Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 20 of 20

Thread: DE in sand filter

  1. Back To Top    #1

    Join Date
    Apr 2007
    Location
    Raleigh, NC
    Posts
    4

    DE in sand filter

    Since I found out about the BBB method from the other Pool Solutions Forum I have followed it religiously and it has worked great for 3 years. So I think I will follow suggestion from several folks and add a cup of DE to the sand filter. Do any of you pool owners in Raleigh NC know if Rising Sun carries DE or have suggestion where I might purchase? Thanks
    Pro pool installer for over 35 years
    Shadebuilder.com

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879
    Home Depot and Lowes both usually carry DE. Their pool departments are generally out near the plants, poorly stocked, and forget about asking for help, but the prices are good when they have what you want.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. Back To Top    #3

    Join Date
    May 2007
    Location
    virginia
    Posts
    25
    How does the DE help or work in a sand filter?
    36k, 23'x47' freeform 3.5'-9'deep
    Gunite/white plaster
    Colorlogic LED lights.

  4. Back To Top    #4
    DE can remove VERY tiny particles, adding that sparkly polish to your water. When you backwash, you have to replace the DE, as it sits atop your sand, and is so light it just floats out!

    When adding DE to a sand filter, it will probably take less than a cup. Add the DE very slowly (over the course of several hours?) through your skimmer until you get a 1psi rise in yout filter.

    8200 gallon 20' x 48" round vinyl frame pool, manually chlorinated with 10% liquid, salt added to ~2000, 12" sand filter, 1600gph pump, TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, Chlorine/CYA Chart
    "Shock" is a process, not a product!

  5. Back To Top    #5
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879
    Sand filters normally filter out particles down to about 20 or 25 microns. DE fitlers filter out particles down to 3 to 5 microns. By carefully adding a little DE to a sand filter you can partially clog up the pores in the sand giving you the 3-5 micron filtering, but you need to replace the DE every time you backwash. Getting the 5 to 25 micron particles, which would normally go right through a sand filter, out of the water give it a little extra clarity and sparkle. Some people refer to is as "polishing" the water.

    Basically you check the presure of the filter, mix half a cup of DE with water and pour it into the skimmer, repeat additions until your filter presure goes up 1 lb. Once you know how much DE your filter needs you can add all of it in one step the next time. One or two cups usually does it. Keep in mind that DE particles are really small (ie get into the air really easily) and you don't want to breathe them in, so wear a resperator of some kind. The ones they sell for wood workers ought to be good enough and are easy to find.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  6. Back To Top    #6

    Join Date
    May 2007
    Location
    virginia
    Posts
    25
    Thanks! I will keep this in mind. If all goes well, (putting together the correct equipment package) then I will be ordering a pool next monday. So this is definitely something to keep in mind.

    Again,
    Thanks!!
    Todd
    36k, 23'x47' freeform 3.5'-9'deep
    Gunite/white plaster
    Colorlogic LED lights.

  7. Back To Top    #7

    Join Date
    Apr 2007
    Location
    Raleigh, NC
    Posts
    4
    Many thanks for the detailed info on how to apply. I probably would have just dumped a cup in the skimmer.
    Pro pool installer for over 35 years
    Shadebuilder.com

  8. Back To Top    #8

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,078
    Just to stir the pot a little, I have a mild degree of skepticsim about adding DE to a sand filter. I have tried it on two occassions and could detect no difference. I have anecdotal evidence from two others who have tried it with no detectable difference.

    I realize many of you have done it with reported success but, somehow, the logic of it doesn't register with me. If the DE is fine enough to capture particles that pass thru sand, why doesn't the DE pass thru the sand as well? I admit to being inordinately skeptical but I wonder if any of the filter companies have ever done any research on this subject or if anyone has actually tested water clarity before and after DE?

