How to Treat Green Water in a Hot Tub

Green water is more than just unappealing, it often signals an imbalance or contamination. Understanding the causes helps you solve the issue quickly.

Common Causes of Green Water

• Algae Growth: Warm, stagnant water and sunlight create the perfect breeding ground.

• Low Sanitizer Levels: Without enough chlorine or bromine, bacteria and algae thrive.

• Imbalanced pH or Alkalinity: When pH and alkalinity are out of range, water can become cloudy and green.

• Debris and Organic Matter: Leaves, oils, and dirt feed algae growth.

First Steps to Take When You Notice Green Water

Assess the Situation

Before diving in with chemicals, evaluate how severe the problem is.

• Light tint of green: Likely mild algae growth.

• Dark green or slimy: Advanced algae infestation.

• Cloudy and smelly: May indicate bacterial contamination too.

Test the Water

• Use a reliable test kit to check sanitizer, pH, alkalinity, and calcium levels.

• Record the results so you can track progress.

Step-by-Step Process to Treat Green Hot Tub Water

Follow these steps to safely and effectively treat green water.

Drain or Keep the Water?

When to Drain

• Water has been green for weeks.

• You can’t balance chemistry after repeated attempts.

• Heavy debris buildup inside the tub.

When to Treat Without Draining

• Water is only mildly green.

• Chemistry was recently balanced but sanitizer dropped.

Cleaning and Treatment Process

Remove Debris First

• Skim out leaves, dirt, and other visible contaminants.

• Wipe the walls to remove slimy residue.

Adjust Alkalinity and pH

• Target alkalinity: 80–120 ppm.

• Target pH: 7.2–7.8.

• Use appropriate increasers or decreasers to reach these levels.

Shock the Water

• Use a chlorine shock for severe cases.

• Use a non-chlorine shock for lighter cases if you want to soak sooner.

Run the Jets

• Circulate the water for at least 30 minutes to mix chemicals properly.

Brush and Clean Surfaces

• Use a soft brush or sponge to scrub all surfaces, including under the water line.

Extra Tips for Dealing With Severe Cases

Deep Clean the Filter

• Remove and rinse the filter thoroughly.

• Soak in a filter cleaner overnight if algae was heavy.

Consider Enzyme Treatments

• Enzymes help break down oils and organic material so they don’t feed algae.

Repeat Shocking if Necessary

• After 24 hours, test water again.

• If green persists, repeat shock treatment.

Preventing Green Water in the Future

Regular Maintenance Routine

• Test water 2–3 times a week.

• Keep sanitizer at recommended levels.

• Shock the tub weekly or after heavy use.

Keep the Tub Covered

• Use a tight-fitting cover to keep debris and sunlight out.

• Clean the cover regularly to avoid transferring grime back into the water.

Encourage Clean Bathing Practices

• Ask guests to shower before entering.

• Avoid lotions and oils that can cloud water.

Advanced Techniques for Stubborn Algae

Use an Algaecide

• Apply a spa-safe algaecide as directed.

• Best used as a preventative rather than a cure.

Professional Inspection

• If algae keeps returning, consider hiring a professional to inspect the spa for hidden issues.

Best Practices for Long-Term Water Clarity

Maintenance Log

• Write down each water test result and treatment.

• Track trends and catch problems early.

Seasonal Drain and Refill

• Drain and deep-clean the tub every 3–4 months.

• Clean all components including the filter and jets.

Keep Spare Chemicals Ready

• Stock up on sanitizer, shock, pH adjusters, and test kits.

• Store chemicals in a dry, cool place.

Common Mistakes to Avoid

• Neglecting regular water tests.

• Overusing or mixing chemicals improperly.

• Letting filters become clogged.

• Forgetting to clean hard-to-reach spots like behind the pillows or under seats.

By understanding what causes green water and how to treat and prevent it, you can keep your hot tub water inviting and safe for everyone to enjoy. Regular maintenance, proper chemical balance, and good habits make a huge difference in keeping green water away.