How To Fix Cloudy Pool Water

Pool Care Chapters

How to Balance Free Chlorine vs Combined Chlorine

Cause of Cloudy WaterSolution
AlgaeAdd Chlorine
Ammonia Is Too HighAdd Chlorine
Calcium Is Too HighDrain water to reduce calcium hardness to 200 - 400 ppm
Clogged FilterClean Filter
Not Enough Free ChlorineAdd More Chlorine
pH Too HighReduce pH to 7.2 - 7.4
Too Much Cyanurice AcidPartially drain pool to reduce Cyanuric acid
Too Much Water PressureReduce the pool pump GPM setting until it is set to within the filter’s GPM rating.
Worn out FilterReplace Filter

The most common cause of cloudy pools is combined chlorine. When you first add chlorine to a pool, everything is fine. The free chlorine readily attacks any contaminants. The cloudy pool issue grows as the free chlorine combines with the contaminants and forms what are called chloramines. Those chloramines are what is responsible for the chlorine smell. As they form, there are fewer and fewer free chlorines that are available, and the germs and bacteria that are in the pool are free to proliferate and overtake your pool. Algae grow and the smell of ammonia becomes difficult to ignore.

The smell is your first indication that chlorine balance is out of whack. If you smell the ammonia or notice growing cloudiness, you should immediately bring out a chemical testing kit. With those kits, you can measure the free chlorine and the combined chlorine.

If your combined chlorine is higher than .5 parts per million (ppm) and you have free chlorine that is less than 3 ppm, it is time to “shock” your swimming pool. This means that it is time to add a sufficient amount of chlorine to kill any bacteria or algae that are trying to set up shop in your pool. If you need some help with that, we actually have a guide on how to shock your swimming pool.

All of this applies whether you have a saltwater pool or a standard non-salt water pool. Saltwater chlorine generators (SWCG) will not be sufficient for this particular issue, so you will need to shut it down for the moment. This task will require your personal attention.

Is it Ammonia or Algae?

The quick but unhelpful answer is that it could be. First, you can test if it is algae by adding a fair amount of chlorine into your pool. You will want to wait until after sunset because adding pure chlorine is highly unstable. If left in direct sunlight, it will largely evaporate within an hour.

All of the free unstabilized chlorine is highly reactive and it will quickly bind with any algae particles that are in the water. In the morning, before the sun has a direct line of sight to your pool, you should test the water to see how much free chlorine is still in the water.

If there is algae in the pool, the free chlorine will quickly bind with it and form combined chlorine. If the free chlorine drops by 1 PPM, you will know that you have an algae issue. If you need some help taking care of that, we have some algae removal guides that can help. However, before you can remove the algae, you will need to know its type.

If the chlorine doesn’t drop so drastically, it is probably an ammonia issue. Ammonia has a tendency to build up right as pools are about to open. Because pools are not used frequently during the winter months, balancing chemicals tends to be put to the side. The low-free chlorine and cyanuric acid that would have otherwise kept your pool clean, are usually too low to keep the ammonia at bay. This quickly leads to cloudy waters. No worries, however, the issue can usually be quickly resolved. 

Filter Issues

Clogged or Old Filter

A clogged filter is a useless filter. The reduced water flow and the diminished ability to actually filter the water will quickly create issues. If a filter is left alone for too long, the buildup will eventually cause the filter to do very little filtration. If you stay on top of it, clean your filter, and backwash when appropriate, your pool will give you a lot less trouble.

Even if you do keep your filter clean, you will eventually need to swap it out entirely. Depending on the type, it can be a relatively painless affair. Thankfully, no matter the type, it will also be an uncommon one. 

All filters must be cleaned and replaced periodically, how often they need to be cleaned or swapped out can vary greatly depending on the type of filter you are using. If you want to know more about that, you can click over to yet another one of our guides about the Best Types of Pool Filters for a comprehensive breakdown of the benefits and disadvantages of each type of pool filter. It will go into the frequency of how often to clean and change each filter type.

Too Much Water Pressure
If there is too much pressure on the filter, it can push the contaminants straight through it. This is especially true for cartridge filters. Cartridge filters are fantastic, but they need to be used on small and medium pools. The larger pools require a higher Gallons Per Minute to maintain a sufficient turnover rate to keep the pool clean. The unfortunate reality for cartridge filters is that they can only handle lower-pressure systems. 

Look up your filter. Check to see what GPM it can handle, see what pool pump setting you have set (If there are multiple settings), and adjust accordingly. 

Maintaining Chemical Balance

In addition to Chlorine, there are several other chemicals that must be balanced. Describing this crazy concoction of chemicals as a balancing act is a great way to describe it. As you add one chemical, it starts to throw off another. Getting everything just right can be a bit of a headache if you don’t know what you are doing. If you are just starting out, you don’t need to get anxious. Knowing how to balance your pool chemicals will become easier with time and repetition. Here’s a brief rundown on why balancing each of these pool chemicals is necessary to maintain a crystal clear pool. We’ve already talked a bit about Chlorine and Cyanuric Acid, but we’re going to quickly repeat ourselves for the benefit of those that skipped ahead in this guide.

