High pressure, as measured by the gauge atop your filter is not a good thing. It does not represent good water flow, just the opposite: high pressure indicates increased restriction to the flow of water. When the filter's pressure is substantially higher than it was when you last backwashed,then it is time to backwash again or to perform a clean out. Sometimes, the clean pressure of a swimming pool's filter will be as low as 5 to 6 pounds per square inch (psi), other filters may range up to 20 psi or more, clean pressure. It just depends on a pool's particular configuration. The power of the pump, the size of the plumbing, the size, type of filter, the water inlet/outlet orifice size, the distance the pool is from the equipment, and any add ons like suction or pressure side cleaners, all influence the PSI as read from the filter's pressure gauge. All of these items have an impact upon what the pressure will be.
How are you to determine when the pressure has risen high enough, to cause you to backwash or clean the filter? There are several different ways of determining this. The first is when you notice that the "action" on the pool's surface is beginning to slow down, you may notice for instance that the inlet jets don't seem to be pushing the water as far as before, or perhaps the skimming action has slowed down.
Another way is to put your fingers into the suction line, at the bottom of the skimmer's housing. If your fingers feel like they are going to be snatched off your hand, then the filter can probably go without being serviced yet. If there is not much of a pull on your fingers, then its' time for servicing.
You may notice also, that your suction side or pressure side cleaner doesn't climb the walls as well as before, or starts to let dirt accumulate around the bottom of the pool. Also if you vacuum manually, you may notice that the suction has dropped off and dirt is not being pulled up into the vacuum hose as vigorously as before. Sometimes, if the filter is really plugged, any additional dirt added to it will cause the dirt to just go right on through and and back into the pool via the inlet jets, then you will see the dirt being put back into the pool.
If any of these situations develop, it is time to take a look at the filters pressure gauge. Most of the time you will see that the pressure gauge is 6 to 15 psi over what it was when the filter was clean. As the dirt, dust and debris accumulate within the filter, the pressure will increase and will be measured by the pressure guage in pounds per square psi. Generally, you will not want to wait until the pressure is really high. So don't wait too long. Over time you will learn at what psi pressure to backwash or clean your filter
.
Wednesday, July 20, 2011
Monday, July 18, 2011
Diatomaceous Earth Filters, Disadvantages :
The first and probably greatest disadvantage to owning a pool with a DE filter is that is not trivial to maintain, in other words, as compared to a sand filter, the DE filter is a high maintenance item. This maintenance issue can be broken down and organized into the following two sections.
Maintenance issue # 1 :
Elaborate Backwashing and Recharging Techniques
The DE filter, like the sand filter, can be backwashed to clean it out. However, this backwashing effort is different. The DE filter must be backwashed three times in a row to remove most of the old DE media. You have to turn the pool pump off. Move the backwash valve into the proper position, and turn the pump back on. At this point, the water flow inside of the filter will reverse direction, washing the filter grids clean of the old DE powder. This dirty powder will then leave the filter and travel down the backwash pipe or hose and exit into a pit or perhaps the lawn.
Once the backwash water has turned clear, you turn the pump off and move the backwash valve back into it's original position. Turn the pool pump back on. The pump will now push water back into the filter and whatever old DE powder that remains in the filter will begin to collect again on the grids. Wait for five minutes, turn the pump off, move the backwash valve back into the "backwash position", and turn the pump back on. This time the water from the filter will still be dirty, but won't take as long to clear. This process needs to be repeated one more time, for a total of three backwashes. You will notice that the during the last backwash, just a little puff of dirt will exit. Whew!....But we aren't done yet!
You have to get the bag of DE powder, the one you bought at your local pool store. Oh! I forgot to tell you about that. You need to buy DE powder for this type of filter. Well, at least it is cheap. Also, pick up some good dust masks to wear while you are working with this powder.
According to your DE Filters manual and following the instructions on the reverse side of the bag of DE, you will measure out and use at least several coffee cans worth of DE powder to do what is called "recharging" the filter. Note: There is a specially made plastic scooper that holds one pound of DE powder. Pick one up at your local pool store.
