Is It Safe to Swim in Green Pool Water?

Reviewed by Andrada Simion, Master of Science in Chemistry

Normally, pool water should be clear, but you may have noticed yours has turned green. Why is that, and is it okay to swim in it? Here’s some things you should know about green water:

  1. It’s Mainly Caused By Algae
    When your pool doesn’t have enough chlorine in it, algae starts to grow and turns your water green. If you don’t add in more chlorine immediately, this can happen within a day, especially if it’s hot out.
  2. Pollen Can Be An Issue Too
    If you have a lot of plants or trees nearby, pollen will be blown into your pool by the wind and settle on the liner. Once enough builds up, it eventually turns your water green.
  3. It’s Possible For Metals To Do This As Well
    If there are metals in your source water, or if they’re introduced to it by cheap algaecides, they will oxidize when shock treating your pool. This will end up turning the water green. Water that’s too acidic due to copper from a heater can also cause this to happen.
  4. Each Cause Possesses Different Characteristics You Can See
    When trying to determine exactly what’s causing this problem in your pool, it’s possible to do so just by looking at it. Algae grows on the walls and bottom of the pool first before sticking to the surface and is a darker shade of green. Pollen sticks to the bottom, but not the surface, and can be more yellowish. Metals will turn the water light green.
  5. You Shouldn’t Swim In It If It’s Caused By Algae
    Algae itself isn’t dangerous, but if the conditions of the water allow it to grow, that means harmful bacteria, viruses, and other pathogens are also able to survive in it. Swallowing this water could get you sick, and if you have any cuts or wounds on your body, they might get infected. Algae is also very slippery, increasing the chances of slipping and injuring yourself.
  6. If It’s Green From Pollen, It’s Completely Safe
    Pollen is completely harmless in your pool and is safe to swim in. Other than being a bit of a nuisance to clean, you won’t feel any ill-effects from allowing it to collect in the water.
  7. You Can Swim In It If Oxidized Metals Is The Cause
    While it’s technically safe to swim in, when your water is filled with oxidized metals, it can stain your hair and clothing. It might be better to avoid using the pool until the problem is cleared up, unless you don’t mind having green hair.
  8. It’s Simple Enough To Clean Algae
    Brush the entire surface of the pool first, and then add in chlorine shock and algaecide. Run your pump for 24 hours in order to circulate the chemicals and get rid of the dead algae. Once the water’s clear, remember to keep it that way by practicing proper pool maintenance.
  9. Cleaning Out Pollen Is A Bit Tougher
    Start by running your filter to get out as much of the pollen as possible, but this won’t get rid of all of it. Use a skimmer to try to remove whatever remains. You’ll need to do this every day to prevent another build up so your water stays clear.
  10. Figure Out Why There Are Metals In Your Water
    Use a sequestering agent to remove the oxidized metals, but they’ll just return if you don’t figure out where they came from. Once you’ve done that, replace whatever is causing it to fix the problem for good.
  11. Keep On Top of Your Pool Maintenance To Prevent It From Happening
    If you test and balance your water quality frequently and do routine cleanings, you won’t have to worry about whether you can swim in a green pool or not. It’ll always be fresh and clear, and you’ll be comfortable knowing that you can jump in anytime you want.