50 Shades Of Green...Swimming Pools
Swimming pools by and large are supposed to have a blue tint to the water. Many pool owners mistakenly think that the blue color in the water is a reflection of the blue color of the sky, or perhaps reflecting the blue color of the tile band around the perimeter of the pool...but both of these guesses are incorrect. Pool water looks blue even in indoor pools that have no windows, and even if the pools are 100% white with white accent tile, the water still appears to be blue - especially in the areas where the water is deepest.
In short this color effect is due to how light colors are absorbed by water. White light, or natural light, contains an equal mix of light colors from all ends of the spectrum. However when this white light reaches pool water, for example, the longer wavelength light colors (red, orange) are readily absorbed by the water which leaves an abundance of green and blue light wavelengths in the water. The end result is that the color of the water appears to be blue / green. For more information about how this works you can read this article that talks about why black pool liners still look blue when they are full of water.
So now that we know why swimming pool water looks blue let's look closer at green swimming pool water and what can cause the various shades of green you can find in pools:
Hint Of Lime Green
Hint of lime is the first shade of green that your swimming pool will turn if you let the chlorine levels drop to zero. Without any available sanitizer in the water the organic debris will begin to grow which results in plant matter called algae existing within the water and stuck to the walls and floors of your pool. This plant matter will result in the pool water having a slightly green tint while still being relatively clear. This shade of green is commonly found the day after heavy rains if you neglected to add extra chlorine to account for the rain water using up the free chlorine that would normally be in your water.
Minty Fresh Green
After 24 to 48 hours without any sanitizer in the water your pool will develop a distinct minty flavor to the water. This refreshing and zesty flavor is due to continued growth of plant matter in the water, which has now started to negatively affect the other water chemistry variables such as the pH and total alkalinity which continue to drift further and further from the ideal water chemistry ranges which you can read more about in this article about pool water chemistry. While no longer good for swimming, the water in the pool is now supercharged with organic growth and excellent to use for watering lawns and gardens.
Emerald Lagasse Green
By the end of the first week your pool water now resembles a beautiful emerald color. The flavor of the water has continued to develop crisp profiles of apple with hints of black licorice and e-coli. Salt water pools will have a more developed flavor profile due to the salt helping to enhance the natural flavors in the water. While a beautiful and vibrant green color now, you can no longer see through the water to the floor of the pool. I mean, it's down there somewhere so no need to get bent out of shape over it, but if you drop anything in now it belongs to the pool.
Spicy Olive Green
By week two with no chlorine in your water the beautiful and bright emerald color will have faded to a more dull olive green color. The flavor profile of the water has now progressed to tasting hot, despite being cold, with a distinct olive flavor. You can either start adding bucket loads of chlorine to the water to try to clear it up, or add 10,000 gallons of gin and 10,000 gallons of vermouth to your pool. With 40,000 gallons of martini in your backyard you can now accomplish your dream of being the most popular person in your neighborhood. Start sending out party invites!
At the end of the first month without chlorine in your pool the water has now progressed to a bright green color similar to emerald, however the water is now completely turbid with no ability to see past the surface of the water. At this point it will take a huge amount of chlorine and some luck O' the Irish to get your pool water clean and clear again. As an interesting factoid, it is rumored that this is how McDonalds makes those Shamrock shakes that come out every March...they stop adding chlorine to the vanilla shakes some time near the end of January.
In month two your pool has progressed from a tranquil blue oasis to a peaty bog. The water now more resembles a solid rather than a liquid and it might be temping for you to try to walk across it. Such is the fate of many a small animal or wayward wanderer. By the time you realize that the soft soil has given way to a sticky, inescapable doom it is already too late. The stinky bog that once was your swimming pool now sits silently as a deadly trap for any creature that mistakes it for stable soil. The plumbing for your pool now acts as an underground rodent superhighway for critters looking to travel between different areas of your backyard.
Swamp Thing Green
Month three with no sanitizer in your pool has resulted in the development of a swamp, complete with plant and animal life, and teeming with insects and parasites of all descriptions. The water in the pool tastes like blood, because the only reason you would be in this water is if you were dragged in by a man eating crocodile, which is entirely possible at this point. The local bylaw authority issues an ordinance to have your pool cleaned, however this was trumped by the order from the local environmental protection agency to preserve your backyard swamp after the discovery of a previously unknown form of tapeworm was found growing in the water.
Dead Forest Green
At six months your pool now resembles a haunted forest more than a swimming pool. The peat bog eventually stabilized and the soil started to support larger growth saplings and underbrush. Eventually larger mammals moved into the area to feed on the abundance of rodents and smaller mammals and now you are too afraid to go in the backyard alone. At night you can hear the call of the wild as a migratory wolf pack has set up a permanent residence in your haunted forest. People in the neighborhood have started hanging posters of their missing pets. You tried adding 10L of liquid chlorine to the forest but it did not seem to make much of a difference.
After the wolves all died from intestinal parasites the government ended up putting your yard under a permanent quarantine. There is talks about building a concrete sarcophagus over your property to protect the toxic soup from radiating into the surrounding neighborhood. The smell from your pool is now strong enough to kill a healthy buzzard in full flight and your neighbors have taken to candlelight vigils around your biohazard in an attempt to pray away the evil. Your family and friends all stopped associating with you, you lost your job because you smell like rancid swamp water, and your dog has had pink eye for almost two months. If only you could go back in time and put some chlorine in the pool all of this could have been avoided, but you wanted to have a "natural pool". Maybe you should take a minute and read this article about pools without chlorine and learn more about why all of this happened.
Famous frogs and swimming pools have this in common - it's not easy being green. Instead of letting your pool go and constantly fighting the quality, clarity and color of your water, what you want to aim to do is never let the level of free chlorine in your pool drop to zero. Experienced pool owners know that maintaining a pool can be easy, but if you let the water start to get away from you then this is how you end up with green water. Once your water quality has deteriorated to this point you will now need to fight to get it clean again. Without a doubt the easiest way to maintain a pool is to simply keep an eye on your free chlorine levels and never let them fall to zero. If you manage to do this one thing you will be able to avoid the vast majority of water color and clarity problems.
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