What Causes Cloudy Pool Water?

What could be worse for a pool owner than cloudy water in a pool? Is it familiar to you when you wake up one morning to find pool water has suddenly turned dull and cloudy? Don’t worry. It's a surprisingly common occurrence that is caused by a number of factors, which sometimes makes it tricky to detect and treat.

To put it simply, the term “cloudy” is used to describe water that looks milky or has a murky, unsightly appearance. This is due to tiny particles in large numbers reflecting back the sunlight. These particles are so small ranging from 0.5 to 5.0 microns that they’re virtually impossible to see.

And much like any other pool issue that you might have encountered before, it’s better to identify the root cause of the problem first before working on a solution.

Pool experts have agreed that most of the time cloudy pools are caused by seven main issues:


1. The Environment

Everything around your pool can cause your water to be cloudy, that includes: weather, birds, construction, trees, gardens, the sun, people, and pool algae.


2. Improper levels of chlorine

Chlorine kills off bacteria, viruses, and micro-organisms that can cause your pool water to become opaque. The suggested amount of free chlorine is between 2.0 and 4.0 parts per million (ppm). You must remember that chlorine levels can be affected by the sun and any organic waste such as your sweat or sunscreen.

When there is an imbalance in your pool’s pH level, it makes the free chlorine ineffective. This imbalance cause chloramine to form and when combined with chlorine result in a cloudy pool water. A pool’s pH level should be kept between 7.2 to 7.8.


3. High total alkalinity

Pool water with a high total alkalinity (TA) is often associated with cloudiness. This is because it can cause an imbalance in the pH levels and lead to calcium scaling. Typically if your TA is higher than 200 ppm, you’re at risk of a cloudy pool and just like imbalanced pH levels, your chlorine will be less effective.


4. Very high calcium hardness (CH) levels

Water with high amounts of calcium in it can also cause cloudy water, however, low calcium levels may cause corrosion and damage your pool structure and equipment. It’s best to maintain the calcium hardness in your pool at 150 to 400 ppm.


5. Debris

Environmental debris such as leaves, twigs and flowers can affect your pool’s water quality particularly if your pool water circulation isn’t optimal. Even the smallest debris such as pollen, dust and bird droppings will impact the appearance and can build up in your filter.


6. Rainwater

If you’ve recently experienced a heavy storm and your pool water is cloudy, that’s likely to be the main cause. This is because rainwater can cause nitrates, phosphates and other chemicals to run-off into your pool. Heavy rainfall will also dilute your chlorine levels rendering it less effective.


7. Clogged filter

When the filter is not running or clogged, water becomes stagnant and may cause debris to build up, making your pool water look murky. In fact, problems with your pool’s circulation system are the leading cause of cloudy pool water.

You also need to check for your filter media if it needs to be replaced or cleaned. Sand filters need their sand to be replaced every 5 to 7 years. Meanwhile, cartridge filters need filter replacement every 3 to 5 years. Diatomaceous earth filters, similar to sand filters, need to be backwashed every month and you must replace the wasted D.E. with new ones.

Always remember that when your pool filter system can’t remove contaminants, you are left with cloudy pool water, and probably a handful of other pool problems.


8. Human causes

Excess particles that gather during swimming could be the cause of your cloudy water. Sunscreens and oils are the most common particles found in swimming pools as well as make-up, perspiration, body oils and bodily fluids. These reflect back the light and result in the appearance of a cloudy pool.


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