Why Do I Have Green Pool Water?


You’ve probably seen some picturesque pools on the internet, with their magnificent sapphire blue colors, and wondered, why doesn’t your pool look like that? 

While you shouldn’t worry much if your pool is not as blue as those you see online, a green pool is a cause for concern. 

Besides being embarrassing, green coloring can cost you a lot of money to clean up. 

Luckily, the problem is relatively easy to solve and even easier to prevent.

What Causes Pool Water to Turn Green?

The primary reason why your pool water is green is poor maintenance. Most likely, you do not clean the pool with chlorine or bromine as regularly as you should, or you don’t use enough of the chemicals when you do. 

Non-treated pools create the perfect conditions for algae to grow and spread, causing the green shade to cover the entirety of the pool.

Indeed, the accumulation of algae in your pool is probably not your fault, as natural elements like rain or wind can introduce them. Once in the pool, however, they feed off dirt and other organic elements like skin cells, bird poop, and pet dander. 

How to Eliminate Pool Algae

Before going further, it is important to note that algae will always be present in your pool, no matter how clean it is. 

As such, the key is not to eliminate them – which is impossible and dangerous – since any pool that can’t support life is also unsuitable for human use. 

Instead, the goal is to stop the algae colony from growing to the extent of changing the pool’s color. 

That said, algae removal involves three steps:

  • Vacuuming: Pass a pool vacuum to every corner of your pool to eliminate as much algae as possible. You should first set the pool filter to ‘Waste’ mode to get the best results.
  • pH balancing: The ideal pH should be 7.2-7.8, as this is the level where chlorine is more effective. So, take a reading of your pool’s acidity and if it’s below 7.2, treat the pool with soda ash. If it’s above 7.8, increase the acidity by adding Sodium Bisulfate or Muriatic Acid.
  • “Shocking”: It entails adding chlorine in high doses to significantly raise the chlorine levels in the pool. However, the shock product does not have to be pure chlorine to work – any pool cleaning product with a chlorine composition of 70% can do the job. Also, if your pool is dark green (that is, severely affected), you may need to shock it several times to regain balance. 
  • Scrubbing: If the pool remains discolored even after treatments, you may need to call a professional pool cleaning company to do a deep scrub to get rid of the green stains. 

Preventing Your Pool From Going Green

Keeping your pool sludge-free is a matter of cleaning the pool as regularly as you can. Brush the pool at least twice a week and use specialty chemicals while at it. 

You will also want to keep chlorine at the recommended level and occasionally use algaecides to inhibit the algae life cycles. Installing larger filters also helps, as they filter out the tiniest organisms more effectively.


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