Cloudy pool water is caused by many factors. These factors may be chemical (water balance, pH, improper methods), mechanical (pool filter system) or environmental (source water, excessive rain, heavy use).

Most times, pool owners attempt to treat the symptoms but not the cause of the cloudy water, so we have to look at all of the things that may contribute to the problem. People tend to go immediately to the chemical causes which are NOT there, and neglect the environmental or mechanical  factors.

Let's look at the causes of cloudy swimming pool water, then we can look at treatments and cures.

Before we dive in let's first put cloudy water to the test. Cloudy pool water is in the eyes of the beholder. Cloudy can mean: Dull - the pool water just doesn't sparkle (many people think this is how their pool is supposed to look). Hazy - it just isn't as clear as it normally is. Cloudy - you can make out the bottom of the pool if you look hard. Opaque - the term says it all!

Environmental Reasons

Remember that whatever is out in the world, will eventually get in the pool and detract from water clarity. Pollen, dust, dirt, leaves, make-up water, bird droppings (forgot about those, right?), rain, local construction sites, etc. can all affect your swimming pool. Each of these culprits needs to treated differently. Pollen, dust and other fine particulate can be treated using a water clarifier like BioGuard Polysheen Blue. Flocculants work well in severe situations by settling the particles to pool bottom and vacuuming it all out on Waste. Use a skimmer sock inside of the skimmer to remove fine pollen or dust that may be too fine for your sand filter.

We would also include biofilms as a cause of cloudy water. Although biofilms are already in the pool, they need to be removed and prevented from building. We classify biofilms as an Environmental reason just because they are there. Biofilms are part of the environment. Remove biofilms and solve a myriad of problems.

Leaves, swimmers, makeup water, droppings will create a chlorine demand. Shocking the pool is necessary. Make-up water can change the water chemistry affecting the pH, TA and CH not to mention the possible addition of heavy metals, all of which can cause or add to water cloudiness.

Mechanical Reasons

If the chemistry is good and the pool is being properly shocked and algaecide added every 1 to 2 weeks, then it is necessary to look at the mechanical reasons. The mechanical components contributing to cloudy pool water would be improper filter size (too small), improper pump and motor size (too small or too large a horsepower pump), insufficient filtering time, poor circulation, improper maintenance (vacuuming & brushing). I can recount story after story when I've walked into a customer's backyard to help them troubleshoot a problem pool only to find the filter shut off or improperly connected. When simple corrections are made, the pool water is clear in as little as 24 hours. Let's examine some basics.

Your swimming pool's filtering system should be operating a minimum of 8 to 10 hours per day, every day from opening to closing. If the pool water becomes cloudy or other problems become evident, then constant running of the filter until the problem is solved is required. If the filter was properly sized (even slightly bigger is better) then 8 to 10 hours daily is good. On the other hand, too large of a pump may be "harmful" to the filtration. If the horsepower is too great, you may be blowing dirt and everything else you want filtered right through the filter (especially sand filters). When it comes to 2 speed pumps, make sure the "high" speed run time is set for a minimum of 6 hours daily PLUS and additional 12 to 18 hours at "low" speed).

Consider using an automatic pool cleaner. You'll end up with better circulation, cleaner pool surfaces and less work.

The other mechanical reasons are also important. Regular vacuuming and brushing help with the overall circulation by moving water around. Keep directional "eyeballs" pointed DOWN to force filtered water down to the bottom of the pool and therefore aid in water movement by breaking up dead spots. Too frequent backwashing of the filter doesn't give the filter media enough time to do its best cleaning -- a dirty filter filters a finer particle.

When was the last time the filter was chemically cleaned? Not just backwashed or rinsed, but chemically cleaned.

How about the pump? Are bits & pieces of debris clogging the veins of the impeller? If so, that can dramatically affect the efficiency of the pump and the overall circulation of the pool. Here's an extra look...

One final mechanical reason for cloudy pool water, lack of use. Actively used pools are always better circulated and filtered. So even if the water is cloudy (as long as the water is in good chemical balance), use the pool!

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*Follow the instructions given by your pool care specialist EXPLICITLY. Failure to do so could result in harm to you and/or your pool & its components.

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