gallons. A 20 percent volume error is a 20 percent dose error.
- Chasing pH without looking at TA.
- Reading FC against 1 to 4 ppm and ignoring CYA.
- Pouring the whole dose at once when the reading is far from target. Dose in stages.
- Running stale reagents. Check expiration dates and replace on schedule.
Safety
Follow the product label and SDS. Never mix chemicals, including in a bucket. Add chemical to water, never water to chemical. Wear gloves and eye protection.
For the details behind each row, see how much muriatic acid to lower pH, chlorine types compared and saturation index explained.
Common questions
What should free chlorine be when the pool has CYA?
Hold FC at about 7.5% of CYA or more. At CYA 40 that is 3 ppm. The general residential range is 1 to 4 ppm, and higher CYA pushes the working minimum above it.
In what order should I adjust pool chemistry?
Test everything first, then fix total alkalinity, then pH, then sanitizer. Add each product separately with the pump running, and retest after the water has circulated.
Do these ranges apply to commercial pools?
They are common residential ranges in the style of ANSI/PHTA guidance. Commercial and public pools follow state and local health codes, which may differ, so check yours.