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Swimming Pool Filter Videos - Maintenance, Troubleshooting & Operating Tips

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Pool Filters

Is A Cartridge Filter Better Than A Sand Filter?

Swimming pool cartridge filters are a superior product than a traditional silica sand filter in the sense that they can physically remove smaller particulate from the water than sand filters can. This can lead to a reduction in turbidity in the water which may not be too noticeable during daylight but is very visible at night if you have the light in the pool on. Also, since pool water clarity is at least 50% reliant on proper filtration, a more robust filter could result in cleaner and clearer water in your pool.

Another advantage of cartridge filters is that they do not require weekly backwashing maintenance like sand filters do. Many urban areas are now placing restrictions on where you can discharge pool water, especially salt water pools, so a cartridge filter would be a big advantage in these areas. The downsides of cartridge filters are the initial price as well as the replacement cartridges which must be replaced every 3-5 years. These replacement cartridges are often nearly as expensive as the filter was initially so research replacement filter cartridge prices before you choose which filter you are going to buy. From an economy viewpoint traditional sand filters are more than capable of keeping almost any pool clean and clear and if you are on a budget then a cartridge filter, while better, may not be necessary for your pool.


How Often Am I Supposed To Backwash My Sand Filter?

The pressure gauge on your pool filter is your reference point that indicates when you should backwash your filter. In order to set up a maintenance schedule like this you will need to determine what your "clean operational pressure" for your system is. Since the amount of resistance to flow in your system will be 100% unique to your installation, every pool needs to determine its own unique COP. Even write on the wall with a pencil next to your filter what your pressure is so this information can not be lost or forgotten.

A new pool system is easy to determine your clean operational pressure as this simply is the initial start up pressure of the system once it is primed and running smoothly. On existing pool systems you just need to backwash your filter extensively, usually three times longer than you normally would just to be sure, and then note the pressure on the filter gauge after you start up the system to filter again. This represents your ideal operating pressures with your system. This number can be anywhere from 5PSI to 25 PSI. You need to backwash your sand filter any time the system pressure rises 5-7PSI above your clean operational pressure value.





Broken lateral in sand filter - Why Is There Sand In The Bottom Of My Pool

The most common failure for a sand filter is to have a broken or cracked component inside the filter that allows the sand to escape the filter and travel through the return lines back to the pool. Sand in the bottom of the pool is a big sign that there may be a filter problem however if the sand is typically found extending out in a line in front of where your return ports are, then you almost certainly have a failure inside the filter.

The common components that can fail inside of the filer is the standpipe, which is a larger pipe that runs vertically up the center of the filter, and the laterals which are small "fingers" that extend out from the bottom of the standpipe. These smaller laterals can easily crack both during installation as well as later in the life of the filter without apparent cause. To fix you will need to open the filter, remove the sand, locate the cracked part and replace it (or replace the entire standpipe and lateral assembly, and then refill with new sand. The cost of having this service completed for you is fairly expensive compared to the the cost of a new filter. If your filter is 7 years old or less then a filter change would be fine however if the filter tank and head valve are already older than 7 years then you should consider replacing the entire unit.


How Long Should I Backwash My Sand Filter?

This video shows the proper methods for changing between filter settings, as well as which settings you should use and for how long when backwashing your sand filter. Most importantly is that the pump needs to be turned of prior to changing the filter handle orientation. If you attempt to move the filter handle with the system running run can possibly displace the spoke gasket which will require service to repair. You should run the pump on "backwash" setting followed by the "rinse" setting if your filter head has this option.

The length of time that you backwash for will depend on how dirty the filter is to start with. For this reason using arbitrary time like 1 minute or 3 minutes is not ideal. Ideally you want to know what the clean operational pressure of your pool system is and then you would simply backwash in 1 minute increments until you achieve your clean operational pressure. Another less technical method is to use the discharge sight glass and watch until the water is running clean through the sightglass, add thirty more seconds, and then rinse before returning to the filter setting.


