Is green pool water really that bad? If your pool water is green, that means that it has algae growing in it. However, if you’ve ever gone swimming at a lake before, you’ll know that it’s no less refreshing than blue pool water, and feels fantastic on a hot summer day.
We do a lot of activities around green algae – we water ski on it, walk over algae covered rocks, ride ocean waves with marine algae. So it makes you wonder if it is safe to swim in a pool with green algae?
It is not a good idea to swim in a green pool. While green algae is not life-threatening, it can cause skin issues, physical injuries if you slip on its slimy surface, bacterial infections, and low visibility. Some side effects you can experience when swimming in a green pool include red skin, vomiting, nausea, diarrhea, and dizziness. If your pool is green, that means that the water chemistry is off and you need to shock it.
In this article, we will discuss the risks of swimming in a green pool, what it means when your pool turns green, how to deal with it, and how to know when it’s safe to swim in a formerly green pool again.
Types of green pool water
To get a gauge of how bad the problem is, see which of the following best describes your pool water’s color:
- Light green: This indicates that there is starting to be an algae problem, and usually occurs because of low chlorine levels or general improper pool maintenance.
- Medium green: A darker green color that starts to decrease visibility means there are more algae in the pool. More algae means more bacteria, which means worse symptoms and greater difficulty to remove.
- Dark/Black green: If the green is so dark that it’s borderline black, that signals severe algae growth and the presence of significant numbers of bacteria. This type of pool water is resistant to cleaning and can even leave stains on the pool walls after cleaning.
Why it’s not safe to swim in a green pool
It’s full of bacteria
Algae by itself is not harmful, hence why we can do activities like swim in green lakes without issue. In some cultures, eating algae is considered a delicacy, and I hear it’s quite nutritious.
The real issue here is bacteria. Just like how we can consume green algae, bacteria are also feeding on algae. It is these infectious agents that cause skin irritations and bacterial infections.
If your pool is green, that is a sign that there is insufficient chlorine to kill the algae and the bacteria feeding on them. There are possibly other viruses, parasites, and pathogens floating around in the pool water.
These can all enter your body through your eyes, nose, ears, throat, and even a small cut on your skin. The result is ear infections, nausea, diarrhea, fever, and countless other side effects that can ruin your fun in the sun.
Pools are closed systems
Building on the point above, the major difference between green pools and green lakes is that pools are closed systems, whereas lakes are constantly getting diluted with outside water sources and have a balanced ecosystem within.
Other than the occasional rain water or refill water, pools contain the same bacteria-filled water unless it is being treated with chemicals. Stagnant water is also more likely for algae to grow in it; pool water should be kept in motion even if it is not in use.
Conversely, lakes have a constant flow of water. The ecosystem contained within lakes and ponds also have microscopic aquatic life that can clean the water of toxins and bacteria. Comparatively, a pool is closer to a swamp than a lake.
The most common side effect of swimming in a green pool is skin irritation. It typically presents itself as redness of the skin, but it can also break out into severe rashes and cracks in the skin. These cracks can allow bacteria to enter, leading to a skin infection.
Algae is very slimy, causing surfaces you find algae on to be very slippery. This creates a dangerous slipping hazard resulting in bumps, bruises, cuts, and broken bones in severe cases.
If you happen to slip, injure yourself, and fall into the pool, that can lead to a risky situation where you are at risk of drowning. If you hit your head and fall unconscious, it doesn’t matter how good of a swimmer you are; you can drown unless someone notices you and rescues you.
As mentioned, bacteria can cause infections if you have an open wound, but also if you ingest it. This can result in symptoms such as fever, diarrhea, nausea, and other symptoms an infection can cause.
Warm, stagnant water is the breeding ground for bacteria to multiply, resulting in increased chances of infection. If you aren’t wearing goggles or water somehow gets into your eyes, you will be exposed to the bacteria and this can lead to eye infections.
When your normally pristine pool is covered in green algae, you’ll find that it becomes much murkier. Swimming in green pool water with low visibility has the same risks as anywhere else.
For one, it’s much easier to swim head first into the wall or other object since you can’t see it from a distance. You also can’t see how deep the water is and it is harder for you to orient yourself, so it can lead to plenty of confusion and accidents.
Another safety concern is if you are struggling in the water, the low visibility makes it harder for another swimmer to see you and rescue you. If you fall unconscious and stop moving, it takes a lot longer to find you and these crucial seconds that are wasted can mean the difference between life or death.
How to deal with a green pool
The best way to deal with most problems is to prevent it from happening in the first place. However, if prevention is no longer possible, then you will be forced to manually clean the pool.
Remove the waste
The first step is to clear any debris and algae from the pool using a vacuum with the filter set to waste. Afterwards, scrub the pool clean using a stiff brush to get rid of any lingering algae residue along the pool walls.
Adjust pH levels
Even though generally you want to aim for a pH of 7.5, when cleaning dirty pools aim for 7.2 instead. A good way to do this is by using sodium bisulfate to effectively reduce the pH level.
Shock the pool
Algae and bacteria thrive in pool water with low levels of chlorine, so you know what to do right? Pour chlorine into the pool to eliminate the bacteria and algae.
The shock product you purchase will come with instructions on how much to add with how much water. Wait an hour or two and let the chlorine work its magic.
Afterwards, test the water to see if the chlorine levels are sufficient. It should be around 5-10 ppm. There are chlorine test strips you can use to determine this.
Pump and filter the water
After shocking the pool, turn on the pump and leave it on for a full 24 hours. This allows the chlorine to disperse evenly and should produce optimal results after a day. If you’ve ever seen those time lapse videos, you can literally see the water slowly turn from green to blue.
However, if the pool still has a cloudy appearance, leave the pump running and use a stiff brush to once again scour the walls and floors.
Don’t worry about running your filter system 24/7 when you’re trying to clean up a green pool. The thing’s not going to explode. However, you should check on it 2-3 times a day, and backwash when the pressure gauge reads 7-10 lbs over clean.
Test for chlorine loss
If your pool still has some algae or is exposed to the sun after shocking, then the chlorine levels can drop too much too quickly. You must therefore constantly monitor the chlorine levels for a few days to see if they stabilize, otherwise run the pump a few more times.
The bottom line
Is it safe to swim in a green pool? After reading all of the above, the answer is a decisive no. The bacteria that the algae attracts is very dangerous and can cause bacterial infections that can harm your health.
If you notice that your pool is starting to turn green, then that is a sign that the chemical levels are dropping too low. You will need to shock it to kill the algae and bacteria already residing in the water.
Another reason for green algae is that you are not vacuuming or cleaning your pool often enough. You should also keep the water in motion, even if you are not swimming in the pool because stagnant water is a breeding ground for bacteria.
If all of this sounds like too much of a hassle, then you may prefer to hire a pool maintenance company to do this for you.