What Affects Pool Water Color?

When installing a new pool, there are hundreds of large and small decisions to make. One decision that you’ll notice every time you look at your pool is the pool finish. Different finishes can affect the color of your pool water, so picking a finish is a major decision. But many factors besides the finish also affect the pool water color, so it’s difficult to predict precisely what color your pool water will be until you actually fill the pool.

What Affects Pool Water Color [infographic]

What Gives Pool Water It’s Color

It’s obvious when you stop and think about it, but it bears saying: water (when it’s clean) is clear. Many homeowners get all caught up in the color of their pool water, but the truth is it’s all an optical illusion. The water is (or should be) clear. What you see is a result of how water bends the light that enters the pool and reflects of the pool finish.

When sunlight hits the pool, two things can happen. It can be reflected back, or it can keep going into the water. Of course, it can also do both. Or, to be more technically correct, a part of the light can reflect back and a part of the light can keep going. White light, as you may remember from your middle school science classes, is made up of a spectrum of light. Long wavelengths are red. Short wavelengths are blue. Very short wavelengths are invisible UV rays, while very long wavelengths transmit heat.

When broad-spectrum light, such as sunlight, hits your pool, some of it bounces back and some penetrates the surface of the water. When we see an object, what we are actually seeing is the part of the light spectrum that has bounced back off of that object and hit out eyes. The reason pool water looks shiny is that light is hitting the pool and bouncing back at you. When you see your reflection, that’s the light that is bouncing off of your body, hitting the pool, and then bouncing back to your eyes. The light is literally reflected back into your eyes.

Size Matters

One major factor in the apparent color of your pool water is the size and depth of your pool. We say “apparent color”, because water is, after all, clear. But the depth of the water will affect how much refraction you get from the bottom of the pool. The same pool finish will produce a darker, more vibrant hue in a large, deep pool than it will in a small or medium-sized shallow pool. You can see this effect when you look out at a clear tropical sea. The water closest to the beach is nearly transparent. As you look out, the water turns turquoise. Looking further, where the seafloor drops of and the ocean becomes deep, the water will somewhat abruptly change colors to a rich, dark blue.

There are some ways to get a darker color in a smaller pool. The most obvious factor is to use a darker, richer color in your finish. But no matter what color you use, you should be aware that a shallower pool will never look like a deep one. Also, beware of pictures in brochures online. Light is affected by so many factors that it is rare to get an exact reproduction of the same color in any two pools.

Even in a deep pool, shallower areas will have a different color than deep ones. In very shallow areas, like steps and ledges, the water will be clear, and you will just see the finish. In slightly deeper areas you will begin to get some color to the pool water, but it will be subtle until the water gets a bit deeper.

Even if you use a black finish, your water will be darker than if you use white, but the difference will not be as great as you might imagine.

Reflecting Your Surroundings

The apparent color of your pool water is also strongly affected by the pool’s surroundings. A pool surrounded by lush greenery will appear more green, regardless of the pool finish. If a pool sits in a landscape of bright green lawns and perennially green evergreen trees, they will cast a reflection. On the other hand, if your pool is situated in the midst of a stark white sandstone hardscape, your pool water will look much lighter.

Since water is actually transparent, its apparent color is part physics and part optical illusion. The physics part explains the effect of reflection. But the optical illusion part is just as important. A pool that is exactly the same color can look different when surrounded by different colors. Don’t believe us? Try these optical illusions on for size. As you can see, a single color will look brighter when surrounded by darker colors and darker when surrounded by lighter colors. So the color of pool water can be changed simply by changing its surroundings.

Shifting Sunlight Affects Pool Water Color

This one may seem obvious, but it’s important. The color and angle of the light coming from the sun can have a considerable effect on the apparent color of pool water. The optimal setting to get the full brightness of your pool finish is direct sunlight on a clear day. When the sun is low early and late in the day, or when it is overcast, you will bet a much more muted color. Also, water doesn’t just reflect the objects around it, it reflects the sky above it. So a gray sky means a grayer pool water color.

If your pool is in the shade some or all of the time, you probably won’t get the color you may have seen in a catalog or online. Most pictures of pool finishes are taken under clear blue skies when the sun is high and the shadows are nonexistent. If you’re looking at your pool and those aren’t the current conditions, you shouldn’t be surprised that the color is different.

Artificially Coloring Pool Water

While sunlight and pool finishes are mostly what affects the color of your pool water, there are other options. If you will be using your pool at night, sunlight is no longer an issue. For some truly stunning and unique effects, you can install colored lights in your pool. With artificial lights, you can choose any color, or even shifting colors. Lights placed underwater in a pool can cause the whole pool to glow in whatever color you choose.

If you’re in the mood for something really different, try coloring your pool a completely unique shade during the day. Pool dyes can temporarily turn your entire pool into completely artificial colors. This is great for a themed party.

Pool Water Balance Affects Color

All of the above suggestions and explanations assume that your pool water is truly clear. But as any pool owner knows, the water is not always clear. If your pool water is looking scummy or green, you probably have a problem with how your pool water is balanced. Murky water can be the result of algae or other organic material that grows in a pool that is not sufficiently clean. That could be due to water that does not have enough free chlorine or a problem with the filtration and water circulation system. Another cause of murky water is minerals in the water. It is possible to have too much calcium in the pool water. Also, if you use well water, there may be mineral and metals in the water that affect the color.

If you’re worried that there is something wrong with your pool water, The Pool Butler is here to help. We can diagnose pool problems and make repairs when necessary. We can also perform regular maintenance to keep your pool water crystal clear. With clear water, you can get the color you hoped for.

The Pool Butler