This " recharging" is accomplished by mixing the prescribed number of cans of DE powder into a five gallon bucket, filled with water. With the pool pump running, take the skimmer lid off, lift out the skimmer basket, and the diverter valve. Then slowly pour this mixture into the skimmer. A shortcut that I have used is to just put the cans of DE powder, one at a time, directly into the skimmer, while the pool pump is running. Be aware that this shortcut really makes a mess, and you better be wearing the dust mask during the whole process, from start to finish, because there will a lot of dust in the air. The mixture will flow through the pools suction line, back towards and through the pump, and once again collect onto the septum of the filter grids. You now have a new and clean DE filter media for your pool water to flow through....
Unfortunately, not all of the old DE powder has gotten out of the filter! It never does. When you backwash a DE filter, there is always some left behind. You can get by with backwashing a DE filter perhaps three times over the course of a year or more, depending on the weather. After that, guess what? You have to disassemble the DE filter and clean it out by hand. Oh! Joy of Joys!
This disassembling process is quite involved and it is at this point where mere words fail. I will have to create a video and provide detailed instructions, or provide a link to a youtube video at this point. For now, just do a Google video search for cleaning out DE filters and you will probably find something to look at. I will talk about this manual clean out process in a later post.
There are a series of warnings in connection with diatomaceous earth powder, that I feel a need to talk about:
DE powder scatters like a fog when disturbed, and rises into the air with very little wind. Do not allow anyone to be close to you as you are working with this powder! As you fill your can or scooper with DE powder, the powder will float in the air around you. So be sure you are using your face mask. A lot of people, including professionals, try to get around the wearing of a dust mask. They get the bright idea to just hold their breath. I too have tried to skip wearing a dust mask. Sooner or later you will screw up and draw air filled with DE powder into your lungs. Twice, I have spent several days coughing and spitting up white DE powder. Guess what? You can't get all of this stuff out of your lungs. It stays in there for the rest of your life and fuses with your lung tissue. Use a dust mask.
Do I need to warn you against leaving the partially empty DE powder bag around where children might have access to it? Yes, I do. Put the bag high up on a shelf, preferably with a bunji cord wrapped around it. Warn your children or grandchildren to stay away from this stuff.
Maintenance issue # 2 :
Fragile Internal Frame and Grid Work
The second big disadvantage to owning a DE filter is that the internal plastic grid work, and the grid work's septum are fragile and they just don't last nearly as long as the internal parts of a sand filter. The grids, themselves, when viewed from above are designed in a spiral pattern to maximize filter area within a confined space. It is not uncommon that after as little as two years, during a clean out, you may notice a tear or a hole in the fabric of the septum of one or more of the grids. The ribs of the septum frame may also be broken. Any grids that have these defects are going to have to be replaced. Any twigs that get into a DE filter may puncture the septum, and that small puncture expands into a hole. If you neglect regular backwashing of your DE filter, the grid work will tend to break or be crushed. If you neglect cleaning out your filter, "bridging" between grids may occur, this increases the pressure on the grid frame and can break it.
So, with all of the previous information, it seems that a DE filter is a real pain, and it is. Do I still recommend this type of filter? Yes! I will still recommend a DE filter to anyone who is not afraid of learning something new, who is not afraid of getting their hands dirty or to someone who is not afraid of paying someone else to do the dirty work. It is just that a DE filter does such a very, very good job at filtering your pools water, that all the hassle is worth it. Ask anyone who owns one.
The next post will cover filter pressures.
Maintenance issue # 1 :
Elaborate Backwashing and Recharging Techniques
The DE filter, like the sand filter, can be backwashed to clean it out. However, this backwashing effort is different. The DE filter must be backwashed three times in a row to remove most of the old DE media. You have to turn the pool pump off. Move the backwash valve into the proper position, and turn the pump back on. At this point, the water flow inside of the filter will reverse direction, washing the filter grids clean of the old DE powder. This dirty powder will then leave the filter and travel down the backwash pipe or hose and exit into a pit or perhaps the lawn.
