Why Is Pool Water Blue?

Posted on: 13 November 2015

Blue water has a pristine, clear appearance even though it isn't technically "clear." Pool owners dedicate much of their maintenance to keeping their water looking its bluest. But why do pools have a blue hue? 

‚ÄčIntrinsic Color 

While you probably think of clean water as colorless, this isn't the case. When you observe water without color pollution sources, such as light reflecting off brightly colored surfaces, the liquid has a pale turquoise color. 

This natural blue color, like almost all other colors, results from the way water absorbs light. White light, like sunlight, actually consists of a rainbow of colors. When white light hits water, all the colors in this spectrum are absorbed except blue, which makes the water appear tinted. The deeper the water, the less light exposure it receives. This phenomenon is why deep water looks dark, while shallow water looks paler.

Mineral Content

The natural color of water is affected first by the water's contents, especially any minerals or growths present. For example, the Colorado River appears red due to iron-rich silt suspended in the water, while the Red Sea gets its color and name from red algae growth. Similarly, your pool water changes colors according to the particles, plant life, and chemical composition present in it.

Pool chemicals, including chlorine and salinization solutions, discourage the growth of unwanted plants, while regular cleaning removes items that deposit particles to keep your water blue.


In addition to your water's inherent color and chemical composition, your pool can appear more or less blue when it reflects specific objects. Color pollution objects may include:

  • Decking or sidewalk materials
  • Pool goers 
  • Pool tile or lining
  • Toys and pool accessories
  • Walls, gates, or building exteriors

Even a particularly blue sky could make your pool water appear brighter and bluer. If you struggle to maintain an attractive water color in your pool, you can use the water's reflective qualities to your advantage. To get a bluer hue, re-tile or reline your blue with complimentary colors--like teals and greens--or contrasting colors--like oranges and reds. You can also install dark landscaping and exterior elements, such as a black-brown wooden pool deck, to make your pool's water look lighter and cleaner.

If your pool water unexpectedly changes color, call in a swimming pool service like Guaranteed Pool Service & Repair. A professional can help you diagnose and treat the causes of green, brown, or murky pool water. For most pool owners, a thorough cleaning and chemical treatment change are all it takes to create bluer waters.