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Get rid of green pool water

There’s not much more repulsive than going for a swim in green pool water. Pool algae can stick to pool surfaces and even make the water look like a swamp near a chemical waste plant if you’re really unlucky. How do you get rid of this stuff and keep a pool staying clean?

Depending on the severity of the problem, there are a few relatively quick ways to get things back in order. But it often doesn’t stop there. You need a full-on strategy during the warm and sunny months to stop your pool from turning green again.

About Pool Algae

Believe it or not, there are over 21,000 different kinds of algae in Earth’s many bodies of water. The good news is that only 40 or so kinds can grow in swimming pools, including salt water. The bad news is that pool types aren’t your ordinary pond algae. They are tough and growing stronger as they evolve. For example, it’s likely your pool can get greener in the passing seasons as it grows slightly more resistant to low levels of your chlorine  (still the most useful algaecide),  forcing you to increase your treatment amounts more and more. Combined with the rise in phosphates (more food) that can collect in your pool over time from your yard and the air, your battle escalates.

The most familiar form is green in color, but yellow and black (green/blue) varieties can exist too in our backyard water luxuries. Algae is alive, and is no different than any other green plant that uses sunlight, CO2 and H2O to produce it’s nutrients. Along with ample sunlight, give pool algae some warmer temperatures and relatively still waters, and it can thrive.

Cleaning and Preventing  Green Pool Water

Getting rid of green pool water is a process that combines several things. We’ll talk about the most important below. But truly the most important is that all factors to combat (kill and even prevent) green algae be in place. Here are the factors that if you ensure are working on a regular basis will give you peace of mind. Naturally, if any of these could be full time, then you’d have it made, but who wants to swim in ice-cold water?

Algae does best in calmer waters. If you can create turbulence in your pool, it will slow down growth. Since you can’t go swimming 24 hours a day to stir things up, you can at least ensure you’re getting good circulation from your pool’s pump. In the summer, your pump needs to run for 3-4 hours every day to help avoid green pool water, as opposed to just  2 hours every other day in cooler temperatures. This will help disrupt the pool’s stagnant environment, stopping algae’s tiny root systems from taking too strong of a hold on your pool walls.  If you’re faced with an advanced stage of algae blooms and your water is totally green, circulation will only be as good as your filtration system (more on this below).

The ideal turbulence of course is brushing. You’re literally tearing algae out of it’s growth-place–by the roots–and sending it out to die. Of course, again, you need your filter to pull it in and trap it from getting back out into the water where it can concentrate and discolor it to some ugly shade of green.

Brushing can be hard work because you have to scrub large surfaces at awkward angles. While an automatic pool cleaner or vacuum can help, your brush and your arms are your best tools. If it helps, just understand that when you move algae off your plaster, fiberglass or pebble tec, you’re exposing all of it to your chlorine at that point and not just the top layer like it is when attached to the sides of your pool.

Having a good, clean filter is vital to your overall plan to keeping your pool green-free. Make sure it is back-washed regularly, especially after large brushing jobs or running thick green pool water through it. This is the place where these tiny green organisms will be trapped and exposed to your chemicals continuously as water passes through the system.

If your pool is truly a dense color of green, no amount of brushing will fix it. In some cases, super-chlorinating will only do so much too in killing off the thickness of algae. You need to suck up as much as you can. It will be up to your filter to grab the stuff as you run your auto-cleaner or vacuum. Pools with dark green pool water can return to near normal in the matter of a few hours, just by running the water through a clean filter. It may be necessary to backwash or even do a full cleaning of your filter (and re-add D.E. powder if applicable) before the water clears up.

Sanitize (Chlorine)
While there are massive amounts of products available to treat green pools, realize there is no magic formula for algaecide. The key here is not to get fancy. Simply super-chlorinate (add a large quantity of chlorine to your pool at once) and brush well.

More Tips

Green water in a swimming pool

  • If your pool is slimy and slippery, it just means that a protective layer is forming to help keep out chemicals. Get to brushing!
  • In many cases, after brushing your green pool, giving it a shock treatment, and running the filter on over-time for a day you’ll think you’re out of the woods. Unfortunately, you’re not seeing the left-over microscopic spores that are just waiting to reproduce through very rapid cell division and begin turning your pool water green again. Keep at your routine for a few days or more even long after it’s cleared up.
  • Check your pool’s hydraulic system. There may be ways to fine-tune it to help prevent green blooms. For example, install directional fittings to aim return outputs at stairs or corners.
  • If you have a particular bad “green spot” in your pool, it can help to throw chlorine granules directly on it instead of a traditional broadcast out in the water. Then, use your brush to “rub” it in. The temporary rise in pH and higher concentration of sanitizer there will “kill the green” much faster.
  • Similar to the previous point, you can anchor a few chlorine tablets in bad areas to increase the “toxicity” of that spot – this will reduce greeness.
  • It may seem obvious, but it’s important that regular water conditioning be in place such as maintaining a pH level of 7.4-7.6 (may vary depending on your location) and Chlorine levels of 1PPM (parts per million) or up to 3PPM in more troublesome cases.
  • Tried everything, and your pool is still greener than ever? It’s probably time to have the pool completely drained. You can give it a chlorine wash or even an acid wash to completely destroy anything living in your pool.

As with any problem like this that can grow out of control, remember that prevention is the best cure. Stay on top of your circulation, brushing, filtration and water treatments and you’ll avoid your pool water turning green.

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