One day your pool is crystal clear. Then a monsoon storm rolls through, and by the next afternoon the water is cloudy, dull, or flat-out green. If that sounds familiar, you are not alone. Monsoon season in Arizona runs from mid-June through September, and it is one of the hardest stretches of the year on backyard pools.
Here is why storms cause algae so quickly, and what to do when it happens.
Why Pools Turn Green After a Storm
1. Dust and debris use up your chlorine
Monsoon winds carry dust, leaves, pollen, and dirt straight into the water. All of that organic material reacts with chlorine, and your sanitizer gets used up fighting debris instead of keeping algae in check. Once chlorine drops low, algae has an open door.
2. Rain dilutes and unbalances the water
A heavy downpour adds a lot of fresh water to the pool in a short time. That dilutes chlorine and can shift pH and alkalinity out of range. Unbalanced water makes chlorine less effective, even when some is still present.
3. Runoff brings in algae food
Water running off decks, landscaping, and rooftops can carry fertilizer, soil, and phosphates into the pool. These act like food for algae and help it spread faster.
4. Warm water speeds everything up
Arizona pool water is often well into the 80s or higher during monsoon season. Algae grows fastest in warm water, which is why a pool can go from clear to green in as little as a day or two after a storm.
5. Clogged baskets slow circulation
Storm debris fills skimmer and pump baskets quickly. When those baskets clog, water stops moving through the filter properly, and stagnant water gives algae a chance to settle in. Power outages that reset timers or shut off the pump make this worse.
What to Do After a Monsoon Storm
- Wait until the storm has fully passed. Stay out of the pool and away from equipment while there is lightning in the area.
- Remove debris. Skim the surface, and use a leaf net to pull out anything sitting on the bottom.
- Empty the skimmer and pump baskets. This restores flow so your filter can do its job.
- Check the water level. If heavy rain pushed the level above the middle of the skimmer opening, lower it so the skimmer works properly.
- Check your equipment. Make sure the pump is running and timers or automation settings did not reset during an outage.
- Brush the walls, steps, and floor. Brushing breaks up algae before it can take hold.
- Test and balance the water. Check chlorine, pH, and alkalinity, and adjust as needed.
- Shock the pool. A shock treatment helps restore chlorine levels and kill algae. Always follow the label, and never mix pool chemicals together.
- Run the pump longer. Keep water circulating until it clears, and clean or backwash the filter once it has caught the storm debris.
How to Stay Ahead of Monsoon Season
The best defense against a green pool is keeping chlorine and water balance steady before a storm hits, so the pool has a buffer when debris and rain arrive. Regular cleaning, emptied baskets, and a clean filter make a big difference during the summer months.
That is exactly what consistent weekly service is designed to handle. If you would rather spend monsoon season enjoying your pool instead of fighting algae, our team can help with Scottsdale pool maintenance and weekly pool service. And if your pool needs a full reset after a bad algae bloom, an acid wash and drain may be the next step.
Pool turned green after the last storm? Contact Honest Pool Care and we will get your water back to clear.