Is Green Pool Water Safe for Swimming?

green pool water

We’ve all seen a swimming pool that looks a little less than inviting — clumps of leaves, settled dirt in the deep end, and, in some cases, green water. Let’s get to the bottom of what causes green water and how it can affect your pool.

Why Is My Pool Water Green? The Causes of a Swimming Pool Turning Green

Pools require a certain level of maintenance in order to stay clean and provide enjoyment for the whole family. If your pool has lost its signature crystal clear color and is turning green, there could be a number of causes, including algae, pollen, metal, low chlorine levels, high pH levels, and broken parts.

Algae Overgrowth

The most common cause of a green pool is green algae. Algae are single-celled plants that settle in warm areas where they can get all the sun and nutrients they need. Once algae have named your pool their new home, they will grow and spread very quickly on the walls and stairs of your pool.

Pollen and Metals

Another green water culprit could be pollen. Pollen is a green-yellow color and can easily be carried in on the wind, land in your pool, and make it appear green.

Your pool pump, ladder, heater, copper-based algaecides, and other metal components also have the ability to turn the water green due to their reaction to pool chemicals.

Low Free Chlorine Levels

We use chlorine to keep our pools sanitized and free of any harmful organisms. If your chlorine levels are too low, you run the risk of these organisms, including algae, taking over.

High pH Levels

A pH reading allows you to measure the level of acidity in your pool. Too high of a number, and the chlorine won’t be able to fight off unwanted organisms. This can often be fixed with a pH-reducing product like sodium bisulfate.

Broken Filter or Filter Not Running Long Enough

Your filter is responsible for filtering out dirt and debris and leaving you with cleaner water. If your pool begins to look cloudy or green, you may not be running your filter long enough. If the problem persists, there might be something wrong with your filter.

Is It Safe to Swim in Green Pool Water?

There’s nothing worse for a pool owner than looking forward to taking a dip all day just to find that your pool water has turned green and looks unswimmable. No matter how badly you’d like to cool off, if your pool water is green due to algae growth, you may want to reconsider diving in.

Green algae welcome the growth of bacteria like E.Coli. By choosing to swim in a pool with algae, you run the risk of developing a rash, infection, or illness.

We highly recommend contacting a professional and taking care of your green water woes before entering your pool.

How to Clean a Green Pool

A pool requires a good balance of chemicals to stay clean. So, in order to restore that green water to its former glory, you need to get the chemicals back to their ideal ranges. This process may get a little repetitive at times, but the results will be worth it!

For an in-depth look at the different kinds of pool algae and how to get rid of them, check out our blog: Pool Algae and How to Kill Any Type and/or Color

Check Your Pool Water Levels

Start by testing your pool water. Take a look at the chlorine, stabilizer, and pH levels and see if they are evenly balanced. If not, balance them!

Turn On Pool Pump and Keep Running

Next, turn on your pool pump and leave it running. Circulation is important for a clean and healthy pool, and your pump will keep everything flowing as it filters your water.

Clean Your Pool Filter

As your pool is green and murky, your filter most likely is as well. Remove and clean it well, replacing the cartridges and backwashing if necessary.

Remove Large and Visible Debris in Your Pool

Big sticks, leaves, pool toys, and any other large objects should be removed from your pool before you get into the next few steps: deep cleaning.

Brush Your Pool Walls and Flooring

Using a stiff, stainless steel brush (or a nylon brush for pools with fiberglass or vinyl liners), brush your pool. This will loosen up any algae that have grown on the wall, floors, and steps, allowing them to be taken in by the filter.

Shock Your Pool

The shocking process involves adding chemicals to the pool in an effort to raise the chlorine levels and kill algae and bacteria. Read the instructions on your shocking product and give your pool double the recommended dosage.

Test Your Pool Water Again

Now that you’ve killed the algae, it’s time to test your pool water again. Adjust accordingly until your levels fall within these ranges:

  • Chlorine: 1.0-3.0 PPM (parts per million)
  • pH: 7.2-7.8 PPM
  • Total Alkalinity: 80-120 PPM
  • Calcium hardness: 200-400 PPM

Add Algaecide

For a final chemical shock, you’re going to add algaecide to your pool. Algaecide contains additional chemicals that eliminate any lingering algae that the shock may have missed.

Brush Your Pool Again

Take out your brush and go over your pool once again, taking extra care to reach every corner. This will free up any remaining bits of algae and send them toward the filter.

Vacuum or Backwash Your Pool

Vacuum away any settled debris on the floors and walls of your pool. For an added layer of cleanliness, turn your filter settings backward. This reverse in flow is called backwashing and helps dislodge any stuck debris from your filter.

Run Your Pool Filter

Keep your pool filter running! Let it collect all the remaining dead algae, as well as any other contaminants, and you’re one step closer to swimming again.

Clean Your Pool Filter Again

After bringing in all that yuckiness, your filter will need another good clean. Thoroughly clean or backwash it, once again replacing cartridges if need be, and place it back in its place to continue working.

Preventing Green Algae in Your Swimming Pool From Happening Again

A well-maintained pool is a clean pool! Avoid having to repeat all of these steps again in the future by keeping up with your pool chores as much as possible. Keep your water levels balanced, run the pump, add chemicals as needed, and clean your filter.


If you’re dealing with green pool water, it’s best to put the swimming on pause and consult with a professional before taking action. Remember, you never have to deal with pool troubles all on your own! If at any point your green water problems return, give ASP - America's Swimming Pool Company a call, and our team will be happy to help.

Disclosure: While basic pool care is encouraged for swimming pool owners, it is highly recommended you consult with a professional pool service like ASP - America's Swimming Pool Company for any issues like pool algae that arise.