Cloudy Water Causes & Cures

Why do you have it & what causes it:

There is NO SINGLE CAUSE of cloudy pool water.  Cloudy pool water is caused by the following conditions:

Early  algae growth caused by low or inadequate sanitizer/oxidizer levels.

Insufficient filtration caused by too small a filter (sized improperly,  especially true with cartridge filters) or insufficient hours of filter operation.

Too frequent backwashing or  cleaning of the filter (doesn't allow filter to "reset itself" or  collect enough debris which actually aids in filtration).

Poor circulation due to inadequate pump (horse power doesn't mean too much, sometimes smaller is better) or positioning of the return jets.

Poor circulation in your swimming pool due to lack of usage.

Overwhelming introduction of dirt & debris into the pool (overhanging trees, construction area nearby, etc.)

Heavy bather usage without proper additions of sanitizers/oxidizers.

Overwhelming introduction of "unfilterable" waste from swimmers (cosmetics, lotions, body fluids).

Use of Heater (water too warm) causing faster sanitizer usage.

Use of Solar Heating System (system is not being adequately chemically treated to kill build-up of biofilms, algae, etc.).

Biofilms in the filter system - filter tank, pump, plumbing lines.   (more information on biofilms here)

 ...Are you getting the Hint?  Here's more...

Insufficient sunlight on the pool.  UV rays are a GREAT natural oxidizer. (Indoor pools are a whole other  issue that we will not address here,   click here.)

Lawn & chemical sprays "drifting" into the pool (from a neighbor).

HIGH pH causing sanitizer (chlorine) to work more slowly thereby allowing algae & bacteria to grow.

HIGH pH causing scaling to begin to occur.

HIGH Calcium Hardness causing  scaling to occur. HIGH Calcium Hardness is due to regular usage of  calcium-based chlorine (Calcium Hypochlorite such as hth, Sun, many  others) or source water high in calcium hardness (over 300 ppm).   

HIGH Calcium Hardness in  conjunction with WARMER water temperature (over 85°) causing calcium to  precipitate out (calcium dissolves & stays in solution BEST in  cooler water) & cloud the pool.

Filter needing a chemical cleaning (remember that using a straight acid will only set the greases & oils into the filter media).

Pool not being vacuumed or brushed on a regular basis.

Trace heavy metals (iron, copper, manganese) present in the water.

Household cleaners and chemicals being used in or around the pool.

Broken or otherwise damaged filter lateral (sand), septum (DE) or element (cartridge).

Unclean solar blanket.  A biofilm is building on the side in contact with the water.

Make-up water added to pool from an unclean garden hose.

Dirty pool toys & floats putting a strain on the sanitizer.

Make up water that isn't treated the way it used to be.  Many municipalities are treating the drinking water with chloramines rather than chlorine; they do an adequate job with bacteria but don't  have the oxidizing strength to combat other non-lethal pathogens. The switch was done to placate people's perceived "fear" of chlorine being  in the water.

Lack of pool-owner care as in regular testing, vacuuming & maintenance. Your supplier of "discount" pool supplies only want to sell you stuff, not solve your problem.

When was the pool last  shocked?  Hmm?


3 General Reasons for Cloudy Pool Water

Yes! It's easy to understand

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. They  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 - like the pool in the picture above.   
  • 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 back-washed 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. 

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!


Chemical Reasons 

Many pool owners quickly blame "bad chemicals" so let's end there. Here are  some of the factors and their contribution to the cloudy water problem. Water  chemistry can contribute to cloudy or hazy water - if the pH is HIGH (over 7.8)  and / or the Total Alkalinity (TA) is HIGH (over 175 ppm) and / or the Calcium  Hardness (CH) is HIGH (over 350 ppm). 

With pH & TA being high the water will become dull or  flat and the chlorine reacts more slowly and therefore loses its ability to kill  and control bacteria and algae. Now you have early algae growth - another cause  of cloudy pool water. 