You Might Need More Chlorine

Chlorine is your main fighting force against the corrupt powers of algae, bacteria, and other contaminants. While it is super effective, it is also highly unstable and prone to quick evaporation. On a hot sunny day, almost all of whatever chlorine you add will evaporate within a matter of minutes. That is why Chlorine requires a stabilizer.

Is There Too Much Cyanuric Acid?

Cyanuric acid is that stabilizer. Stabilizers are sometimes called pool softeners, and they make weak bonds that are strong enough to keep the chlorine in the pool. The bonds are weak, so they can often be overcome by stronger potential bonds of whatever contaminants are in the pool. When the chlorine disconnects from the cyanuric acid to bind with the contaminants, it creates chloramines. Additionally, when it binds with the algae proteins, the reactive nature of chlorine mutates the molecular shape of the protein. This reshaping is what destroys the algae and bacteria.

If you have too much CYA stabilizer in your pool, your chlorine will be too stabilized in its bond with the CYA that it will never bind the impurities that are hanging out in your pool. This leads to the type of cloudiness that you are likely addressing right now.

Is the Calcium Too High?

Calcium can be a troublesome chemical. It isn’t too difficult to balance, but it can be more difficult to reduce than the other chemicals. It doesn’t evaporate like chlorine, so the only way to get rid of it is by draining the pool. If the levels aren’t too off, you might be able to get away with adding some water. However, that isn’t a great solution since your water levels should always remain at the midpoint of the skimmer’s inlet.

When calcium is too high, the excess calcium can be the cloudiness that is obscuring what would otherwise be crystal clear pool water. Too much calcium also has the unfortunate effect of covering the surfaces of your pool walls, floor, and pool equipment such as the filter. When the filter is covered in calcium, this can cause a secondary source of contaminants that add to the cloudiness. If you use a testing kit and make sure to keep your calcium hardness levels between 200 and 400 parts per million, you should be fine as far as calcium goes.

The pH Balance Might be Too High or Too Low

The calcium and chlorine in your pool are highly dependent upon your pool’s pH balance. While a high or low pH balance causes a pool to immediately become cloudy, an improper pH balance will prevent calcium and chlorine from performing their functions.

If the pH is too high, calcium will be unable to dissolve. Calcium would have been an invisible ally, but that high pH made it become murky water. Lowering the pH should return the pool to a clear and pleasant state.

When the pH is too low, it means that there is too much hydrogen floating around the pool. Chlorine is only effective if it can bind with the contaminants in your pool. When there is too much hydrogen in the pool, the chlorine will be too busy bonding with the hydrogen to do its job of cleansing your pool. The result is that your pool becomes dirtier and cloudier because the chlorine isn’t doing its job.

Buy Testing Kits to Find Out if Your Pool Chemicals Are Balanced

This is non-negotiable if your goal is to maintain a healthy pool. Chemical balancing requires constant supervision and continuous adjustments. The balance is fragile and can literally shift from healthy to unhealthy in minutes.

As far as the cloudiness goes, you will need the right amount of cyanuric acid (chlorine stabilizer) to protect the chlorine from the evaporating effects of the sun. The pH needs to be high enough to activate the chlorine and clear the cloudy pool, but low enough so it won’t irritate your eyes or skin. The calcium hardness levels need to be high enough to prevent corrosion of the pool equipment and filters, but not high enough that it causes scaling and covers the pool filters.

We don’t have a particular loyalty to any brand, but here’s a link to one of the higher-rated kits. At the moment, this poolmaster kit costs $18.78. It’s a good price for now, but it looks like it might be more expensive at a later date. If it goes up higher, you should probably find another brand. Testing kits are cheap and you’ll go through them fast if you are performing pool maintenance as often as you probably should.

Use PoolMath to Make Pool Maintenance Simple

We recommend using an app called PoolMath to make all of this a lot easier. You add your pool details into the app. It gets pretty detailed because it honestly needs to be detailed. Do you have a plaster pool? What type of sanitizer are you using? What’s the volume of the pool. What’s the flow rate of your pool pump? What’s the current water pressure?  This app will track all the details, including the local weather, because precision is key to knowing what and how much you need to add. 

It takes the guesswork out and makes pool maintenance more regimented. If you choose the option, it will give you reminders to perform different tasks. Ultimately, if you want a crystal clear pool, you should download this app right now. We aren’t paid or connected to the PoolMath app. We just highly recommend it because it has made a difference for many of us.

The Pool Care Handbook & Video Course

by Swim University
This is an illustrated e-book with detailed videos and step-by-step instructions on how to best care for your swimming pool. 
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