Why is My Salt Water Pool Green and How to Fix It in 10 Steps

A green salt water pool is nothing you want in your garden. But why the pool turns green, and how to fix it?

To clean a green salt water pool, you have to increase the salt content to 3000 ppm and scrub the pool with a brush. If necessary, a pool shock or an algaecide must be used.

Has the water in your salt water swimming pool turned green? This guide will teach you how to clean a pool without draining the water.

How to fix a green salt water pool?

You can fix a green salt water pool relatively quick.

Follow these steps to fix a green salt water swimming pool:

  1. First, clean out your filter (it should be done every 10 to 14 days).
  2. Check the salt level. If it’s less than 3000ppm, top up the water with fresh salt water.
  3. Keep adding salt to obtain a salt level of at least 3000 ppm (parts per million).
  4. If you like, add some algaecide agents to improve the maintenance.
  5. Run the pool pump and scrub your entire pool with a brush to loosen the algae.
  6. Then adjust the pH value to 7.2-7.6 using pH increaser or pH decreaser.
  7. If the pool is not green after this, you can carry on as usual. If it is still green, continue with step 6.
  8. Use a pool shock to over-chlorinate the swimming pool. With this, you can kill all algae in the water.
  9. Let the pool pump run for 24 hours and use a flocculant to improve the filtration.
  10. Afterward, check the chlorine level. If it is still above 1.5 ppm, let the filter run another 12 hours.

Maintaining a green salt water pool is crucial to keep an eye on the chlorine level. This should not be below 1 ppm (part per million).

Why is the salt water pool green?

I have already addressed how to fix a green pool but have never explicitly addressed why a salt water pool turns green.

First and foremost, the pool will turn green when green algae multiply in the pool.

This can happen even with proper water treatment and a good pH level of the pool water.

Most of the time, the pool water tips over after a thunderstorm or when the air is humid. It is not uncommon for the pool water to be green after just one day – you have no direct influence here.

But what you can influence is the filtration time of the pump.

Beginners often want to save electricity costs and run the pool pump too short.

If I were to answer why the salt water pool turns green, it would be that the pump in the pool is running too short.

Increase the circulation times in the pool and scrub the pool on the dead zones, then the pool should not turn green.

Another reason why the pool turns green is that the disinfectants are not working properly due to improper use.

During this time, the pool water remains clear but slowly and unnoticedly turns green.

When do green algae multiply the most?

As already mentioned, the green algae multiply most strongly in warm and humid temperatures.

But poor water values can also turn your salt water pool into a green monster overnight.

It is wrongly assumed that the algae do not multiply at low temperatures in winter, but this is not true.

Algae also grow at low temperatures, just much more slowly.

That is why an algaecide should be applied to the pool when you make it ready for the winter.

Well water turns the salt water pool green

I have often heard pool owners complain that the pool has turned green after filling the salt water pool with well water.

This may be because the well water is rich in iron. In addition, the well water is an ideal breeding ground for green algae.

If you fill the pool with water from the well, you should prepare the water accordingly; otherwise, you have to expect green pool water.

Inadequate water quality from supplier

If you have a supplier fill your pool with pool water for the new bathing season, you should definitely measure the water values ​​beforehand.

Some providers fail to deliver clean pool water. It is not uncommon for the water supplied to contain dangerous black algae.

You can easily avoid green pool water by checking the water values ​​before filling.

If your salt water pool turns green anyway, you now know how to get it clean.

FAQ about cleaning a green salt water pool

If the salt water pool is green, your bathing fun can be saved with these simple measures.

But what should you do if you are unsuccessful despite following my instructions?

To that end, I’ve answered the reader’s most common questions about the green salt water pool.

The salt water pool is green despite the good water values

There can be many reasons if the salt water pool is still green despite good water balance.

One of the most obvious reasons is not regularly scrubbing the pool with the pool brush.

My procedure against green pool water is of little use if the algae are not loosened and filtered out.

The green algae may have nested under challenging places in the pool or even in the filter system and continue to spread in the pool.

But one of the most likely reasons is that the filter run time is low, and there are dead zones in the pool.