High CH doesn't become a problem until the water warms  up to over 85 degrees F. At that point you have a "cloudy" condition that won't go away.  The reason: calcium is one of those minerals that dissolves better in cold or  cooler water as opposed to warm or hot water (at higher temperatures, this can  lead to scaling of surfaces and equipment). Maintain good pool water balance  with these parameters: pH - 7.2 - 7.6 (all pools); Total Alkalinity - 80 - 120  ppm (concrete) or 120 - 150 ppm (vinyl liner); Calcium Hardness 200 - 300 ppm  (concrete) or 175 - 250 ppm (vinyl).

Other chemical or chemistry based reasons for cloudy pool water would be lack of  regular shocking, periodic (about every 6 - 8 weeks) chemical cleaning of the  filter, poorly maintained sanitizer levels, lack of a chemical maintenance  routine. 

Regular weekly or biweekly shocking of the pool aids in  oxidizing un-filterable swimmer waste such as body oils, lotions, urine, hair  gel, perspiration, etc. We find that the single biggest mistake customers make  in their normal care is not shocking the pool often enough or insufficiently  (not using the proper amount of pool shock). 

Proper shocking also helps to "rejuvenate" the chlorine  level and knock out early algae growth. Whenever you have a pool party with lots  of expected bathers, consider shocking the pool the day before (helps build up  the chlorine level providing a buffer for an eventual chlorine demand) as well  as immediately following the party (shocks & oxidizes everything that was  brought into the pool during the party -- if your guests weren't using the  bathroom, the beer & soda had to go somewhere). Using a calcium hypochlorite  shock such as BioGuard Burn Out is preferred since the product will get in, do  its work, then get out. Potassium monopersulfate shocks like Oxysheen work well  to help break up chloramines (combined chlorines), but shouldn't be used  exclusively.

Adding a Natural Enzyme such as ActivNzyme helps to consume and naturally breakdown  greases, oils and proteins that accumulate in the water due to bathers or the  environment.

Final Notes

As you can see there are no 1 or 2 simple reasons for cloudy pool water. It's usually a  combination of factors. Some of them don't even coming from the pool itself. 

The  best solution to cloudy pool water is prevention utilizing a good, regular  chemical and cleaning maintenance program. About 30 to 60 minutes per week is  all that it takes. If or when your pool water turns cloudy, don't start adding  clarifiers or flocs. Get down to the real cause. Look at all of the contributing  factors.


Treating Cloudy Pool Water


Run the Filter System

Your pool's filter system MUST run 8 to 12 hours everyday. Period! The best looking & maintained pools are those where the filter never shuts down. To save money, make sure to use a Timer so that you don't forget. Better yet, upgrade to the modern Variable Speed pumps...this upgrade will pay for itself quickly.

Shock the Pool Water

Your pool water accumulates all kinds of waste that need to be shocked or oxidized. Shock properly (the correct amount) & regularly (every week or 2 weeks) from pool opening to pool closing.

Maintain good water balance

Proper pH, Total Alkalinity & Calcium Hardness levels make a difference in water clarity but more importantly in swimmer comfort and equipment life. Just because the water is clear, doesn't make safe or balanced.

Don't over use "water clarifiers"

In fact, I discourage the use of clarifiers because they often mask a problem by treating a symptom rather than treating a root cause. Adding too much Clarifier will actually result in more cloudy water.

Use natural enzymes

Natural enzyme products like our proprietary, super concentrated ActivNzyme naturally break down all kinds of pool waste, keeping the water clearer, cleaner and feeling softer and nicer.

CHEMICALLY clean the filter

A clean filter does a better job. A clean filter provides longer filter runs and lessens water loss due to excessive backwashing (only when absolutely necessary). Be sure to CHEMICALLY clean the filter every 2 months and especially after treating for a bad algae, slime or mold problem. Your filter does so much of the work for you, treat it well.