Once the backwash water has turned clear, you turn the pump off and move the backwash valve back into it's original position. Turn the pool pump back on. The pump will now push water back into the filter and whatever old DE powder that remains in the filter will begin to collect again on the grids. Wait for five minutes, turn the pump off, move the backwash valve back into the "backwash position", and turn the pump back on. This time the water from the filter will still be dirty, but won't take as long to clear. This process needs to be repeated one more time, for a total of three backwashes. You will notice that the during the last backwash, just a little puff of dirt will exit. Whew!....But we aren't done yet!
You have to get the bag of DE powder, the one you bought at your local pool store. Oh! I forgot to tell you about that. You need to buy DE powder for this type of filter. Well, at least it is cheap. Also, pick up some good dust masks to wear while you are working with this powder.
According to your DE Filters manual and following the instructions on the reverse side of the bag of DE, you will measure out and use at least several coffee cans worth of DE powder to do what is called "recharging" the filter. Note: There is a specially made plastic scooper that holds one pound of DE powder. Pick one up at your local pool store.
This " recharging" is accomplished by mixing the prescribed number of cans of DE powder into a five gallon bucket, filled with water. With the pool pump running, take the skimmer lid off, lift out the skimmer basket, and the diverter valve. Then slowly pour this mixture into the skimmer. A shortcut that I have used is to just put the cans of DE powder, one at a time, directly into the skimmer, while the pool pump is running. Be aware that this shortcut really makes a mess, and you better be wearing the dust mask during the whole process, from start to finish, because there will a lot of dust in the air. The mixture will flow through the pools suction line, back towards and through the pump, and once again collect onto the septum of the filter grids. You now have a new and clean DE filter media for your pool water to flow through....
Unfortunately, not all of the old DE powder has gotten out of the filter! It never does. When you backwash a DE filter, there is always some left behind. You can get by with backwashing a DE filter perhaps three times over the course of a year or more, depending on the weather. After that, guess what? You have to disassemble the DE filter and clean it out by hand. Oh! Joy of Joys!
This disassembling process is quite involved and it is at this point where mere words fail. I will have to create a video and provide detailed instructions, or provide a link to a youtube video at this point. For now, just do a Google video search for cleaning out DE filters and you will probably find something to look at. I will talk about this manual clean out process in a later post.
There are a series of warnings in connection with diatomaceous earth powder, that I feel a need to talk about:
DE powder scatters like a fog when disturbed, and rises into the air with very little wind. Do not allow anyone to be close to you as you are working with this powder! As you fill your can or scooper with DE powder, the powder will float in the air around you. So be sure you are using your face mask. A lot of people, including professionals, try to get around the wearing of a dust mask. They get the bright idea to just hold their breath. I too have tried to skip wearing a dust mask. Sooner or later you will screw up and draw air filled with DE powder into your lungs. Twice, I have spent several days coughing and spitting up white DE powder. Guess what? You can't get all of this stuff out of your lungs. It stays in there for the rest of your life and fuses with your lung tissue. Use a dust mask.
Do I need to warn you against leaving the partially empty DE powder bag around where children might have access to it? Yes, I do. Put the bag high up on a shelf, preferably with a bunji cord wrapped around it. Warn your children or grandchildren to stay away from this stuff.
Maintenance issue # 2 :
Fragile Internal Frame and Grid Work
The second big disadvantage to owning a DE filter is that the internal plastic grid work, and the grid work's septum are fragile and they just don't last nearly as long as the internal parts of a sand filter. The grids, themselves, when viewed from above are designed in a spiral pattern to maximize filter area within a confined space. It is not uncommon that after as little as two years, during a clean out, you may notice a tear or a hole in the fabric of the septum of one or more of the grids. The ribs of the septum frame may also be broken. Any grids that have these defects are going to have to be replaced. Any twigs that get into a DE filter may puncture the septum, and that small puncture expands into a hole. If you neglect regular backwashing of your DE filter, the grid work will tend to break or be crushed. If you neglect cleaning out your filter, "bridging" between grids may occur, this increases the pressure on the grid frame and can break it.
