Cloudy pool water is a very common problem for pool owners. But it doesn’t have to be your problem.
Have you got up in the morning to discover cloudy pool water? That’s so annoying! Yesterday the pool water was perfect and now it has turned a misty white color that looks dreadful. Let’s find out how to clear cloudy pool water easily and quickly.
Swimming pool water can turn cloudy for a number of reasons. Firstly, you may have shocked the pool yesterday and that has made the water milky. This is normal and will clear up in a few days by itself. If you have added too much shock it may take a few extra days to clear up. Otherwise, you may have unbalanced pool chemistry, a calcium build-up in the water, a dirty ineffective filter or you are simply not running the pump long enough each day to keep the pool water sparkling clear. If the cloudiness problem is severe you probably have all of the above issues.
Table of Contents
What is Cloudy Pool Water
Cloudy pool water is a term used to describe pool water that is no longer crystal clear and sparkling clean. The look of the water can range from simply looking a bit flat and losing its sparkle, through being foggy and more difficult to see the bottom to being solidly milky and cloudy.
If your pool water starts to show signs of losing its clarity it’s important to act quickly before the problem worsens and becomes more difficult to remedy.
What Causes Cloudy Pool Water?
The main reasons for cloudy pool water are as follows:
High pH
pH is a scale in chemistry to indicate the level of acidity or alkalinity of an aqueous (water-based) solution. The symbol pH means “power or potential of hydrogen”.
Strong acid is pH 0, strong base (or alkaline) is pH 14 and pure water, at 25C, is neutral at pH 7.0.
A high pH (above 7.6) may contribute to the water becoming cloudy because it can cause a fluctuating balance in the water and render other chemicals less effective in keeping your pool chemistry balanced.
High Chlorine Level
Chlorine, in the form of sodium hypochlorite (NaClO), is used to sanitize swimming pool water. Sodium hypochlorite solution is unstable and rapidly decomposes releasing aqueous free chlorine. The free chlorine kills bacteria, algae and other microbes in your pool water.
The normal Free Chlorine level is 1.0 – 3.0 ppm
If the chlorine level is higher than 3 ppm it may cause the water to turn cloudy.
This may be caused by the salt water chlorinator generating too much chlorine so it needs to be dialed down to fix the problem.
If you have shocked the pool this may cause cloudiness. This is normal and not worry because it will clear up in a few days. Just keep running the pump and filtering the water as normal.
High Cyanuric Acid
Cyanuric Acid (stabilizer) is manufactured for the swimming pool industry as a white, odourless solid compound and is most commonly used as a stabilizer for swimming pool water. The acid binds to free chlorine in pool water slowing down the reaction of chlorine which extends the useful life of chlorine in the water.
On a hot summer day ultra-violet radiation can quickly burn off free chlorine from pool water leaving the water unsanitized and less safe for swimming. Adding the correct amount of cyanuric acid to pool water ensures the free chlorine in your pool lasts longer and dissipates slowly keeping the water sanitized for a longer period.
However, if you have added to much stabilizer to your pool it can cause the pool water to turn cloudy or milky.
Please read our article on How to Lower Cyanuric Acid in a Pool
High Alkalinity
Total alkalinity is a measure of the total concentration of alkaloids (carbonates and other alkaline compounds) dissolved in water. It is a measure of the water’s ability to resist changes in pH by providing capacity to neutralize acid. The right amount of alkalinity helps to buffer your pool water from changes in pH.
Total Alkalinity should be between 80 – 120 ppm.
When the Alkalinity and pH is too high, add hydrochloric acid to the pool.
When the pH level is normal but Total Alkalinity is still too high use sodium bisulphate to lower the Total Alkalinity as this will not adversely change the pH.
High Calcium Hardness
Calcium Hardness is the measure of all calcium compounds dissolved in the pool water. If you sourced your pool water from a bore, dam or river it may be high in mineral compounds such as calcium. The calcium will remain in the pool and cause cloudiness of the water.
This is often overlooked by pool owners because most pool test strips don’t include a test for calcium hardness. You will need a liquid test kit to detect calcium hardness.
The recommended range is 200 to 400 ppm.
