Why is my pool green?

Why is my pool green?

A green pool is an unpleasant sight and may result in a severe problem if overlooked. Luckily, this nuisance is not very tough to handle. 

Learning about the cause, following the correct procedure for eradication, and taking preventive measures will end this problem for good. 

Read further to find out how to fix green pool water. 

Why is your pool green? 

About 99% of the time, the reason for that green and cloudy pool water you have is algae. 

The most common type of algae that affects pools is green algae. There are also yellow and black algae that are less common depending on where you live, but they are more problematic. 

A single algae spore is impossible to see with the naked eye, but they multiply quickly to create green, cloudy water. A prominent characteristic of algae-infested water is the sliminess of the pool walls. 

Algae is part of the natural ecosystem and will eventually find a way to get into your pool or spa water sooner or later. 

However, a big reason for ending up with green water is the uninhibited growth of algae due to having a low level of sanitizer in the water.

Chlorine is what effectively kills algae and other microorganisms that invade pool water. Additionally, the pH levels may be too high and that can stop the sanitizer from doing its job. 

High levels of algae in the water can be hazardous to skin health and may cause issues with pool filtration and circulation. So, it is imperative to get rid of algae from your pool and keep it from coming back again

If your water is properly sanitized and the surface of the pool isn't slimy then, you most likely have copper in your water from either copper pipes in the plumbing or using a copper-based algaecide. 

High quantities of copper in the pool water can react with the pool oxidizer (shock), resulting in clear water with a green color.

How can you fix it? 

Fixing a green pool is simple, although it can take anywhere from three to four days. Follow this step-by-step procedure to eliminate the chances of mistakes. 


Test the Water

Use a liquid test kit to check pH and total alkalinity levels. These parameters must be at the optimum levels for the process to work, so you’d want the pH to be between 7.2 and 7.5, and the total alkalinity between 80-100. Use a pH increaser or pH decreaser to adjust the pH levels, and follow these guides to lower or raise the total alkalinity of your pool water

Clean your pool


Clean the Pool

Use a pool net to skim any floating algae or debris. Then use a pool brush to scrub the sides so that the sticky algae on the pool walls come off. 

It is also good to backwash your filters or clean your cartridges, they may already be in a pathetic condition, and cleaning them will help with better circulation while shocking


Shock the Pool

The chemical responsible for killing algae in a pool is chlorine. Shock your pool with a double-than-normal amount of shock and keep the pump running until your water clears

Tip: Always shock the pool at night because the sun depletes the chlorine quickly. Plus, you won’t have to sit and wait for the chlorine to work before proceeding to the next step.  

Use of an algaecide after the shock is also unnecessary if you keep your chlorine level within range and your water chemistry balanced. 


Vacuum and Balance

Check the water for signs of living algae the next day.

If you find any signs of it, shock the pool again, and keep repeating the process until your water is clear again. You must also vacuum your pool to remove any dead algae that may have settled down on the floor.

When it looks clear, check and balance the water chemistry. 

How can you prevent it from coming back? 

An ounce of prevention is better than a pound of cure, and the same is true for your pool. Here are some things to help you avoid algae outbreaks :

  1. Keep your pool covered if possible, especially when you do not intend to use it for longer durations. 

  2. Always keep an eye on the water chemistry.  To do this, you can consider using our Sutro Pool Water Monitor. Sutro tests your water three times per day and can notify you of an issue with your chemistry before algae even have a chance to think about invading. 

  3. Ensure your filters are always clean by following a regular filter cleaning schedule

  4. Follow a strict maintenance schedule for your pool. Routine brushing,  an inspection of your equipment, visual water checks, and frequent water testing will help prevent any future issues.
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