So, with all of the previous information, it seems that a DE filter is a real pain, and it is. Do I still recommend this type of filter? Yes! I will still recommend a DE filter to anyone who is not afraid of learning something new, who is not afraid of getting their hands dirty or to someone who is not afraid of paying someone else to do the dirty work. It is just that a DE filter does such a very, very good job at filtering your pools water, that all the hassle is worth it. Ask anyone who owns one.
The next post will cover filter pressures.
Sunday, July 17, 2011
Diatomaceous Earth Filters - Advantages
The last filter that I want to talk about is the diatomaceous earth (DE) filter. This filter type is the filter that is going to give you the most bang for your buck. The filter media here is diatomaceous earth, whereas in the cartridge filter the media is a glorified polyester paper, in the sand filter it is the sand that is the filtering media. When a DE filter is installed, the last part of the process is to add the DE powder by way of the skimmer. This "powder" is made up of many millions of skeletons of a microscopic animal called a diatom. This powder is mined from various deposits around the world.
Diatomaceous earth powder, when introduced into the skimmer, while the pump is on, flows with the water into the filter. As the DE powder enters the filter it encounters an internal structure called the "septum". This is a cloth like plastic platform which is supported by a plastic framework. You keep adding DE to the pools skimmer as directed by the DE filters owners manual. The powder collects upon this septum to a depth of about 1/2 inch. Once the DE powder has been added to the filter it usually adheres to the septum even when the pump turns off.
When the pool pump is operating , swimming pool water will flow through this layer of DE. Through a straining process, the pool water will leave behind particles of dust, dirt and debris on the surface and the inside of this layer. The water will continue to flow through the DE and then through the septum, returning to the pool cleansed.
This DE filter media will remove particles down to 3 microns, and this it will do immediately, right from the start, no other filter can do this as quickly or as economically. You can perform the following test: At night, turn on the pool light of a pool that has a DE filter. If the filter has been running sufficiently, then as you look into the beam of light you will notice no dust, just a crystalline clarity. If you do the same with a cartridge or a sand filtered pool, you will see a lot of stuff floating around within the beam of light. This stuff just blows right on through a cartridge or sand filter, over and over again without a chance of leaving the pool.
Advantages of a Diatomaceous Earth Filter:
1. The DE filter has the ability to immediately filter out particles down to 3 microns or less.
2. Your pool will have unparalleled clarity, due to advantage number one.
3. The old filter media is completely replaced every time you backwash and recharge the DE filter.
4. Algae, if it starts to grow, gets trapped initially in the total darkness of the filter. Where
there is no light, and therefore no growth. This gives you a little time to add some more
chlorine.
5. Bacteria, if present in the pool water has much less organic debris to feed upon.
6. You will have longer cycles between backwashings, because of the larger filtering area.
DE filters come in 24, 36, and 48 square foot or larger sizes. This greater filter area means that you will not have to backwash a DE filter as often as a sand filter. Sand filters in contrast, come in 3.1, 4.8, and 6.4 square foot or larger sizes. This crimps the dirt load carrying capacity of sand filters, although it is trivial to backwash them.
I had a lady call me out to a repair call on a DE filter that I had installed about a year earlier. It was a smaller 24 square foot model. What I discovered is that she had not backwashed nor cleaned out that filter in a years time! All of the internal grids were crushed! She acknowledged that I had explained to her the maintenance procedures, and that I was available to do the work, but she explained that she just never got around to it. But, that small filter did last one year, which shows you the DE filter's dirt carrying capacity.
There is an old argument between pool professionals as to what is best to install on a pool, a sand or a DE filter, I prefer the DE filter. One professional said to me "What are you talking about? All they are going to do is swim in the pool, not drink from it!"
You know, he is correct, but lets put it this way: Which pool do you want your children or grandchildren to be swimming in? I want my grandkids to be swimming in water that has been filtered and sanitized to the greatest extent humanly possible and that is what a DE filter delivers. That is why I prefer to install DE filters. In the next post we will discuss some of the disadvantages of owning a DE filter.
Diatomaceous earth powder, when introduced into the skimmer, while the pump is on, flows with the water into the filter. As the DE powder enters the filter it encounters an internal structure called the "septum". This is a cloth like plastic platform which is supported by a plastic framework. You keep adding DE to the pools skimmer as directed by the DE filters owners manual. The powder collects upon this septum to a depth of about 1/2 inch. Once the DE powder has been added to the filter it usually adheres to the septum even when the pump turns off.