How Often Should I Replace My Filter Sand?

There is a rift in the pool industry among technicians as to how often you should change the sand in silica sand filters. Many pool companies take a general approach and say to replace sand every 7 years or so. It is important to identify the potential longevity for the sand in the filter however this does not mean that you should open a perfectly functional filter at the 7 year point and change the sand. If the pool is clear, the system pressure is lower than 25PSI, and the filter is not leaking then you should not change the sand until there is a problem.

Some pool technicians believe that the extra sediment and wear on the sand in silica filters can aid in water clarity by reducing the micron size of particulate the filter can remove. The concern with older sand is it is possible that channeling of the sand happens over time where very old sand can solidify and channels, or paths, in the sand develop that the water travels though. If this happens then the water is no longer being filtered properly, pr some times at all, and would be evidenced by turbidity in the water of the pool. If your water is clean and clear then you do not likely have channeling of the sand in your filter.


How To Choose The Right Size Pool Filter

Most pool builders can not calculate the size of pool filter that you need of your pool but instead rely on industry knowledge that certain filters will work on almost any pool. The reality is that there is a specific calculation that you can perform to determine which filter is the right size and this has to do with turnover rates of the pool and flow rates provided by the pump.

A 16x32' pool has close to 20,000 gallons. In order to filter this pool properly you will need to filter 60,000 gallons of water every 24 hours. This means 2500 gallons per hour and just under 42 gallons per minute. The correct size filter for this pool would have a maximum GPM rating OVER 42 gallons per minute. Unfortunately many pool builders way oversize the filter, like in this example using a filter with a max GPM of 90 GPM would be way overkill. This flip side of this equation is that if the filter is too large then it will not backwash properly and for this reason simply choosing a filter that is "for sure" large enough is not a good idea. Calculate the max GPM you need and buy the next largest size filter to err on the side of caution. There are many different sizes of filter so there is no need to oversize by 3 or 4 models larger.


How Often Should I Replace The Cartridges In My Filter?

Since replacement cartridges are almost as expensive as a new pool cartridge filter you certainly want to get the maximum lifetime out of your filters. It is fairly easy to tell when it is time to replace them as they are just made from paper and will begin to deteriorate over time. Eventually they will develop holes in the cartridge paper which will require to be replaced for the filter to function correctly. Having a pump that is too powerful for your system can cause the paper to wear prematurely however cleaning process for the filters is the most common way to damage them.

Proper chemical balancing is important for every component of your pool, your cartridge filter included, but other than this the biggest factor that will impact the longevity of your filters is your cleaning procedures and schedule. Pressure washing is a common cleaning process however this can easily reduce the longevity of your filters since they are made from paper and the pressure washing can potentially damage them. The best cleaning process is to soak for 24 hours in a degreasing agent and then rinse thoroughly with a garden hose.


How To Clean My Cartridge Filters?

There are two main ways to clean a cartridge filter properly depending on what the problem is with the filter. The two main problems that you can encounter are oil soaked filters and filters that have developed calcium scale. Sun tan lotion, body oils, makeup, sweat etc are all forms of oil that a cartridge pool filter will absorb. Using a garden hose to simply spray down the filter will only remove the surface debris but will do nothing to remove the oils that are saturating the paper of the filter. Filter cleaning products that you buy in pool and spa stores are essentially a degreaser made for cutting grease and not creating bubbles - exactly like automatic dishwasher detergent.

Once a pool season or twice yearly you should soak your cartridges in a degreaser. Automatic dishwasher granular detergent can be used at the ratio of 1 cup of detergent for every 5 gallons of hot water. Soak the filter overnight in a large tub and rinse in the morning. The other problem that filters can develop is much less common and is a result of hard source water or improper chemical balance, and that is scale on the filters. This will prevent water from passing through the filter and the degreaser treatment will not remove it. You will need to soak the filter in descaler, or 7 parts water to 1 part muriatic acid, which will dissolve the scale.

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