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Filters

The pump & filter system is the heart of your pool and it does most of the cleaning and clarifying.

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Getting started with pool filters

pool filters

Pool filters are crucial because they take out dirt, debris, and other impurities to maintain the water in a swimming pool clear and clean. This promotes the general wellbeing and aesthetic appeal of the pool as well as the wellbeing and safety of swimmers.
Without a working filter, a pool’s water can become hazy and unhygienic, which can encourage the development of dangerous germs and other microbes. A pool filter can also assist to extend the life of the pool’s plumbing and equipment by avoiding clogs and other problems brought on by the accumulation of dirt and debris.

There are three different styles of filters commonly used for swimming pool filtration. The regulations for what filters can be used for a residential or commercial swimming pool change from city to city and state to state, however you will find all three types just about everywhere you service swimming pools at DPS.The three types of filters we will discuss here are D.E. or Diatomaceous Earth Filters, Cartridge Filters and Sand Filters. We will also discuss the principles of how they work and their maintenance.

pool filters

Diatomaceous earth filters

Diatomaceous earth pool filter

Diatomaceous Earth (D.E.) Filters can be metal, fiberglass or plastic just as all other filters. Water is pushed through a D.E. filter, just as any other filter. The pump pushes the water into the filter past a series of 8 D.E. filter grids. These grids have a plastic skeleton and are coated in a fine screen-like mesh material. This material is made to hold a filter media called Diatomaceous Earth (D.E.) which is also commonly called filter powder. It is a very fine powder, much like baby powder. The filter grid’s job is to hold the powder, while water is pushed through and inside the filter grids and then returned to the pool. Any dirt and debris is held by the D.E. powder while the clean and filtered water is returned to the swimming pool.

What is diatomaceous earth?

Diatomaceous earth, also known as DE, TSS, diatomite, diahydro, kieselguhr, kieselgur or celite) is a naturally occurring, soft, chalk-like sedimentary rock that is easily crumbled into a fine white to off-white powder. This powder has an abrasive feel, similar to pumice powder, and is very light, due to its high porosity. The typical chemical composition of diatomaceous earth is 86% silica, 5% sodium, 3% magnesium and 2% iron.
Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae. It is used as a filtration aid, as a mild abrasive, as a mechanical insecticide, as an absorbent for liquids, as cat litter, as an activator in blood clotting studies, and as a component of dynamite. As it is also heat-resistant, it can be used as a thermal insulator.

Filtration

The most common use (68%) of diatomaceous earth is as a filter medium, especially for swimming pools. It has a high porosity, because it is composed of microscopically-small, coffin-like, hollow particles. It is used in chemistry under the name Celite as a filtration aid, to filter very fine particles that would otherwise pass through or clog filter paper.

It is also used to filter water, particularly in the drinking water treatment process and in fish tanks, and other liquids, such as beer and wine. It can also filter syrups and sugar. Other industries such as paper, paints, ceramics, soap and detergents use it as a fulling material.

    • When a D.E. filter grid’s mesh material is damaged it allows the D.E. powder and any other dirt and debris to travel through the tear in the mesh and return back into the pool and in this event you will notice “white cloud” shooting out of the pool return(s) that will later on settle on the bottom of the pool.
    • Diatomaceous Earth is added to the filter through the skimmer while the pump is operating. It mixes with the water inside the skimmer and within the plumbing from the skimmer to the filter where, once inside the filter it coats the filter grids.
    • Add 1 lbs. of D.E. per each 10 square feet of filtration area of the filter. For example a 60 sq. ft. D.E. filter(most common) would require 6 lbs. of D.E. in order to function and filter properly if it’s full charge. If only re-charge after backwashing, 60% of the full charge will be sufficient, in that case about 4lbs.

As the filter collects dirt and debris the pressure within the filter gets higher. Every week or two, depending on how much debris the filter is holding and its filter pressure, the filter should be backwashed. When a filter is backwashed it changes the direction of water flow and instead of the water flowing through the grids and back into the pool it is redirected to flow from within the grids blowing outward and returns to the backwash line. Flowing out the filter grids instead flowing into them blows the dirt and debris filled D.E. powder off of the grids. Backwashing the filter will get some of the old D.E.(about 40%) and dirt out of the filter but not all of it and that’s why we need to recharge about 60% of D.E. back thru the skimmer after backwash.

Every season, a D.E. filter should be taken apart and cleaned manually by removing and hosing off all the grids individually, making sure each is thoroughly inspected for tears or damage and cleaned, rinsing it off with a garden hose. This is generally called a “filter sanitation”. Once the filter has been inspected and sanitized, reassemble it. Make sure the filter tank rubber o-ring has been lubricated with a Teflon based lubricant. “Magic Lube” is an excellent brand of Teflon based lubricant used for rubber o-rings. Once the filter is back in its normal operating mode, replace the D.E. powder with fresh D.E. adding it through the skimmer. To backwash a D.E. filter there will be either a push/pull style of handle, a multi-port type of handle or a metal bar at the bottom of the filter that needs to be moved into the opposite direction.

