Algae Grows in Pools For A Variety of Reasons

As a swimming pool owner, one of the biggest challenges to deal with is algae. There are a variety of reasons why algae grow in your swimming pool and even if your chlorine levels are within appropriate levels it still might develop. Many times we will hear, my chlorine level is 5 parts per million (ppm), my pH is 7.6, my water is clear but I keep developing algae on the walls of my swimming pool. Even when I brush it regularly and I don’t know why it keeps coming back. This isn’t an uncommon problem and there are a few reasons why this could be happening which we would like to discuss in this blog post.

Filter Run Times

Are you filtering for long enough periods of time? Depending on the time of year the number of hours to filter your swimming pool changes but when the water warms up you should be filtering for at least 8 – 12 hours a day to prevent your water from getting cloudy and from algae growing in your swimming pool. Adequate filter run times are vital to prevent this.

Phosphate Levels

Phosphates are a challenge and can be a nightmare in your swimming pool especially if you don’t what they are, how they affect your swimming pool chemistry, and how to handle them. You can’t physically see them which is the first problem, but as their levels increase in the swimming pool the water could turn cloudy and green! This is where the problem is because even though you have adequate amounts of sanitizer in the swimming pool algae can and will grow. Phosphates, “(also denoted as PO4) are known nutrients to help increase plant growth rates such as in algae.” Simply put, phosphates are food for algae and when their levels increase maintaining a blue and clear pool is extremely challenging. In Las Vegas, we just got through another long summer with many storms and wind and chances are phosphate levels have increased in your swimming pool. Even with adequate levels of chlorine, algae can still form until the phosphate levels or lower.

CYA Levels

There is a direct relationship to the amount of CYA in a pool and the proper chlorine level. The multiplier to figure out how much chlorine (in ppm) you need is .075   In the case of a pool with 40 ppm CYA, we would take 40 times .075 to get minimum chlorine residual of 3 ppm (we always talk about free chlorine here).  A pool with 80 ppm then would require a minimum of 6 ppm free chlorine as 80 X .075 = 6.  Oftentimes in our industry, we hear that 2-4 pp free chlorine is good, with no regard to the relationship it has with CYA.  With this simple example, you can see that a pool with 80 ppm CYA and only a 4 ppm free chlorine residual is asking for trouble (algae)!  You must either lower your CYA level or increase your free chlorine to keep a safe and sanitary pool in this case.

So, if you have algae and you think your water chemistry is good, please remember to check the above because any of these could be the case as well. If you should have any questions, please contact us today!

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