When the pool pump is operating , swimming pool water will flow through this layer of DE. Through a straining process, the pool water will leave behind particles of dust, dirt and debris on the surface and the inside of this layer. The water will continue to flow through the DE and then through the septum, returning to the pool cleansed.
This DE filter media will remove particles down to 3 microns, and this it will do immediately, right from the start, no other filter can do this as quickly or as economically. You can perform the following test: At night, turn on the pool light of a pool that has a DE filter. If the filter has been running sufficiently, then as you look into the beam of light you will notice no dust, just a crystalline clarity. If you do the same with a cartridge or a sand filtered pool, you will see a lot of stuff floating around within the beam of light. This stuff just blows right on through a cartridge or sand filter, over and over again without a chance of leaving the pool.
Advantages of a Diatomaceous Earth Filter:
1. The DE filter has the ability to immediately filter out particles down to 3 microns or less.
2. Your pool will have unparalleled clarity, due to advantage number one.
3. The old filter media is completely replaced every time you backwash and recharge the DE filter.
4. Algae, if it starts to grow, gets trapped initially in the total darkness of the filter. Where
there is no light, and therefore no growth. This gives you a little time to add some more
chlorine.
5. Bacteria, if present in the pool water has much less organic debris to feed upon.
6. You will have longer cycles between backwashings, because of the larger filtering area.
DE filters come in 24, 36, and 48 square foot or larger sizes. This greater filter area means that you will not have to backwash a DE filter as often as a sand filter. Sand filters in contrast, come in 3.1, 4.8, and 6.4 square foot or larger sizes. This crimps the dirt load carrying capacity of sand filters, although it is trivial to backwash them.
I had a lady call me out to a repair call on a DE filter that I had installed about a year earlier. It was a smaller 24 square foot model. What I discovered is that she had not backwashed nor cleaned out that filter in a years time! All of the internal grids were crushed! She acknowledged that I had explained to her the maintenance procedures, and that I was available to do the work, but she explained that she just never got around to it. But, that small filter did last one year, which shows you the DE filter's dirt carrying capacity.
There is an old argument between pool professionals as to what is best to install on a pool, a sand or a DE filter, I prefer the DE filter. One professional said to me "What are you talking about? All they are going to do is swim in the pool, not drink from it!"
You know, he is correct, but lets put it this way: Which pool do you want your children or grandchildren to be swimming in? I want my grandkids to be swimming in water that has been filtered and sanitized to the greatest extent humanly possible and that is what a DE filter delivers. That is why I prefer to install DE filters. In the next post we will discuss some of the disadvantages of owning a DE filter.
Sand Filters
History:
Sand filtration has a long history, the earliest recorded use of sand filtration was around 4000 B.C., in India. During the Roman Republic and during the Roman Empire, municipal water systems used sand filtration to treat the water before it was distributed locally. More recently, in mid 19th Century London, it was noted that in the local area around water pumps where sand water filters had been installed, the prevalence of cholera decreased. This led the British government to install sand filters everywhere water was drawn. In the United States, a rapid sand filter was developed, one that could be quickly cleaned with streams of water.
The Popular Sand Filter:
Within the context of swimming pools, in Maricopa County, the sand filter is by far the most common filter used. There are several reasons for this. One, they are reasonably priced due to a simple design and construction. Two, they are end user friendly. Three, they perform well enough for its intended purpose. Four, they have a long life and five, they are very easy to clean. These advantages really add up, and make the sand filter probably the best all round filter.
Cleaning or Backwashing the Sand Filter:
When the desert dust storms begin in July, the sand filter can quickly remove the dirt, dust, and debris that blows into the pool. Once the filter is full, backwashing really is a snap: turning the pump off, move the backwash valve handle into the backwash position. Then turn the pump back on. During the backwashing process, the flow of water within the sand filter is reversed. The water now enters the filter from the bottom, flowing upward through the sand and lifting the dirt up from the interior and the surface of the sand bed. The now dirty water flows out of the sand filter into a backwash pipe of hose usually into a specially made rock pit or just onto the lawn.