Further notes regarding diatomaceous earth filters:

  • To backwash a D.E. filter first make sure the pump is off. Next find out where the backwash line goes to.Next move the backwash valve into the backwash position. This valve could be a push/pull valve, a multi-port valve or a metal bar protruding out horizontally from the bottom or the filter. Turn the pump back on and the filter will be in its backwash cycle. Allow it to backwash for about 60 seconds.
  • Once the filter is backwashed or sanitized put the backwash valve back into the pool circulation or filter setting. Turn the pump back on. When adding Diatomaceous Earth through the skimmer to recoat the filter grids, be careful to not breathe in the powder as it can be hazardous to your health. Add 1 lbs. of D.E. powder per each 10 sq. ft. of the filtration area.
  • Once you add the D.E. powder through the skimmer, carefully, one scoop at a time, check the return lines in the pool and spa. If you see any D.E. returning to the pool then you have a problem inside the filter. This problem could be a tear in one of the filter grids or a missing o-ring. This problem could also occur if the filter was reassembled incorrectly. If you do not see any D.E. powder returning through the return lines than your filter is working properly.
  • When doing a filter sanitation it is good to replace the filter tank o-ring about once per year. When you replace the filter tank o-ring be sure to have the correct replacement o-ring or else it may not fit properly or seal the tank. You do not want to have any leaks on the tank as that would cause the swimming pool to lose water and the filter to drain down and empty when the pump turns off.
  • When sanitizing a filter be sure to clean up any mess and do not hose off the filter grids in a place that would make a mess of the customer’s yard. This would be seen as unprofessional and careless.

Cartridge filters

Cartridge pool filter

Cartridge filters are very similar in function, shape and size to D.E. filters. Often a manufacturer will use the same body of a D.E. filter and only change the insides to hold a cartridge or several cartridges rather than D.E. filter grids. Cartridge filters operate in a similar manner as D.E. filters in that the pump pushes water through them, however the difference is in that rather than having grids to hold D.E. powder, within the filter is a large cartridge or a series of smaller cartridges that hold dirt and debris. Most commonly 4 cartridges are inside filters in our area.

These cartridges require no additional media to filter, as a D.E. filter does(D.E. powder), and cleaning them is quite simple. Cartridge filters do not backwash as a D.E. filter does and they don’t have a multiport valve. To clean a cartridge filter when it gets filled with dirt and debris and the filter pressure rises you merely have to remove the cartridges from inside the filter and hose them off with a garden hose or cartridge cleaning tool that was explained in the first section of this handbook. This cleans the dirt and debris from the cartridge making it clean and ready for use again.

A cartridge filter will have a rubber tank o-ring, just as a D.E. filter does and such should be lubricated just as with a D.E. filter. The disassembly and reassembly of a cartridge filter will be similar to that of a D.E. filter with the exception of having a large or several smaller cartridges inside instead of filter grids.

Cartridge filters do not filter as thoroughly as D.E filters do, being that Diatomaceous Earth is a much finer filter media; however they are commonly found and work well. After cleaning and reassembling a cartridge filter, turn the pump on and make sure there are no leaks and that pressure in the filter is normal.

When cleaning the cartridges of a cartridge filter be sure to hose them off in a place that will not make a mess of the customer’s yard. They generally do not appreciate the mess and making a mess of the customer’s yard would be seen as unprofessional and careless.

Sand filters

Sand pool filter

Sand filters are commonly used for residential but even more commonly for commercial swimming pools in VA, MD or DC. Sand filters, in function work similarly to D.E. filters in that they can be backwashed, have backwash valves and should be backwashed about once per week. Sand filters are mostly if not always plastic or fiberglass.

When you are backwashing a sand filter, allow it to backwash for a couple of minutes, more so than you would with a D.E. filter. There is no powder or other filter media to add to a sand filter.

Inside a sand filter is a large compartment that holds fine sand. The water is pushed through this sand and the clean water is returned to the pool. The sand in this inner compartment collects the dirt and debris and serves as the filter media. Backwashing a sand filter once a week will blow much of this dirt and debris out of the sand and send it to the backwash line, just as it would with a D.E. filter.

Once every 3-5 years the sand inside a sand filter should be removed and replaced with new sand.

Things to remember about filters

  • There are three types of filters commonly in use for swimming pools and spas. They are D.E. or Diatomaceous Earth Filters, Cartridge Filters and Sand Filters.
  • Diatomaceous Earth filters are made up of a series of fine mesh grids with a plastic structure that are contained within a plastic, fiberglass or metal tank. These fine mesh grids hold on to the Diatomaceous Earth (D.E.) or also called filter powder which coats the grids. The D.E. powder is what actually does the filtering while the grid’s job is to hold the powder in place.
  • A D.E. filter can be back washed which flushes out most of (but not all) of the current D.E. powder, dirt and debris inside the filter so that you can replenish it with fresh new Diatomaceous Earth. This process reduces the filter pressure, cleans out much of the dirt and debris and allows for strong suction and return of the water.
  • Diatomaceous Earth is a carcinogen and can cause cancer. It is so fine that if breathed in it will remain in your lungs. Use CAUTION when handling!
  • Cartridge Filters are similar in shape and size to a D.E. filter and contain a simple fine mesh material or cloth like material cartridge inside the filter tank which collects the dirt and debris.
  • Cartridge filters do not require any special powder as the cartridge itself does the filtering.
  • Cartridge filters do not filter out debris quite as well as a D.E. filter but work well and will still be commonly found in the field.
  • When cleaning the cartridges of a cartridge filter, or any filter for that matter, be sure to hose them off in a place that will not make a mess of the customer’s yard. They generally do not appreciate the mess and making a mess of the customer’s yard would be seen as unprofessional and careless.
  • Sand filters are commonly used for residential but even more commonly for commercial swimming pools in VA, MD or DC. Sand filters, in function work similarly to D.E. filters in that they can be backwashed, have backwash valves and should be backwashed about once per week. Sand filters are mostly if not always plastic or fiberglass.
  • When you are backwashing a sand filter, allow it to backwash for a couple of minutes, more so than you would with a D.E. filter. There is no powder or other filter media to add to a sand filter.
  • Once every 3-5 years the sand inside a sand filter should be removed and replaced with new sand.

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