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Swimming Pool and Spa Filter Types: Sand Filters


What Is A Sand Filter For Swimming Pools and Spas?

All of our pools need a filter. Period. All bodies of water that people will be swimming in need to have a means or removing contaminates from said water. Filtration aids pools in spas in the following ways:

  • Water Clarity
  • Water Cleanliness

These two areas are arguably the most crucial elements in operating a pool. If the water in the pool or hot tub is not clear, it is a major safety hazard not to mention it is quite unsightly. Cloudy or unclear water is a hazard because someone who has sunk to the bottom of the pool or hot rob will not be visible if the water is cloudy. Cloudy water also indicates filth and contaminates that can infect and affect your swimmers adversely.

Filtration, alongside with disinfection, is key in preventing dirty and cloudy water.We capture this filth and debris inside of our filters through the use of a filtration media. There are numerous media on the market used for the purpose of filtering our pool and hot tub water, and sand media is one of the more popular ones. In this article we will be exploring one of the most common types of filtration media: Sand.

How Does Sand Work In A Pool Filter?

Sand Filters are generally filled with high grade silica sand. This sand is extremely porous. When we fill our sand Filters with this silica sand, the water passes through said sand and unwanted matter within our water gets stuck inside those pores. Once inside those pores, the contaminate becomes trapped within the sand bed, thus filtering our swimming water. It is a very simple yet effective means to clean our water. 


What Are Some Benefits of Sand Filters For Swimming Pools?

Sand Filters have quite a few great benefits:

  • They are easy to operate
  • They have a decent microbic filtration power (25 microns)
  • They are fairly easy to maintain
  • The sand itself is fairly easy to replace

Sand filters tend to do all the work without your help. So long as the conditions are right, the sand filter will only need your help backwashing (or intermittently cleaning), and changing the sand every few years. 


Sand Filters are also capable of trapping debris down to 25 microns. To put it into perspective 1 micron measures in at 1/25,000 of an inch. It is also good to know that debris is no longer visible to the naked eye after 40 microns, so 25 microns is microscopic. Needless to say our sand Filters offer great filtration! 

Maintaining sand Filters can also be very low maintenance. So long as you are backwashing your sand filter regularly you should experience very few drawbacks in operation. 


When Should I Backwash my sand filter?

High Rate Sand:When the pressure rise 8-10 over starting pressure on your pressure gauge, then and only then, will you want to backwash. And even then, you only want to backwash until the water running through your waste sight glass goes clear. 

Rapid Rate Sand: When the influent and effluent gauges read 10-20 psi difference, then, and only then will you want to backwash. And again, you only need to backwash until the sigh glass on your waste line goes clear. 


Do I Need To Backwash My Sand Filter Every Day?

There is no “regular” schedule in which you should backwash. Simply watch your gauges and use the aforementioned backwash recommendations and you will be good to go!


Do I Need To Change My Pool Filter Sand?

Sand Filters are also quite easy to change on your own. In fact, the owner’s manual to your filter contains all the info you need to effectively change your filter sand. Please do note that silica sand is dangerous when inhaled so be sure to wear a dust mask whenever you are interacting with it personally. 


When Do I Need To Change My Pool Filter Sand?

There is no set time when you should change your filter sand. Generally high rate sand is good for 3-7 years depending on condition. In fact, there are some filters that allow you to never change your filter sand, as long as you are maintaining that sand bed properly! The general rule of thumb is to check the sand itself. The sand will begin to clump together from grease deposits and it will also begins to darken and become impacted with debris. Once you notice these conditions, it is likely time to change your sand. 


What Are The Drawbacks To A Sand Filter? 

Again, sand Filters are quite good at what they do as we’ve just read. But there are a few things to watch out for with sand Filters:


  • Channeling
  • Broken laterals
  • Wasted Water

Channeling is the process of your water bypassing the sand altogether and returning to your pool unfiltered. Channeling occurs when the sand filter is not properly maintained through the activity of backwashing and through the monthly addition of a filter degreaser. 

Broken Laterals can lead to sand blowing into your pool or spa. These laterals are located on the bottom of your sand filters and are the last barrier between your sand in your filter and your pool. Once one of these breaks, sand can easily escape into the pool or hot tub. To prevent broken laterals, make sure to keep your water chemistry as well-balanced as possible. Sadly though, laterals are a component in your filtration system that does have a lifespan. For good measure, Pool Training Academy suggests that you change all of your laterals every time you change your filter sand. It is also highly recommended that you replace ALL the laterals when you find sand in your pool simply because it is hard, sometimes nearly impossible, to find which lateral could be the culprit. 

Wasted Water comes from the fact that your sand filters use a TON of water to clean! Because of this, it might not be a great idea to install a sand filter in an area where water is extremely scarce. There are other filtration options out there that use much less water than sand filters, and as such, may be better for operators in these areas. 


Can I Make My Pool Sand Filter Better?

You are more than welcome to make your sand filter filter down to an even stronger microbic level by using a product called SEA KLEAR PRS. When used correctly, this product can turn your sand filter into a filter that goes down to a 0.5 microbic power!


Do I Still Need To Use Chlorine If I Have A Sand Filter?

Simply put, yes, you still absolutely need chlorine. Filtration is only one safeguard against pathogens and contaminates within your water. It is crucial to maintain your chlorine between 2.5-4.5 ppm in order to kill or inactivate any pathogens that guests might interact with inside the water itself. 


How Do I Learn More?

Knowing the ins and outs of sand filtration is only one of the many challenges pool and spa operators face on a day to day basis. This article has given you a good, but brief understanding of sand filters. Making sure you have the ability to learn more and, more importantly, as questions is crucial for you as an operator. Thankfully Pool Training Academy offers Certified Pool Operator® Classes year-round and close to you. We offer CPO® classes in Denver, San Antonio, Texas, Los Angeles, CA, Nashville, TN., and much much more! Please click here to sign up for the class that will ensure you are the best pool and spa operator you can be. 


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