During this process, keep an eye on the water exiting the backwash pipe or hose. When the water
turns from dirty to clear, you can turn the pump off, and move the backwash valve handle back into it's original filtering position. Then start up the pool pump. If you are picky, you can run your pump for a few minutes and then repeat the process and a little more dirt will come out. It doesn't get any easier than this. This procedure can be followed for years without any extra maintenance to the filter.
WARNINGS:
WARNING # 1 : Do not backwash your sand filter too often. A sand filter removes smaller and smaller particles as the filter becomes dirty - in other words it becomes a better filter when it is allowed to dirty up some. Now, here you want to keep an eye on the pressure gauge. Let the pressure build up over time, It is OK! When finally, the circulation to the pool begins to slow down, and the pressure gauge reading gets high, then backwash.
I read an article years ago about an individual who did his masters thesis dissertation on sand filters. He found that a large sand filter when coupled with a high head pump could, (when allowed to get dirty, really plugged), filter particulates down to the size of 1/4th of a micron! He stated in the article that there was a lot of 1/4th of a micron stuff in the filter he studied. This what is called micro-filtration, which will catch algae, bacteria and protozoa. So let's remember not to backwash a sand filter too often.
WARNING # 2 : The sand filter uses a special type of sand media whose grains have many sharp points. It is these points that capture the particles of dust, dirt and debris that pass by. As the years go by, these points get worn down. Then the sand will need to be replaced, but not by any old sand, it has to be sand made in a special way, exclusively for sand filtration. In other words, don't put ordinary sand in the filter, go to the local pool store and buy a few bags.
Situations where the sand grains have worn down and become rounded, will not happen for five, ten or more years. In fact, I have seen thirty year old sand filters that are still functional. You can expect a long service life from this type of filter.
WARNING # 3 : Do not under any circumstances set the sand filter to the backwash position during the vacuuming of the pool or while the suction side cleaner is running - all the smaller debris will pass through the pump strainer basket and be deposited within the sand filters laterals which are at the bottom of the filter, and any dirt exiting the laterals will be deposited at the bottom of the sand bed. This is the reverse of the intended design! It is difficult to get dirt and debris out of these two areas of the filter.
WARNING # 4 : Keep your head and arms away from the top of any filter that is starting to get water from the pump. I have seen from time to time a gate valve installed on the backwash line. Usually it was installed there by someone trying to stop a leaking backwash valve. This is a bad thing to do! I remember trying to backwash a sand filter and because there was a gate valve on the backwash line, in the closed position, as I turned on the pump, the residue air in the filter was compressed by the water, which did not have anywhere to go. Remember that air compresses, water does not. The top lid of the filter blew off about 75 feet into the air. If I had my face or hands in the area of that lid, I would have been injured. So always check to be sure that the backwash pipe is free of gate valves. Always check to be sure that all of the gate valves are open on the lines returning to the pool. Children like to turn valves. If there are any other problems downstream from the filter, the same thing can happen. Remember don't lean or reach over the top of any filter while it is filling with water. In fact, avoid leaning over a pressurized filter at any time.
After turning the pool pump on, always slowly loosen the air relief valve to allow any air trapped in the filter to escape. This valve will usually be located under the pressure gauge. When all the air has been released and water comes out of the valve, close it back up.
The next post will cover the advantages of diatomaceous earth filters.
Sand filtration has a long history, the earliest recorded use of sand filtration was around 4000 B.C., in India. During the Roman Republic and during the Roman Empire, municipal water systems used sand filtration to treat the water before it was distributed locally. More recently, in mid 19th Century London, it was noted that in the local area around water pumps where sand water filters had been installed, the prevalence of cholera decreased. This led the British government to install sand filters everywhere water was drawn. In the United States, a rapid sand filter was developed, one that could be quickly cleaned with streams of water.