Check the filter run times and determine whether the pool pump is acceptable for your pool size – you will find a complete pool pump guide on my blog.

It is also not unlikely that you are using a flawed water tester, and the values ​​are misread.

An electronic water tester can be used to precisely determine the water quality.

Use vitamin C in green pool water?

Unlike on YouTube or other guides, I strongly advise against using vitamin C in green pool water.

The pool’s vitamin C (ascorbic acid) is not a miracle cure and only has a purely cosmetic effect.

Yes, the cloudy pool water may become clear quickly, but all the cloudy substances are still in the pool and have not been filtered out by vitamin C.

Furthermore, vitamin C is a food source for bacteria and can lead to even greater pool water cloudiness.

If you wonder why vitamin C does not help or at least only helps for a short time, then that is simply because it has no real effect in the pool water.

Do Home Remedies Help With Green Pool Water?

If the pool water is green, inexperienced pool owners use household remedies to get the pool clean again.

From my experience, I can only advise against using most home remedies for pool maintenance.

Even if you can clear the green pool to a certain extent, the success will be short-lived in most cases.

Use only certified products for the pool maintenance, and you will have permanently clean water in your salt water pool without any problems.

Can you swim in the green salt water pool?

A common question from pool owners is: Are green algae in the pool dangerous for people, and can you swim in green water?

You can theoretically swim in green pool water without taking any health risks, but I would strongly advise against it.

But the question is, when is the green color of the water too green for a swim?

The green algae are not as dangerous for your own health as the dreaded blue algae but can be harmful from a certain point in time.

One danger from green algae is that they are slippery. That is why you should clean the pool beforehand before going back into the pool.

But how long can you wait to clean the pool and leave the green water in the pool?

The point at which green algae can be harmful to your health is when it starts to rot, creating gases that are inhaled.

Then, the time has come to clean the green pool.

When does the green pool water have to be completely drained?

The water in the pool can generally remain for 1 to 2 years and be reprocessed for the coming bathing season – but this always depends.

Did you use antifreeze, or is the pool completely overgrown with algae after the winter?

I recommend draining the pool water and cleaning the pool accordingly in both cases.

Spring is the best time to do a complete water change in the pool anyway.

How to clean your pool after winter is explained in detail in my blog under the link.

In most cases, it is unnecessary to pump out all the pool water and fill it up again.

But if a pool stands for a long time without water treatment, it comes to digestion and gas formation in the pool. A complete water change and thorough cleaning are necessary from this point on.

What can be done to prevent algae growth in the pool?

Cleaning a green salt water pool is one thing, but preventive measures against green algae are another.

This chapter will tell you the necessary precautions to avoid green pool water.

After, it should rarely happen that there are green deposits on the bottom of your pool.

  • Increase Pump Circulation Time: The best measure to prevent green pool water is increasing the circulation time. A rule of thumb is that the water should be circulated for 6 to 8 hours a day. In practice, try to keep the running time as high as possible and extend it if necessary.
  • A flocculant helps against green pool water: The algae may be sucked in by the pump but not filtered. With the use of the flocculant, the filter performance can be increased considerably.
  • Scrubbing the Pool Regularly: The pool brush is still one of the best tools for pool maintenance. Scrub the surfaces in the pool regularly and don’t give the algae a chance to settle in.
  • Use an algaecide against green algae: The algae agent is used to actively combat green algae but can also be used as a preventive agent. Just don’t use too much of it as it can discolor your hair and nails.
  • Produce free chlorine with the floater: Chlorine is your best friend in the fight against green pool water. A floater is ideal for permanently producing free chlorine with chlorine tablets. The chlorine value is difficult to set exactly, but at least it works better with a metering float.
  • Use pool cleaners that contain silver: Silver has a disinfectant effect and is well suited for pool maintenance. Under certain circumstances, a silver-based agent can prevent the green pool. The disadvantage is that these funds are unfortunately offered far too rarely.

Do you have any further questions about the green salt water pool?

Write me a message with your question at @contactswimfool on Twitter or Facebook – I’ll be happy to help.

Happy swimming!

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Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

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