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Why Is My Pool Green and How do I Fix It?

So, you wanted to go swimming but your pool had other plans? Not to worry, green pool water is common and can be easily corrected in a few day’s time.

Green pool water comes from algae growth. It’s not going to turn you into a mutant, but you definitely don’t want it in your pool.

Algae is a plant that thrives in warm, sunny weather. It can go from microscopic, to light green, to deep green overnight. When the pool’s sanitizer levels are too low, algae has an opportunity to thrive. This situation can be created by a chemical imbalance or lack of chlorine so it’s important to test your water regularly.  When chlorine levels drop below 1ppm it creates a fertile environment for algae to grow.

To take your pool from green to clean, we have a few simple steps and a handy infographic.

Before you get too excited, take a look at your clothing. You’ll be working with chlorine, which can bleach your clothes, so make sure it’s something you can afford to get dirty (or clean, depending on how you see it).

1. Start by vacuuming up the free algae and debris from your pool.

Set your filter to Waste and vacuum up as much algae and sediment from the bottom of your pool as possible. Some algae leads to more algae, so it’s important to get rid of what you can.

2. Brush your pool with an algae brush to break it off surfaces.

Algae will cling to surfaces like floors and stairs so a hard brush will work better to scrape it off. You need to free the algae from these surfaces in order for the shock to do its job in a few steps. Make sure you give this part a good effort. Whatever you leave behind will be the start of next week’s algae problem.

3. Test your pH and alkalinity levels.

Use your test strips or kit to get a read and write down what levels you are working with. A good PH for a pool is around 7.5, but fort his task it would ideally be around 7.2. Once you know what the PH level is you can use pH Up or pH Down to balance it.

Now is also a good time to assess the “greenness” of your pool to determine how much shock to use. Light green, double shock, dark green, triple shock, swamp green, quadrupole shock. But seriously if your pool water is black-green, you might want to call the your local pool guys in for back up.

4. Give your pool a “shock” to kill algae and return the water to normal chlorine levels.

There are many different pool shock options so make sure you’ve got the right tool for the job. Pool shock contains a high level of Chlorine that will kill the algae but it’s different than the Chlorine you would use for everyday maintenance. For an algae problem, we recommend a pool shock that contains Calcium Hypochlorite, which has 65% “free chlorine”.

Pro Tip: always add shock to water, never water to shock.

When Calcium Hypochlorite mixes with algae microbes and other organic cells, the chlorine compounds it contains bond with the natural enzymes and disrupt cell function. This effectively kills the bacteria, causing the cells walls to rupture and your pool sanitization to be restored.  When the Chlorine does this, it gets used up, becoming “captured chlorine”. Your pool’s total chlorine is the sum of its free chlorine plus captured chlorine. Once captured, chlorine will not do any more work to clean your pool.

A little more chlorine knowledge to impress your child’s chemistry teacher

Unlike your day-to-day sanitizer, calcium hypochlorite contains “unstabilized chlorine” which just means it does not contain any cyanuric acid and can be burned away by sunlight. That’s why you’ll want to do this in the evening.

Calcium hypochlorite works with your regular chlorine maintenance by reactivating sanitizers that get trapped in organic materials like skin cells, body oils and dead leaves. The bonds create “chloramines”, the compounds responsible for pool smell (that’s the scientific name) that can irritate skin and eyes. Pool shock in combination with chlorine keeps your pool clean and helps deal with the used-up chlorine sitting in your pool.

5. Turn your filter on and let the filter run for at least 24 hours.

Once you’ve double or triple shocked your pool, turn your setting back to filter and let the filter run for at least 24 hours and up to 5 days to remove dead algae and dissipate the shock. If you’re a little impatient and want to clear up the cloudy pool faster, a good pool clarifier is your friend.

6. Test for pH, Alkalinity and sanitizer levels.

When your pool water returns to normal, test the water and adjust as needed to maintain its regular balance.

“And Stay Out!”

Yelling at the algae won’t keep the water clear but maintaining proper sanitization levels will. Test your waters at least once a week and keep your chlorine levels stable. To be extra cautious, treat your water with algaecide during your weekly maintenance and avoid letting algae grow into a problem.

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