"Heavy rain dilutes pool chemicals, especially salt and chlorine, which causes the pool to turn green.
Rainwater itself does not cause algae, but it can provide the right environment for algae. Rain will bring phosphates, nitrates and other organic contaminants into the pool. As we discussed earlier, rain also reduces chlorine levels.
Green pool water is often caused by the presence of algae in your pool. Algae blooms can appear when your pool has a low Free Chlorine. Exposure to high heat, heavy rain or poor circulation, without the use of a preventative algaecide, also increase your risk of developing pool algae.
The most common reason pool water turns green is due to algae growing in the water. Algae can grow rapidly, particularly in hot weather, which is why it can surprise you overnight during the warmer months. This generally comes down to an imbalance or lack of chlorine in the water.
What's important for you to know: You shouldn't swim in a pool that's green until you test the chemical levels, like the officials in Rio did before the diving event began. It's the balance of things like chlorine, pH, and alkalinity in a pool that keeps it sterilized.
The free chlorine levels might be low.
But be careful—adding too much chlorine in pool water can cause those metals to oxidize and turn the pool a different shade of green.
Shock the pool with chlorine every day until all the green is gone (possibly 3 to 4 days). 2. Run the filter 24 hours a day and backwash every day until the green and then cloudiness is gone (usually up to 7 days, sometimes as long as 2 weeks depending on the filter). 3.
Combined with sunlight, these conditions are perfect for algae and other contaminants to grow and affect the health of your pool, turning it green overnight. If your pool has turned green after a rainstorm, consider visiting your local Poolwerx for a free water test and pick up some Vitalyse Poly Plus Algaecide.
Shocking your pool isn't necessary, although, it's not a bad idea either. If you get an extremely heavy rain fall, you could shock your pool for good measure. This will help fight off any contaminants that the rain may have brought to your pool.
Remember that shocking alone does not clear up a green or cloudy pool; that is what the filter is for. It doesn't matter how much shock you put in the pool if you have a bad filter.
Baking Soda and Green, Blue, or Yellow Algae
You'll need to use an algaecide to kill the algae and superchlorinate your pool to clear the water. After this treatment, test your pH and alkalinity and add baking soda to raise alkalinity to at least 100 ppm and pH to between 7.2 and 7.8.
Pools can immediately turn green after shocking when they have metals like copper in the water. These metals oxidise when exposed to high levels of chlorine which makes the pool water turn green. Adding a metal control product such as Zodiac Metal Remover will help to restore the pool water.
The pool turned green from copper, not algae
Think of the Statue of Liberty. It is made of copper, and has turned green over time through oxidation.
Pool water turns green because of algae in the water. Algae can grow rapidly, particularly when it's warm like Summer, which is why it can surprise you overnight. This generally comes down to an imbalance or lack of chlorine in the water.
Effect on Pool Water pH
Since rain is diluting your pool, you may expect that it will reduce the acidity of your pool water. However, all rain in the US is acidic due to pollution, so rain actually decreases your pool's pH – in other words, the pool water becomes more acidic.
Rain almost immediately causes the pH (Potential Hydrogen) in the pool water to rise while also reducing the TA (Total Alkalinity) slightly via dilution. Higher pH will cause more of the chlorine in a pool to become inactive or “fall asleep” reducing it's effectiveness.
The extra filtering will help clean out the impurities rain has introduced into your pool's water. Pool pumps are made to withstand rain and it is beneficial to run your pump during or after rain.
In theory, if you have a cloudy swimming pool, you can add chlorine to “shock it” and clear things up. Chlorine will get the job done. But, the amounts may vary and you may have to really pound the pool with chlorine to get the water totally clear.
Algaecide will be able to help you clear cloudy green pool water such as this. Algaecide, to put it simply, is a pool chemical that can kill algae or prevent it from growing in your pool.