How to Treat Sudden Green Discoloration in Pool Water?

How to Treat Sudden Green Discoloration in Pool Water

Green pool water is usually caused by algae growth.

I. Types of Pool Algae

Pool algae generally fall into three categories: green algae, mustard algae, and black algae.

 The most common is green algae, which appears as a thick green soup floating on the water

 surface or clinging to pool walls, making surfaces slippery.

II. Three Causes of Algae Growth

1. Sunlight exposure

 Outdoor pools exposed to high temperatures and strong sunlight create conditions ideal for

 algae and bacteria growth.

2. Carbon dioxide

 Increased bacteria and organic matter cause dissolved oxygen levels to drop rapidly, creating

 an oxygen-depleted or anaerobic environment that promotes algae reproduction.

3. Nutrients

 Fallen leaves, dust, rainwater, and other organic debris enter outdoor pools, contaminating the water.

 In indoor pools, high bather loads introduce sweat, oils, skin cells, cosmetics, and other nitrogen-rich substances

 that feed algae.

Five Steps to Eliminate Algae

1. Algaecide treatment

First, add copper sulfate at 1–2 times the normal dosage. Under normal conditions, algae levels are low,

but when water turns green, algae are abundant, so a sufficient dose of algaecide (copper sulfate) is necessary.

After adding the algaecide, run the circulation system to ensure even distribution for maximum effectiveness.

2. Sanitization / disinfection

Approximately 2 hours after adding copper sulfate, add trichloroisocyanuric acid (TCCA) disinfectant at a rate

 of 4 kg per 1,000 m³ of water (compared to the normal maintenance dose of 2 kg per 1,000 m³).

This is a shock treatment (superchlorination) that thoroughly disinfects the pool water.

3. pH adjustment

After about 2 hours, test the water pH. Following rainfall and the use of TCCA (pool disinfectant),

 the pH level typically drops. Adjust accordingly.

4. Flocculation

In the evening, add a flocculant at 5–8 kg per 1,000 m³ of water. This will settle dead algae cells and

 other suspended particles to the pool floor.

5. Vacuuming

Early the next morning, before pool use, use an automatic pool vacuum to remove the settled debris 

from the bottom.

Following these five steps will restore clarity to the pool water.