A major storm — defined as 2+ inches of rain, significant wind, or flooding conditions — is not a rain shower. It's a pool chemistry reset event that requires a systematic response, not just a quick shock and hope. This protocol covers the full recovery sequence from storm end to confirmed clear water.
Before starting any treatment, assess what the storm actually did to the pool:
The severity of the chemistry disruption depends on:
This is the step that gets skipped in a hurry, and it determines how much chemistry you'll use. Every piece of organic material in the pool consumes chlorine. Treating before removing debris means your shock is fighting decomposing leaves instead of sanitizing water.
Full test kit, not strips. After a major storm, you need accurate readings on every parameter:
| Parameter | Expected Post-Storm Direction | Target |
|---|---|---|
| Free Chlorine | Down (diluted + consumed by debris) | Per CYA level minimum |
| pH | Down (acidic rain) | 7.4–7.6 |
| Total Alkalinity | Down (dilution + acid rain) | 80–120 ppm |
| Calcium Hardness | Down (dilution) | 200–400 ppm |
| CYA | Down (dilution) | 30–50 ppm |
| Combined Chlorine | Up (increased demand) | <0.2 ppm |
| Phosphates | Up (runoff) | <100 ppb |
| Salt (SWG) | Down (dilution) | Per controller spec |
The order matters. Do not shortcut the sequence:
If TA is below 80 ppm, add sodium bicarbonate to bring it to 100 ppm before adjusting pH. Low TA means pH adjustments won't hold — fix the buffer first. Add 1.5 lbs per 10,000 gallons to raise TA 10 ppm. Circulate 2 hours before retesting.
Lower the target to 7.2 instead of the normal 7.4 before shocking — the lower pH maximizes chlorine activity during the shock treatment. Add muriatic acid; retest after 30 minutes.
After TA and pH are in range:
Add at dusk. Run pump continuously overnight and through the next day.
If combined chlorine is above 0.5 ppm after the storm, use breakpoint chlorination rather than standard shock dose. Breakpoint requires bringing FC to 10× the combined chlorine reading. A CC of 1.0 ppm means you need to reach FC of 10+ ppm. This is more product than standard shock, but it's the only way to break down chloramines chemically.
If CH dropped below 175 ppm from dilution, add calcium chloride. This step can wait until after shock has taken effect and chemistry is stabilizing.
48 hours after initial shock, test phosphates. If above 500 ppb (particularly likely after landscaping runoff entered the pool), add a phosphate remover before phosphates can fuel an algae bloom. This step is easily forgotten but important in storm recovery.
If CYA has dropped below 30 ppm from dilution, add to the skimmer while the pump is running. Wait 48–72 hours before retesting CYA.
Run the pump continuously for 48 hours after major shock treatment. Backwash or rinse the cartridge every 12 hours during this period — storm debris plus dead algae (if any) will load the filter rapidly. Log each backwash and filter rinse in SplashLens to track the recovery timeline.
Log pre-storm baseline, post-storm assessment readings, and day-by-day chemistry during recovery. Build a storm response record that demonstrates professional management — and shows the homeowner exactly what the storm did and what it took to fix it.
Open SplashLens Free →Before touching the water chemistry, remove all physical debris. Skim the surface, empty skimmer and pump baskets, and vacuum the pool floor. Debris that's not removed before chemical treatment consumes the chemicals you add. Physical debris removal must happen before any chemistry testing or addition.
Major storms introduce acidic rainwater (drops pH and alkalinity), runoff with fertilizers and pesticides (spikes phosphates and chlorine demand), dilution of all dissolved chemicals, and atmospheric contamination. The combined effect requires full chemistry testing and correction of every parameter.
For a major storm with significant rainfall and debris: 3–5 days from storm end to clear, safe pool. Day 1: debris removal and chemistry correction. Days 2–3: continuous filtration clears dead algae and particulate. Days 4–5: verify chemistry has stabilized.
Before, if you have advance warning. Lowering the pool 2–4 inches before a predicted 2+ inch rain event prevents overflow and reduces dilution. After the storm, drain to operating level before beginning chemistry assessment and treatment.