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Close-up of green algae in water

Prevent Green Pool Problems with Winter Maintenance

Pool Maintenance Tips to Prevent & Treat Green Pool Water

The winter months can be tough for pool owners. Unless you’ve got the luxury of a heated pool, you’re stuck waiting to use your pool until things thaw out and warm up in late spring, when you can finally schedule your pool opening services.

Even still, pool opening in the spring brings with it the potential for a whole host of maintenance and care issues. Chief among these issues is the dreaded green water of an algae-filled pool.

While green pool water can be caused by a number of factors, a bit of pre- and post-winter maintenance (not to mention a few things you can do during the big chill) can help prevent frustrating green water when it’s time to reopen.

Issues with a pool’s chemistry can be dealt with during the pool closing season to ensure everything’s good for the eventual opening.

So if you’re always wondering, “Why is my pool cloudy and green?” in spring during pool opening, consider these tips to keep things crystal clear!

Why is My Pool Green?

Pool water turns green due to an abundance of algae. Algae growth is a common, natural occurrence in standing bodies of water, but you definitely don’t want this in your pool. Algae in pool water usually means something’s gone wrong with the chemical balance in your pool.

If the water left in your pool during winter months doesn’t freeze, there’s a chance algae can grow and develop in the water, despite the cooler temperature. That’s why it’s so important to shock the pool when you close up at the end of the season. If your pool water chemistry is unbalanced, the water can become a cozy home for algae to thrive in.

What’s more, pool water chemistry can become unbalanced if contaminants get into your pool over the winter, if the temperature of the water rises, and if there aren’t sufficient winterizing chemicals used during pool closing and throughout the winter.

Maintaining Pool Chemical Balance

To prevent algae growth and to ensure your pool is crystal clear when you open it next spring, you will need to maintain the pool’s chemical balance over the winter or until the water freezes.

There are a few ways to ensure you’ve covered your bases when it comes to pool chemical balance, which will help prevent algae blooms during the long winter months. Let’s take a closer look at how these methods help keep your pool water clear:

Expert Pool Closing Services

Proper pool closing is the leading preventative measure against green pools come spring. Pool closing involves adding winterizing chemicals, including an algaecide preventative. It also involves draining the lines, using winterizing plugs, and storing your pool equipment in a safe, warm location for the winter.

If that sounds like a big job, it’s because it is! Thankfully, pool professionals are here to handle the job for you.

Most pool companies will offer maintenance programs that include cleaning your pool and balancing the water chemicals. This is a particularly useful service for those who are too busy to do it themselves or want to ensure it’s done properly.

They’ve got the know-how and experience needed to save you from the stress of the job—simply put, they make it easy!

Use a Sturdy Pool Cover

A well-installed, sturdy pool cover will keep algae and other contaminants out of your pool over the winter. From dirt and debris to rain and meltwater, there are a number of contaminants that can contribute to algae growth. If too much debris gets into your pool, it can stain the liner or tiles and make it an algae-friendly environment.

Keep the Pool Cover Clean

Pool maintenance experts recommend that you use professional pool covers as opposed to tarps or other covers that have a weaker structure to ensure the safety of those around the pool. A good alternative to sturdy covers is the mesh safety cover as this is porous and allows water to flow through easily. If you’re planning to install a mesh safety cover, make sure you fill your pool up to 12 inches to the top of the deck. This will avoid damage to the cover.

If you’re opting for an automatic pool cover, fill your pool up to 8 inches from the top of the deck. Since this option doesn’t allow water to flow freely, you’ll need a submersible pool pump to eliminate water from the top.

It’s crucial to clean your pool cover thoroughly and frequently, regardless of whether it’s a mesh safety cover or automatic safety cover. To clean the pool, blow leaves and debris off the cover, and use a hose, soft car brush, and vinyl cleaner – don’t use any other household cleaning products!

Check the Chemical Balance

A drop in chlorine over the winter can lead to algae blooms, especially if you don’t have your pool securely covered. So check the water’s chemical balance every two to three weeks over the winter or until the water freezes and adjust the chemicals as needed. The ideal pH range is 7.2 to 7.6.

Add More Winter Chemicals

Since winterizing chemicals last about five months, consider adding more to your pool water in February or March (or once the ice in your pool starts to melt). These chemicals will help prevent algae growth when the weather starts warming up and the water temperature becomes hospitable to algae.

What Happens to Algae During Winter?

