Monsoon storms and heavy rains are a welcome break from Arizona heat, but for pool owners they bring a predictable set of headaches. Runoff, dust, organic debris, and sudden dilution of pool water can throw your chemistry out of balance and create ideal conditions for algae, cloudy water, or equipment stress. Knowing how to treat your pool after a storm lets you recover quickly and avoid costly repairs. Below is a practical, step-by-step guide for effective post-storm pool maintenance and rain pool balance.
Why Monsoons and Rain storms disrupt pool chemistry
Rainwater is not neutral. It often contains dissolved minerals, organic contaminants, and air-borne debris. Heavy rain or monsoons lowers sanitizer levels by dilution, can drop pH depending on acidity, and washes dirt and leaves into the pool that consume chlorine as they decompose. Monsoon winds also drive dust and pollen into the water. The result is increased demand on your filtration and sanitizer systems and an elevated risk of algae blooms and cloudy water.
Step 1: Wait and inspect
After the worst of the monsoon storm passes, wait until it is safe to approach the pool. Check for obvious damage to equipment, fallen branches, clogged drains, or loose pool furniture. If there is significant flooding around your equipment pad, keep power off to the pump and heater until a qualified tech confirms it is safe. Remove large debris by hand so the filter does not become overloaded.
Step 2: Test the water
Test the water as soon as possible with a reliable test kit or a test strip that measures free chlorine, pH, total alkalinity, and cyanuric acid. Because rain dilutes chemicals, you will often find low free chlorine and altered pH. Record the readings so you can track changes during the recovery process.
Step 3: Clean the pool and equipment
After the monsoon passes, skim the surface, vacuum the floor, and brush walls and tiles to dislodge organic matter. Empty skimmer and pump baskets frequently while you clean. If your filter pressure climbs quickly, backwash sand or DE filters, or rinse cartridge filters. Cleaning reduces the organic load that consumes chlorine and causes cloudiness.
Step 4: Restore sanitizer quickly
Low chlorine is the biggest post-storm risk. If free chlorine is below the recommended level, apply a shock treatment that raises chlorine to a breakpoint level. For safety and effectiveness, shock in the evening when sunlight will not rapidly degrade the chlorine. Follow product instructions for dosing based on your pool volume.
Step 5: Balance pH and alkalinity
Rainwater can push pH up or down depending on its composition. Aim for pH 7.4 to 7.6 and total alkalinity 80 to 120 ppm. If pH is too low, add sodium bicarbonate or soda ash as appropriate. If pH is too high, use muriatic acid or a pH reducer in small measured doses. Adjust alkalinity first, then fine-tune pH.
Step 6: Address calcium hardness and staining
Heavy rain and runoff can change calcium levels, especially if you top off the pool with hard water. Test calcium hardness and keep it in the 200 to 400 ppm range to avoid scaling or etching. If metals from runoff are present, use a metal sequestrant to prevent staining and discoloration.
Step 7: Use a clarifier or flocculant if necessary
If the water remains cloudy after shock and circulation, use a clarifier to help the filter capture fine particles. In severe cases, a flocculant can be used to bind particles so they settle to the bottom for vacuuming. Follow directions carefully to avoid overuse.
Step 8: Run filtration longer and monitor frequently
After a storm, increase your filtration run time to 12 to 24 hours daily until the pool clears. Check chemical levels daily for several days. Empty skimmer and pump baskets more frequently during this period to preserve flow and prevent pump strain.
Step 9: Consider phosphate control and algaecide
Storm runoff often carries phosphates that feed algae. If phosphate levels are high, add a phosphate remover according to label instructions. For caution in warm, nutrient-rich conditions, consider a preventive algaecide treatment after shocking the pool.
Step 10: Inspect and service equipment
Once chemistry is stabilized, inspect the pump, filter, heater, and electrical connections. If any equipment was submerged or exposed to mud, have a certified technician evaluate and service them before regular operation resumes.
Quick post monsoon storm checklist
- Remove debris and dry wet covers.
- Test free chlorine, pH, alkalinity, calcium hardness, and CYA.
- Shock the pool at night if chlorine is low.
- Backwash or clean filters; run filtration longer.
- Adjust pH and alkalinity as needed.
- Use clarifier or flocculant for persistent cloudiness.
- Apply phosphate remover and algaecide if warranted.
- Inspect equipment and call a professional for any flood damage.
Act quickly after a monsoon or rain to prevent minor imbalances from becoming major problems. Consistent testing and longer filtration are the two most effective defenses. With a focused post-storm routine, Arizona pool owners can restore water quality fast, protect their equipment, and keep the pool ready for use when the sun returns.