Causes and solutions for cloudy pool water

In this article we are going to deal with one of the most common problems with a conventional swimming pool (as opposed to a natural swimming pool). So, if you have found your pool water to be cloudy, the issue you are facing probably is, as you already must have suspected, an imbalance in the water. A well maintained swimming pool needs a proper balance between the following 4 factors: Chemicals, circulation, filtration and cleaning.

photo from

We will go through and take a look at various factors and how to deal with them. The most frequent issue we see when it comes to cloudy pool water is a problem with algae overgrowth. Perhaps you haven’t been able to maintain the pool as you should for some time, perhaps you had a party and the pool filled up with people waring sunscreen, lotion, perfume etc etc… Well, whatever happened, we need to deal with it.

Physical damage or organic matter causing cloudy pool water

First of all you should do a visual inspection of the pool. Does the water have a green or greenish color. If it does we are dealing with severe algae growth and we would need to determine why we have that. There is no use in treating the symptom without dealing with the cause. Therefore, go ahead and check to see if you see something unusual like a leakage or a filtration, does the pool sides or base look whole or are there any cracks or chips are there leaves or other organic matter in the pool water?

If so then this may have caused the imbalance in your pool water. So if you see anything that can indicate a leakage or a filter malfunction attend to that first. If you have organic matter like leaves and stuff in your pool, you would want to scoop that up first.

Filter leakage causing cloudy pool water

If you have a D.E. filter (Diatomaceous Earth) or a cartridge filter open it and clean it and replace any broken grids or cartridges. If you have a DE filter mind the order of the filters.

If dirty or broken filters is the problem then it may take a couple of days for your pool water to clear. We assume that you have done your regular maintenance regularly. That means backwashing your D.E. filter until the backwashed water comes out clear. Even if the water comes out clear you should not backwash less than 3 minutes.

Chemical imbalance causing cloudy pool water

A modern swimming pool uses several different agents to achieve different things:

  • Disinfectants like chlorine is used to destroy living organisms in your water. As a pool will loose chlorine through evaporation, absorption etc.
  • Chlorine stabilizer like cyanuric acid is used to slow that effect down
  • Algaecide is used to prevent and to kill algae

In addition soda ash and also baking soda is used to raise the PH when needed and muriatic acid to lower the PH if that is necessary. The PH of your pool should be somewhere between 7.4 and 7.6.

Every pool owner should have a proper test kit to monitor the chemical balance of the pool. The Taylor K-2006 is a pretty good option to go for, but for quick measurements you could use a strip tester like AquaCheck .

The number one reason for cloudy pool water is actually plain and simple lack of chlorine. Perhaps the weather had been particularly hot or it has rained heavily, perhaps you forgot or perhaps you had a pool party and many people jumped into the water. All these are factors that may zero out your chlorine levels.

To keep your pool sparkling clean and healthy you should keep it within these values:

  • Chlorine: 1.5-3.0 ppm
  • Conditioner: 40-100 ppm (mg/l)
  • pH: 7.6-8.0 ppm (mg/l)
  • Alkalinity: 90-130 ppm

Taylor Technologies Inc has some good Youtube videos showing how to use their products.

Test strips from Hach

The most interesting value here is the total chlorine. However, the combined chlorine is the “used” free chlorine so to speak, as the free chlorine disinfects its byproduct is combined chlorine. Combined chlorine is what smells of chlorine and it will also sting in the eyes, and when you have too much of combined chlorine, it may make your pool cloudy.

In both cases, both lack of chlorine and too much combined chlorine, the solution is often to “shock the pool”. Shocking the pool is done by bringing the chlorine level up to 10 ppm. As the sun “eats” the chlorine, the shocking of the pool is best done at sunset or at night. In addition to the chlorine shock it is a good idea to run the pool for 8 hours or two cycles. “To run the pool” is nothing else that to let the pumps run to clean pool.

This brings us over to another reason that may have had your water go cloudy.

Lack of maintenance causing cloudy pool water

You may no be running your pool long enough. A general rule of thumb is that you need to run all the water in your pool at least once through your pool filter. During summer it is recommendable to run it twice. To run the water through the filter once is called called a cycle. How long this takes depends on how big your pool is (how many gallons of water it holds) and how big the pump is.

This is really something you should know about  your pool, and if you do not then you need to find out to avoid this happening again.

Use this pool volume calculator from HTH pools to calculate how much water your pool holds, then check your pool pump. It will probably say how much water it can run in 1 hour. Then do the math.

If you have adjusted the PH level recently? If you have added soda ash or baking soda your pool water may go cloudy for a while, but it should clear up in about a day or so. Also if you have had high alkaline values or high calcium values (water hardness) that may cause cloudy water.

So now that you know a bit more about what may be causing cloudy pool water and how to control it.