The Popular Sand Filter:
Within the context of swimming pools, in Maricopa County, the sand filter is by far the most common filter used. There are several reasons for this. One, they are reasonably priced due to a simple design and construction. Two, they are end user friendly. Three, they perform well enough for its intended purpose. Four, they have a long life and five, they are very easy to clean. These advantages really add up, and make the sand filter probably the best all round filter.
Cleaning or Backwashing the Sand Filter:
When the desert dust storms begin in July, the sand filter can quickly remove the dirt, dust, and debris that blows into the pool. Once the filter is full, backwashing really is a snap: turning the pump off, move the backwash valve handle into the backwash position. Then turn the pump back on. During the backwashing process, the flow of water within the sand filter is reversed. The water now enters the filter from the bottom, flowing upward through the sand and lifting the dirt up from the interior and the surface of the sand bed. The now dirty water flows out of the sand filter into a backwash pipe of hose usually into a specially made rock pit or just onto the lawn.
During this process, keep an eye on the water exiting the backwash pipe or hose. When the water
turns from dirty to clear, you can turn the pump off, and move the backwash valve handle back into it's original filtering position. Then start up the pool pump. If you are picky, you can run your pump for a few minutes and then repeat the process and a little more dirt will come out. It doesn't get any easier than this. This procedure can be followed for years without any extra maintenance to the filter.
WARNINGS:
WARNING # 1 : Do not backwash your sand filter too often. A sand filter removes smaller and smaller particles as the filter becomes dirty - in other words it becomes a better filter when it is allowed to dirty up some. Now, here you want to keep an eye on the pressure gauge. Let the pressure build up over time, It is OK! When finally, the circulation to the pool begins to slow down, and the pressure gauge reading gets high, then backwash.
I read an article years ago about an individual who did his masters thesis dissertation on sand filters. He found that a large sand filter when coupled with a high head pump could, (when allowed to get dirty, really plugged), filter particulates down to the size of 1/4th of a micron! He stated in the article that there was a lot of 1/4th of a micron stuff in the filter he studied. This what is called micro-filtration, which will catch algae, bacteria and protozoa. So let's remember not to backwash a sand filter too often.
WARNING # 2 : The sand filter uses a special type of sand media whose grains have many sharp points. It is these points that capture the particles of dust, dirt and debris that pass by. As the years go by, these points get worn down. Then the sand will need to be replaced, but not by any old sand, it has to be sand made in a special way, exclusively for sand filtration. In other words, don't put ordinary sand in the filter, go to the local pool store and buy a few bags.
Situations where the sand grains have worn down and become rounded, will not happen for five, ten or more years. In fact, I have seen thirty year old sand filters that are still functional. You can expect a long service life from this type of filter.
WARNING # 3 : Do not under any circumstances set the sand filter to the backwash position during the vacuuming of the pool or while the suction side cleaner is running - all the smaller debris will pass through the pump strainer basket and be deposited within the sand filters laterals which are at the bottom of the filter, and any dirt exiting the laterals will be deposited at the bottom of the sand bed. This is the reverse of the intended design! It is difficult to get dirt and debris out of these two areas of the filter.
WARNING # 4 : Keep your head and arms away from the top of any filter that is starting to get water from the pump. I have seen from time to time a gate valve installed on the backwash line. Usually it was installed there by someone trying to stop a leaking backwash valve. This is a bad thing to do! I remember trying to backwash a sand filter and because there was a gate valve on the backwash line, in the closed position, as I turned on the pump, the residue air in the filter was compressed by the water, which did not have anywhere to go. Remember that air compresses, water does not. The top lid of the filter blew off about 75 feet into the air. If I had my face or hands in the area of that lid, I would have been injured. So always check to be sure that the backwash pipe is free of gate valves. Always check to be sure that all of the gate valves are open on the lines returning to the pool. Children like to turn valves. If there are any other problems downstream from the filter, the same thing can happen. Remember don't lean or reach over the top of any filter while it is filling with water. In fact, avoid leaning over a pressurized filter at any time.
After turning the pool pump on, always slowly loosen the air relief valve to allow any air trapped in the filter to escape. This valve will usually be located under the pressure gauge. When all the air has been released and water comes out of the valve, close it back up.
The next post will cover the advantages of diatomaceous earth filters.
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