How to Get Rid of Green Water in a Swimming Pool

How to Get Rid of Green Water in a Swimming Pool

Green water in a swimming pool is not only unattractive, but it can also pose health risks and damage pool equipment. Typically, green water is the result of an algae bloom, which occurs when the water chemistry is imbalanced, and the pool is not properly maintained. In this comprehensive guide, we will discuss the steps necessary to get rid of green water in a swimming pool and restore crystal clear water for a safe and enjoyable swimming experience.

Identifying the Cause of Green Water

Green Algae

The most common cause of green water in a swimming pool is the presence of green algae. Algae are microscopic aquatic plants that multiply rapidly when the conditions are favorable, such as warm temperatures, excess nutrients, and imbalanced water chemistry.

Imbalanced Water Chemistry

Improperly balanced pool water can lead to green water, as it provides an ideal environment for algae growth. Some key factors that contribute to imbalanced water chemistry include:

Inadequate sanitizer levels (e.g., chlorine or bromine)

Improper pH levels

Insufficient total alkalinity and calcium hardness

Poor Circulation and Filtration

A poorly functioning circulation and filtration system can contribute to green water, as it allows algae to proliferate and reduces the effectiveness of pool chemicals.

Steps to Get Rid of Green Water in a Swimming Pool

Test and Balance Pool Water Chemistry

Begin by testing your pool water using a reliable pool test kit or test strips. Adjust the water chemistry to the following recommended levels:

pH: 7.4 to 7.6

Total alkalinity: 80 to 120 ppm

Calcium hardness: 200 to 400 ppm

Chlorine: 2 to 4 ppm (for a chlorine pool) or 30 to 50 ppm (for a bromine pool)

Use the appropriate pool chemicals to adjust the levels, such as pH increasers or decreasers, alkalinity increasers, calcium hardness increasers, or chlorine stabilizers.

Shock Your Pool

To kill off the algae and other contaminants in your pool, perform a shock treatment using a high dose of sanitizer. Follow these steps:

Select a pool shock product suitable for your pool type (chlorine-based or non-chlorine shock).

Refer to the manufacturer’s instructions to determine the correct dosage based on your pool size and algae severity.

Add the pool shock to your pool water, ideally in the evening when sunlight is less intense, to prevent the shock from breaking down too quickly.

Allow the pool shock to circulate for at least 8 hours or as recommended by the manufacturer before swimming.

Brush and Vacuum the Pool

Use a pool brush to scrub the walls, floor, and other surfaces of your pool to dislodge dead algae and debris. Follow up by vacuuming the pool using a manual pool vacuum or automatic pool cleaner to remove the debris from the pool floor. This helps prevent algae from reestablishing and improves the effectiveness of pool chemicals.

Clean and Backwash Your Filter

Algae can clog your pool filter, reducing its efficiency and contributing to poor water quality. Clean your filter according to the manufacturer’s instructions, which may involve rinsing the filter cartridge or backwashing a sand or diatomaceous earth (DE) filter.

Monitor and Maintain Water Chemistry

After the initial treatment, continue to test your pool water regularly (at least once a week) and adjust the chemistry as needed to maintain the proper balance. This helps prevent future algae blooms and ensures clear water.

Preventing Green Water in the Future

Maintain Balanced Water Chemistry

Regularly test and adjust your pool water chemistry to keep it within the recommended ranges. This helps create an environment that is less conducive to algae growth. Test your pool water at least once a week and after heavy use, rainfall, or adding significant amounts of water.

Optimize Circulation and Filtration

Ensuring proper water circulation and filtration can help prevent green algae growth by distributing pool chemicals evenly and removing debris. Run your pool pump and filter for at least 8 to 12 hours per day, or as recommended by the manufacturer. Regularly clean and backwash your filter to maintain optimal performance, and consider using a pool circulation enhancer, such as a pool return jet or water feature, to improve water movement.

Use a Pool Algaecide

Incorporate the use of a pool algaecide as part of your regular pool maintenance routine. Algaecides are specially formulated chemicals that help prevent the growth of algae in your pool water. Follow the manufacturer’s instructions for the proper dosage and application frequency. Be sure to choose an algaecide that is compatible with your pool type and chemical treatment system.

Remove Organic Debris

Promptly remove leaves, grass, and other organic debris from your pool using a pool skimmer or leaf rake. This helps reduce the nutrients available for algae growth and maintain a cleaner pool environment. Additionally, vacuum your pool floor and brush the pool surfaces at least once a week to remove any buildup of dirt and algae.

Maintain Pool Surroundings

Keep the area around your pool clean and free of debris to minimize the introduction of algae spores and other contaminants. Trim back trees and plants to reduce the amount of organic material that can fall into your pool, and consider using a pool cover when your pool is not in use to protect it from debris and sunlight, which can promote algae growth.

Regular Pool Shock Treatments

Perform regular pool shock treatments to help maintain sanitizer levels and kill off any algae spores that may be present. Shock your pool at least once every 1-2 weeks, or more frequently during periods of heavy use, after rainstorms, or if you notice the early signs of algae growth.


Getting rid of green water in a swimming pool involves addressing the root cause of the problem, typically algae growth, by balancing water chemistry, shocking the pool, and thoroughly cleaning the pool and filter system. Once the green water issue is resolved, adopting a comprehensive pool maintenance routine can help prevent future algae blooms and keep your pool water crystal clear. By regularly testing and adjusting water chemistry, optimizing circulation and filtration, and maintaining a clean pool environment, you can enjoy a pristine swimming pool all season long.