How to Prevent Algae Growth After a Rainstorm

Rain might feel refreshing, but for your pool, it can cause big trouble. The extra water dilutes your chemicals, and wind can carry in leaves, dirt, and even algae spores. If you don’t act quickly, algae can take over fast. Here’s how to protect your pool after a storm.

Why Rain Affects Your Pool

Rainwater is usually acidic and contains contaminants that disrupt your water balance. Storm runoff and debris introduce phosphates, which algae love to feed on. The sudden change in pH and chlorine levels creates a perfect opportunity for algae to grow.

Signs That Algae Is About to Bloom

Don’t wait for green water to act. Here are early signs that algae might be starting:

• Cloudy or dull water

• Slight green tint along the walls

• Slippery or slimy pool surfaces

• Low chlorine levels despite recent treatment

What to Do Right After a Rainstorm

The best way to fight algae is to take immediate action after the rain stops. Don’t let the water sit untreated.

1. Remove Debris Immediately

Use a skimmer net to clear out leaves, branches, and dirt. Organic material feeds algae and clogs up your filtration system.

2. Brush and Vacuum the Pool

Brush the walls and floor to loosen any potential algae spores. Then vacuum thoroughly to get rid of hidden debris and contaminants.

3. Test the Water Chemistry

Use test strips or a test kit to check pH, chlorine, alkalinity, and stabilizer levels. Rain often dilutes chlorine and lowers pH.

4. Adjust and Rebalance the Water

Bring your pH and alkalinity back into range before shocking. This makes the chlorine work more effectively. Add the necessary balancers.

5. Shock the Pool

A strong chlorine shock kills algae before it becomes a full bloom. Follow the product instructions and keep the pump running for at least 24 hours.

6. Clean or Backwash the Filter

Storm debris can clog up your filter quickly. Clean the cartridge, backwash a sand filter, or rinse a DE filter to keep circulation strong.

Ongoing Prevention Tips

Don’t let your guard down after one treatment. Stay ahead of future storms with good pool habits.

Keep Chemicals Balanced

Maintain your sanitizer, pH, and alkalinity levels. Consistent water chemistry is your first line of defense against algae.

Use Algaecide as a Preventative

You don’t have to wait for algae to show up. A weekly dose of algaecide can stop spores from growing in the first place.

Trim Back Trees and Plants

Prevent organic debris from falling into your pool by keeping nearby plants trimmed. Less debris means fewer nutrients for algae.

Cover the Pool During Heavy Rain

If possible, use a pool cover before a storm. It helps keep out dirt and maintains chemical balance.

Stay in Control After the Storm

Rain doesn’t have to ruin your pool. With quick action and a little prep, you can keep algae out and your water safe. Follow these steps every time it rains to avoid the stress and cost of a green pool.