There really is only one way to reduce it and that’s to drain some water from your pool and refill with fresh water. If you are only slightly higher than 400ppm you can try draining down to the bottom of the skimmer box. Refill and test the water again.
If the result is much higher than 400ppm you will need to drain more water from the pool.
After each drain and refill, test the water again and rebalance when necessary.
Dirty Filters
Have you cleaned the pool filters – skimmer basket, pump basket and filter cartridge or sand filter? When the filters are unclean it reduces the flow rate of water through the filtration system requiring the pump to be run longer to adequately clean the water. If your pool collects leaves, dust, insects or other debris you may need to clean the filter more frequently.
If the filter cartridge is old maybe it’s time to replace it as they clog up and lose their efficiency over time.
Not Enough Filtration
When your pool was built the pump and filter would have been designed to turn over the entire contents of the pool in 8 to 10 hours. Normally, a pump may be run 3 hours in the morning and 3 hours in the evening but this depends on the season and usage of the pool. However, if your pool is becoming cloudy you need to run the pump longer to clear up the cloudy pool water.
Please read our article on How Long to Run the Pool Pump
How to Fix Cloudy Pool Water
Pool Chemistry
Obviously, if your pool chemistry is out equilibrium you need to fix it before considering the options below.
Please read our article on How to Balance Pool Chemistry
Pool Clarifier
Sometimes the pool water is cloudy as it contains a build-up of very fine particles that your filter cannot remove from the water. The use of a clarifier chemical will help to combine these tiny particles together into larger particles that can be filtered out.
Of course, you will need to backwash or clean your filter after this process.
Pool Flocculent
This chemical works in the same way as clarifier by clumping together fine particles into larger particles. However, the particles will be heavy enough to sink to the bottom where they can be vacuumed away.
You will need to manually vacuum to the waste drain otherwise you would be clogging your filter.
As you vacuum to waste the water level will drop so you need to refill the lost water with a garden hose.
Increase Filtration
Usually you can fix cloudy pool water by increasing filtration.
Start by cleaning the filter.
Run the pump for an extra 6 to 8 hours on the first day. You may want to run the pump for a few extra hours per day until the cloudy pool water has cleared.
Sometimes this alone is enough to clear the pool. Usually you will want to combine extra filtering with a clarifier to accelerate the process.
It’s a good idea to increase the filtration time by an hour every day to ensure the pool water remains clear.
Drain & Refill
Dilute the water to fix cloudy pool water. Do this by draining some water from the pool and replacing it with clean, fresh water. This method is particularly useful when the pool water contains too much cyanuric acid or calcium.
Safety and Handling of Pool Chemicals
Pool chemicals are dangerous and reactive.
Please store all pool chemicals in a cool, dry location and kept out of the reach of children.
Wear gloves and protective clothing when handling chemicals.
Always carefully read the instructions on the packaging.
NEVER MIX CHEMICALS TOGETHER
You should never mix pool chemicals together as they may react leading to fire, explosion or release of toxic chlorine gas. Even mixing dry chlorine with liquid chlorine may cause an explosion.
NEVER ADD WATER TO CHEMICALS, ALWAYS ADD CHEMICALS TO WATER.
You must never add water to chemicals. The chemical may react with the water causing an explosion or the release of toxic chlorine gas that has the potential to damage your lungs.
It is much safer to add a small amount of chemical to a large amount of water to minimize the chemical reaction. For example, if you want to dilute chlorine add a small amount of chlorine to a full bucket of water.
How to Fix a Cloudy Salt Water Pool
The reason salt water pools turn cloudy is the same as for other pools. The same methods to resolve the problem will work in a salt water pool. The only other thing you need to consider is whether the salt water chlorinator is working effectively or not.
Conclusion
Cloudy pool water is a very common issue among pool owners. But it doesn’t have to be your problem. When you follow a basic pool maintenance plan, test your pool water regularly and balance your pool water chemistry following manufacturers’ instructions you should never have to encounter pool water that has turned cloudy.
I hope you found this information useful. If so, please share this web page with other pool owners so everyone can enjoy a problem free pool lifestyle.
