Why is my pool green? reasons & solutions for fixing green pool water

how to clean a green pool

If you own a pool then chances are you’ve experienced some kind of green pool water at some stage. Generally green pool water is caused by the presence of algae.

But what exactly causes algae to grow in a pool? Finding the reason for the problem can be a tricky task, this can leave you feeling frustrated which can lead to you potentially falling out of love with your pool.

Today we’re going to take a look at the reasons, and solutions you need to know to get rid of that uninviting green pool water, and make it crystal clear again.

Here is a list of reasons we’ll be going over.

  • Poor filtration & circulation
  • Bad pool chemistry

1. green pool Water due to bad pool chemistry

how to clean a green pool fast

If the water in your pool is beginning to turn green the best place to start is by checking your pools chemistry with a pool testing kit. This will give you a good indication of how healthy your pH, and chlorine levels are.

So what do you do if your chemical levels are out? and how do you balance them? Well let’s find out.

How to balance your pH Levels

First of all what even are pH levels? PH levels are a measurement of how acidic or basic (alkaline) the pool water is. This is measured on a scale of 0-14. Anything less than 7 means your water is too acidic, and anything higher means your water is too basic.

Having a balanced pH level in your pool is one of the most crucial aspects for keeping healthy pool water. Ideally you want to keep your pH levels between 7.4 – 7.6. Now the reason keeping a healthy pH level is so important is fact that It plays such an important roll in your pools sanitising system, especially when it comes to the effectiveness of the chlorine.

Essentially as pH levels go up the ability of chlorine to kill germs goes down, potentially resulting in green pool water. Or if your pH levels are too low, the water becomes acidic, which can lead to damaged pipes, or even damage to your filtration system.

Now in order to keep healthy pH levels you must also have your alkalinity levels balance as well. Ideally you want to keep these levels around 100-150 parts per million of alkalinity. Alkalinity works as a buffer to help keep the pH levels stable since they are highly volitile. They tend to mirror each other, if pH levels go down so does the alkalinity, and vice versa.

So how do you balance these levels? If your pH or alkalinity levels are too low then you’re going to need to either add alkalinity increaser, or sodium bicarbonate (baking soda). When doing this make sure you use a chemical dosing chart to ensure you’re adding the right quantities.

If your pH levels are still low after adding the alkalinity increaser you can then add either a pH increaser, or sodium borate which will only bring up pH levels.

One important thing to know when trying to balance your pools chemistry levels is how many gallons of water are in your pool. This will ensure you’re adding the correct amount of chemicals, which in return will give you the best results.

How to balance your Chlorine levels

First of all you’ll need to check your pools chlorine levels. The best way to do this is to use a pool chemical test kit. A healthy chlorine level should be between 1-3 parts per million. When you’re testing the chlorine you’re checking to see how much chlorine is active, and killing bacteria.

If your chlorine levels are too high the are a few different methods you can try to help reduce these levels. The first thing you can try Is using a pool grade hydrogen peroxide, this reacts with the chlorine which in return creates extra water and oxygen that helps water down the existing chlorine. This method works best if you’ve got a pH level of 7.0 or higher.

The quickest and easiest way to lower your chlorine levels is by using a chlorine neutralizer, a good choice is sodium bisulphate. If you choose this option remember that it’s easy to overdo it, so start with adding small amounts first. This will also significantly lower your pH levels so you may also need to use a pH booster afterwards.

Or you could try the natural way, which just involves that good old yellow ball in the sky. A few hours of direct sun sunlight has the ability to reduce chlorine levels up to 90%. This way is great because not only does it require the need of no chemicals, it’s also free. However if you use Cyanuric Acid to stabilise your chlorine levels then you might not have much success as this prevents the sun from braking it down.

So what do you do if you’ve managed to balance the chemicals in your pool, but the water is still turning green? This may means it’s time to take a look at your pool’s filtration system.

