Clear pool water with a green tint may be from pollen, chlorine-resistant algae, or most often from a too-high pH level. When a pool's pH is over 7.8, even high levels of chlorine destabilize and cannot sanitize, and metal in your water and pool components can oxidize, giving off a greenish hue.
The pH may be too high.
If you're not checking the pH and it has risen too much, you could be adding the right amount of chlorine, but it can't work correctly, and algae will begin to grow. In this case, you'll need to add a pH reducer like sodium bisulfate or muriatic acid to bring the pH down to the correct level.
There are a lot of reasons why algae keep returning to pools. The most common of these reasons are: Low levels of chlorine or chlorine getting burned up too fast before it gets the opportunity to kill the algae.
Test and balance your pool water weekly. The ideal pH range for swimming pools is 7.2 to 7.6. Check your filtration system weekly to ensure it's working to properly circulate the water. Brush the pool surfaces (walls, floors and steps) weekly to remove algae that may be building up.
Chlorine is still one of the most effective killers of algae so doing a super-chlorination of 10-20 ppm of chlorine can go a long way towards wiping out the algae. Liquid chlorine is an ideal shock for algae because it is fast acting and does not add cyanuric acid (CYA) or calcium to the water.
Adding shock to your pool super-chlorinates your water. And this extra dose of sanitizer will kill algae growth. The more serious your pool algae problem, the more shock you'll need. We recommend using calcium hypochlorite shock, or cal-hypo shock, as an effective algae treatment.
Whether mild or severe, it isn't recommended. Significant amounts of swimming pool algae welcome a breeding ground of harmful bacteria that feed on algae. These bacteria pose health risks to swimmers, most commonly resulting in a skin rash. It can also cause various bacterial infections of the ears or eyes.
Shock Your Pool
Shocking is the process of adding chemicals to your pool to raise chlorine levels and kill bacteria and algae. We recommend using a calcium hypochlorite shock to treat your algae problems.
How long will it take to clear the pool? A fiberglass pool in its worst condition can be algae-free in 24 hours. For a vinyl liner pool, the process can take 3-4 days. For a concrete pool, this can take a week or more.
Rainwater itself does not cause algae, but it can provide the right environment for algae.
Surprisingly enough, too much chlorine can also cause your pool water to discolor, but no algae can grow in water with high chlorine levels.
So, this one is kind of obvious, but chlorinated water does not grow algae. If you always keep your chlorine levels consistently between 3-5 ppm your water will stay blue. This means you should use a basic test strip 2 to 3 times a week to make sure that the chlorine level is where it needs to be.
Water with a high pH level reduces chlorine's effectiveness. This can lead to other problems like cloudy water and algae buildup.
Once algae gets into your pool water, they can turn into an algae bloom if you have nitrates, out-of-balance chemicals, warm temperatures, sunlight, carbon dioxide, or phosphates. Poor water circulation, poor filtration, and not sanitising your pool will also contribute to rapid growth.
Bleach is great for killing algae (and other organisms that may lurk in your tanks) and for keeping it from coming back.
When temperatures reach below 40°F algae growth is stopped, but it can still survive and become dormant over the winter. Pool algae will come back to life weeks before you decide to open your pool.
Algae create a chlorine demand in the water for itself, consuming chlorine that should be working on other contaminants. As it expels carbon dioxide, the pH level of pool water can rise. Algae are kind of like weeds in your garden.
Also, if neglected over a long period, bacteria associated with algae can be a health concern. Running your filter when the pool is covered with algae can clog up the filter and even damage it permanently.
Can you over shock a green pool? No. The more chlorine shock you add to a green pool, the better chance it has to kill off all the algae. Follow the normal shock treatment based on the size of your pool and you can double, triple, or quadruple the dose to kill algae.
It's often recommended to shock your pool once a week. If you don't do it every week, you should at least do it every other week. This is necessary to maintain your pool's water chemistry. If you have a lot of people over in your pool or have a party, you may want to shock your pool more frequently.
Chlorine shock is usually the best way to get rid of green algae. However, an algaecide may become necessary if you're fighting more chlorine-resistant algae, such as mustard algae or black algae. Even then, the pool algaecide should work with chlorine or other sanitizers – not as an alternative to them.
In general, add one pound of shock to your pool for every 10,000 gallons of water. But if you're experiencing an algae problem, you'll need to add double, triple, or quadruple the amount of shock.