What are the Causes of a Green Pool?

What are the Causes of a Green Pool? | Dolphin Pool Supply Dallas Texas Dolphin Pool Supply and Service has always believed that most swimming pool issues boil down to either water chemistry or filtration and the circulation. A green pool is no different. In this article, our pool service experts will go through the two main reasons why you might find yourself with a green backyard pool and steps you can take to treat it right away.

Reason 1: Chemistry Issues

More often than not, a swimming pool starts turning green due to a lack of chlorine. The free chlorine level should be maintained between 2.0 and 3.0 parts per million. We recommend the use of chlorine tablets in a floater or a feeder to maintain this level of chlorine in the pool. Pool water should be tested at least once or twice a week to ensure that the level of chlorine is maintained at the recommended level.

In addition, the pool water should be shocked routinely with granular chlorine (calcium hypochlorite) in most cases. We recommend at least once every two weeks, or more often in the heat of the summer. The general rule is to shock with at least one pound of calcium hypochlorite per 10,000 gallons of pool water. A shock treatment will raise the chlorine level very high for a short period of time, killing bacteria and organic waste, and making all the chlorine in the pool free and available to sanitize the pool water.

pH will also have an effect. If the pH is high, your chlorine is slow to react, and algae can begin to form, making the pool appear green or cloudy. If the pH is low, the chlorine will be “hyperactive”, reacting quickly, and dissipating out of the pool too rapidly, causing a low chlorine residual.

If the Stabilizer (Cyanuric Acid) level is too high, the chlorine also reacts very slowly, is less effective at killing bacteria and algae, and will actually stay in the pool too long, leading to high chlorine levels that cannot clear the green color out of the pool. This situation normally indicates a need to get your pool water analyzed by a swimming pool professional. Take a quart sample of the pool water into one of our locations for a computerized water analysis and help with clearing the green color out of your pool.

Reason 2: Filtration Issues

If the swimming pool filtration system is performing poorly or not running enough hours, the debris that the filter would normally filter out can remain in the pool water. This causes the sunlight to refract through the pool water gives it a greenish tint. Let’s look at the various filter types and what you may need to look for when the pool looks green.

Sand filters do not filter very small particles and therefore are notorious for having difficulty when trying to turn a green pool back to blue. It doesn’t mean that it won’t get done, it just takes longer for sand filters to filter out the fine debris. The sand can “channel,” the backwash valve gasket or the O-ring can go bad, allowing the debris to bypass the filter and shoot back into the pool. The laterals beneath the sand can crack and allow the sand from the filter into the pool, making it even harder to turn the pool around.

Diatomaceous Earth filters take in very small particles and can turn around a green or cloudy pool quickly. You should always check your pool return jets when adding DE to the skimmer to see if the DE is going through the filter and shooting into the pool. This indicates a filter issue that needs repair. If the filter pressure is building up very quickly it indicates a need to take apart and manually clean the girds, or that you may not be using the proper amount of DE. The girds within the filter can “cake up” with DE and this is another reason the filter needs to be taken apart and cleaned.

Cartridge filters take in pretty small particles as well and normally clear a green cloudy pool fairly quickly. These cartridges normally last a year or two and then can no longer do the filtering job. As they filter out debris, the pressure on the gauge will rise and the flow through the filter is reduced. When the pressure does rise, the filter is not filtering the debris and that will indicate that the cartridges must be cleaned.

If you need assistance with your pool, give us a call! Or, bring in a sample of water if you have a green pool, we can help you get it back to a sparkling blue in no time!


About Dolphin Pool Supply and Service

Dolphin Pool Supply is an employee-owned company which has been in the business of swimming pool supply and services since 1957.  Dolphin Pool Supply values customers as the most important asset of the business taking their every need with high regard to ensure client satisfaction.

Dolphin Pool Supply provides swimming pool supplies and services in Dallas and Flower Mound.

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