Over the winter, the cold temperature can slow down algae growth. But on a warm day, winter chemicals will become quickly depleted, and more organisms will come to life in your pool water.

If your pool water has contaminants, these organisms, namely algae, will feed off the organic material and start to grow and spread throughout your pool.

How to Deal with a Green Pool When You Open it in Spring

If your pool is green upon pool opening next spring, follow these steps to clean your green pool:

1. Determine the Severity of the Algae Blooms

Depending on the type of algae is growing in your pool, the treatment plan will vary. Determining the type of algae may not always be easy since the colours could be less obvious due to cloudiness. Try to examine the algae as best as you can and look for the following signs:

  • Green algae: This is the most common among the types of algae and luckily, the easiest to kill. Green algae is cloudy and will float to the surface of your pool. All you need is proper filtration and sanitization to eliminate the risk of getting green algae in your pool.
  • Yellow algae: Often resembling pollen or sand in the corner of your pool, yellow algae is rare and not slimy like green algae. It’s also chlorine-resistant making it harder to treat.
  • Black algae: While this form of algae is technically a cyanobacteria, it can still land itself in your pool. It nourishes itself allowing it to grow very quickly and it will root itself into concrete surfaces (like your pool base and surrounding area) making it extremely difficult to treat. Worst of all, if you don’t eradicate this pest and fully destroy the roots, it will grow back.

2. Test the pH Levels

Before you add a shock treatment to clean the algae from your pool, make sure the pH level isn’t high to avoid having very cloudy pool water after shocking the water. The pH level should be 7.2 or lower. If it’s higher than this, add a gallon of muriatic acid.

Make sure the test the pH again after shocking the pool and circulating the water for four hours.

3. Backwash the Filter

Backwash your pool filter. Sand filters should be backwashed for five minutes. Add fresh diatomaceous earth (DE) to your DE filter. Or thoroughly rinse your cartridge filter and install it if it was removed for the winter. Check to make sure it’s in good condition before shocking your pool.

In some cases where the pool water is very green, pool maintenance professionals recommend temporarily removing the filter from the pool to allow the chlorine to kill live algae and bacteria. Once the water turns grey up, you can install the filter again. For sand filters, you’ll need to run the system on “whirlpool” or “recirculate” to remove the algae. It’s also highly recommended to clean the filter often once the pool water is clear.

4. Shock the Pool

To treat an algae-invested pool you’ll need to shock it with calcium hypochlorite. The dose will vary depending on the size of your pool. Follow the instructions on your shocking kit and once you’ve determined the size of your pool compared to the shock levels it needs to meet, multiply that number by two, three, or four depending on the type of algae:

  • Green algae: Shock two times
  • Yellow algae: Shock three times
  • Black algae: Shock four times

It’s important to avoid using stabilized chlorine to shock your pool as you’ll end up with far too much cyanuric acid. Too much of this acid will inhibit sanitizer which can lead to algae growth or other more serious issues. To ensure your pool equipment is sanitized while you’re shocking your pool, keep them in the shallow end of the pool.

Only add an algaecide if the shock does not make your pool water clear or, in rare cases of extremely strong algae.

5. Brush the Pool

It’s recommended to brush the pool immediately after shocking. After your pool water has circulated for 24 hours, it should no longer be green. It might still be cloudy, and you may notice some green areas that will need brushing.

If your pool is still green after 24 hours, then your water might have too much of the wrong chemicals—such as phosphate and cyanuric acid.

It could take a week or longer for the cloudiness to clear. If you have a cartridge filter, you will need to clean it twice a day for at least two days or until the water is clear. And if the cloudiness doesn’t clear with your DE filter, then it may be clogged and will need maintenance.

6. Maintain Your Pool

Keep your pool clean with a reliable chlorinating system, such as an in-line, floater, or saltwater chlorinator system. Also, use a water clarification solution and clean your filter regularly.

  • For DE filters, backwash once a month;
  • For sand filters, backwash every two weeks or check the pressure and backwash once it’s around 5 to 8 psi or higher.
  • For cartridge filters, refer to your manual or verify the pressure and backwash as soon as the pressure is at around 7 to 10 psi or higher. If you’re having low flow with a clean filter, you’ll need to replace it – filters need to be replaced every 2 years or so.

Be Proactive About Other Common Winter Maintenance Issues

Besides green water, other common winter pool issues, such as stains and leaks, can be prevented with proper pool closing and pool maintenance.

Keep your pool protected and clean this winter so that you won’t be stuck with an unpleasant green surprise come spring.

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