Is Your Pool Water Cloudy? Here’s how to fix it [Updated 2023]

How to clear up cloudy pool

These 6 steps will clear cloudy swimming pool water.

Test the water pH
Check your calcium hardness level
Make sure you have good water flow
Clean (or backwash) your pool filter
Check for high phosphates
Shock chlorinate the water if it has not been done recently

Our technician recently visited a green pool that had five times the normal chlorine level and was still green! Why? The pH of the water was so high that the chlorine was prevented from working and so it was not able to clear the pool.

High pH reduces the killing power of chlorine

If the pH of your pool water is high, the effectiveness (or killing power) of pool chlorine is greatly reduced. This may cause the water to appear cloudy. The orange line on the graph shows that when the pH is at 6.5, chlorine is 91% effective. It also shows that when the pH is 8.5, chlorine is only 9% effective. In short, high pH “locks up” chlorine so check the pH regularly!

Low Water flow can cause cloudy water

It is vital that the pump you use is the correct size for your swimming pool. If it’s too small, then there will be insufficient water flow to filter the water properly. If the pump is too large, the strength of the water flowing through the filter can blow the fine sand through the pipework and back into your pool. Also, inadequate filtering time each day may cause cloudiness, even if the pump and filter are the correct sizes. This means that there isn’t enough pumping time for all the water in the pool to be properly filtered and chlorinated.

High Phosphates in pool water

Sometimes, cloudy water has little to do with the size or cleanliness of your pool equipment or filter. Bird droppings, leaves, pollen, and even dirt can play a role in increasing phosphate levels which can lead to cloudy or green water. A quality phosphate remover will remove high phosphates easily. This is because phosphates are the primary food that algae need to survive. Remember, high phosphates create a huge amount of food for algae to thrive on. Therefore, removing phosphates can also work to decrease the chances of your pool turning green. Another challenge of high phosphates is the increase in chlorine consumption. This happens because the increase in organic material in the water consumes the free chlorine faster.

Three solutions for clearing cloudy water problems.

First, a clarifier will gather the water-borne particles together so you can filter them out. This process often clears the water completely.
If the pool water is very cloudy and you can’t see the bottom, try using a flocculent to clear the water. This will gather, or ‘flock’, the organic particles in the water and bring them to the bottom of the pool so you can vacuum them up. Flocs can also remove phosphates as well which also helps.
A fine skimmer basket sock helps trap finer particles before they enter the main filter. Using a skimmer sock will keep your filter clean.

High Calcium Levels in pool water

High calcium hardness levels can lead to cloudy pool water. To check your calcium levels, take a water sample to your local pool shop. They can test your calcium hardness levels for you. According to Australian Standards (1926.3), concrete pools require a calcium hardness level between 80-500 ppm. For fibreglass pools please contact your pool manufacturer to obtain the recommended levels for your pool. High calcium levels also make the water feel ‘hard’ to swim in and also surface issues.

Backwashing a sand filter

You should backwash most sand filters every 2 weeks during winter and every week during summer. This also applies to cartridge filters as well. However, backwashing more frequently than this can lead to excessive sand loss, cloudy water, and poor filtration. Changing the sand in your filter every 7 years can be a great idea. Old sand filters with the original sand inside will often have lumps of solidified sand throughout the filter. This means that any contaminants in the pool water are simply bypassing the lumps of sand and re-entering the pool without any filtration. Clients who change their sand are often amazed at how clear the water is after the change.

How to shock chlorinate a swimming pool

First, start by testing your pool water to make sure the chemistry is in balance. Remember, regular shocking will remove the ‘dead’ chlorine (chloramines) from your pool and kill off most algae growth. These chloramines ‘bind up’ the free chlorine and significantly reduce its effectiveness. Because of this, your pool water can have plenty of chlorine but still be green and stay green.

To shock chlorinate properly, most pools typically need at least 20 litres of liquid chlorine. This should do every 6 months. Your pool shop can help you determine the right amount of chlorine needed to properly shock your pool. Importantly, many pool owners are often surprised by how much chlorine their pool needs to shock chlorinate properly. IN some cases it can be as much as 60 litres at one time!

Shocking at the beginning and the end of the swimming season is a great idea. Finally, shock chlorinating in the late afternoon will help protect the liquid chlorine from the UV light from the sun. This reduced exposure to UV from the sun extends the life of chlorine and increases its killing power. Finally, don’t forget to test and balance the pH of the water before shocking the pool.

dirty sand filter — Old sand filters with the original sand inside which has since partially solidifed

green pool — Pool water can have plenty of chlorine but still be green

How to clear cloudy pool water

The best way to clear cloudy pool water is to run pool pumps and chlorinators for around 4 hours a day in winter and 8 hours a day in summer to keep the water clean and safe. It is common during late Spring, when the weather and water start to warm up, for pool water to turn cloudy. This is because the chlorination system may still be on winter mode (4 hrs per day) when the weather starts to warm up and this can lead to low chlorine levels. Remember that the warming pool water will have low chlorine levels that cause cloudiness in the water.