Green pool water due to poor circulation

pool water green and cloudy

Having your pool’s circulation running effectively is a crucial aspect to ensure your pool water stays clean and healthy. But before you able to diagnose an issue, first you need to know how your pools circulation system works.

how a pools Circulation system works

A pool circulation system works by drawing water through the pools skimmer and drains by a centrifugal pump. The water passes through the skimmer basket which removes large debris before it gets to the pump’s impeller. The pressure created by the pump’s impeller forces the water through a filter which intercepts any debris not caught by the baskets. In some cases, the filtered water is treated and heated before it is returned to the pool. This system of collection, treatment, and return of pool water is repeated over and over to ensure the water is clean, pleasant, and safe for your family and guests.

now let’s check out the individual parts of the pools circulation pump, and what they do.

  • Skimmer – this creates surface tension, drawing water to the pool plumbing system to intercept & remove debris
  • Pump – Circulates the water
  • Main Drain – Provides pool water to the pump & improves water circulation within the pool
  • Filter – Stops dirt from entering the pool
  • Chlorinator, Chlorine, generator, sanitiser – These are responsible for treating the filtered water before it enters the pool
  • Returns – sends filtered, treated, and heated water back to the pool

Now that you know how a pool circulation system works, you can now being to diagnose the individual parts to see if there’s an issue.

Common reasons your circulation system may be failing

Skimmer Basket needs to be Emptied

If you feel like there’s an issue with your pools circulation system, then a good place to start is with your pools skimmer. If your skimmer basket is full of leaves and sticks then this will prevent water from making it to your pools pump.

Ideally you should be emptying your skimmer basket at least once a week so the debris doesn’t have time to brake down. You’ll know your skimmer has a blockage if your pool pump is either pulsing, loud, or the pressure is low.

problem with the pool pump

If the waters pulsing or surging in your pump, this might be a sign there’s a blocked pipe. But before you check this it’s best to rule out other problems first like a potential air leak. You’ll also need to check the o-ring on the pump lid, and check the impeller inside the pump isn’t clogged.

If your water intake into your pump is slow, even with the skimmer basket being empty, then it may be due to the skimmer weir (door) being stuck. In order to ensure the door operates correctly its best to have your pools water level halfway up the skimmer. If the skimmer weir, and water level looks good it may mean you have a clog in your skimmer line.

To remove a clog in the skimmer line first you’ll need to cut the power to the pools pump. Next open up the clogged skimmer line and shut off all other intakes. It’s important to remember that the only line that should be open is the blocked one. Next remove the pumps lid, and insert a hose down into the port. You’ll need to ensure there is a tight seal or else water will spray out from the port, instead of being forced down the line.

This should hopefully result in whatever’s stuck in you skimmer line to be flushed out.

why is my pool green after a shock?

First of all, don’t panic if your pool turns green after a shock. There are a few different reason this can occur. Your pools water can immediately turn green after a shock if your pool’s water has metals present in it like copper. These metals oxidise when exposed to high levels of chlorine, which results in your water turning green. To prevent this from happening you can use a pool metal remover beforehand.

Another reason your pool may still be green after a shock might be due to the fact that your pool still has a high level of phosphate. Water with a high phosphate levels can be be the perfect breading ground for bacteria resulting in an algae outbreak. There are four main sources phosphate can accumulate from. These are human sweat, skin and hair products, and detergents used to wash your swimwear.

If high phosphate levels are the cause of your green pool water then you’ll need to use a phosphate remover. Doing this should hopefully create an uninhabitable environment for the algae, essentially killing it.

Hopefully this have given you the information, and knowledge you need to finally get rid of that horrible green pool water, and make it sparking clean again.

If you’re looking for reasons or solutions for cloudy pool water then feel free to take a look at our full troubleshooting guide here.

The Morris's

The Morris's

Hey, we're Lana and Cam the creators of this site. We love to spend time together as a family, and time in our pool. We're here to bring you the best info on pool care, pool cleaners, and other great pool related products.

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