    POOLGIRL, I'm in Raleigh and have not seen DE in Lowe's or HD (still may be there, tho).....it's in all the pool stores I have visited.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  9. Back To Top    #9

    Join Date
    Apr 2007
    Location
    Raleigh, NC
    Posts
    4
    Thanks for info DURALEIGH. I may just pass on the idea since I would have to go to pool store and I already owe for repair visit. But I had to laugh when I saw the word logic in your post. There is absolutely nothing logical about my pool. I am sure I am the only person that has had their pool turn the most beautiful shade of PURPLE (at Easter 3 years ago no less). The only thing that has kept me from losing my mind is that I learned the BBB method.
    Pro pool installer for over 35 years
    Shadebuilder.com

  10. Back To Top    #10
    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    Location
    SW Indiana
    Posts
    9,089
    Quote Originally Posted by duraleigh
    Just to stir the pot a little, I have a mild degree of skepticsim about adding DE to a sand filter. I have tried it on two occassions and could detect no difference. I have anecdotal evidence from two others who have tried it with no detectable difference.

    I realize many of you have done it with reported success but, somehow, the logic of it doesn't register with me. If the DE is fine enough to capture particles that pass thru sand, why doesn't the DE pass thru the sand as well?
    Median particle size for swimming pool DE is 34 microns, which is plenty large enough to be caught by the sand filter. Assuming nothing else special, adding a little DE will make your filter work better, like a slightly dirty filter. The physical characteristics of the DE, with many small particle grabbing pores would seem to make it even better than that. IF the DE coats the sand bed in a uniform layer, it would be little different than a DE filter in that the sand is a just like the grids in a DE filter.

    It would be interesting to add the DE to a sand filter, then to shut it down and remove the valve and see how the DE looks. I would suspect that it will not be in a layer, but rather at varying depths within the sand bed and not acting like a DE filter.

    I'll add for folks unfamiliar with sand filters that I don't add anything to my sand filter and it keeps my pool water crystal clear. I have cattle on one side and a corn field and gravel road on the other.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  11. Back To Top    #11
    KurtV's Avatar
    Join Date
    Mar 2007
    Location
    SE Louisiana
    Posts
    270
    Quote Originally Posted by JohnT
    ...

    It would be interesting to add the DE to a sand filter, then to shut it down and remove the valve and see how the DE looks. I would suspect that it will not be in a layer, but rather at varying depths within the sand bed and not acting like a DE filter.

    ...
    I've actually done that and it does indeed form a pretty uniform layer on the top of the sand (zeo in my case) bed.

  12. Back To Top    #12
    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    Location
    SW Indiana
    Posts
    9,089
    Quote Originally Posted by KurtV
    Quote Originally Posted by JohnT
    ...

    It would be interesting to add the DE to a sand filter, then to shut it down and remove the valve and see how the DE looks. I would suspect that it will not be in a layer, but rather at varying depths within the sand bed and not acting like a DE filter.

    ...
    I've actually done that and it does indeed form a pretty uniform layer on the top of the sand (zeo in my case) bed.
    Cool! Thanks for the info.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  13. Back To Top    #13
    TexasGirl's Avatar
    Join Date
    Apr 2007
    Location
    Central Texas
    Posts
    95
    DE can be purchased at both Lowes and Home Depot plus Leslie's in Central Texas.

    (31% Muriatic Acid, as well)
    Debbie

  14. Back To Top    #14
    Guest
    Clean sand will filter to about 60 microns. When it gets dirty it will filter to about 30 microns. Adding DE 'dirties' the filter and will not produce the 5-6 micron filtration a DE filter will since the DE can and will move between the sand particles. It will improve filter performance of a sand filter to a degree but it no way comes close to the filtration of a DE filter. Also, as sand ages and the facets on the sand become 'polished off' from the erosion of the constant flow of water it becomes less effective at catching particles and it's filtering ablility decreases. Sand's biggest plus is that it is the easiest type of filter to maintian. A cartridge will filter to about 20 microns clean and probably below 10 microns when it starts to get dirty and actually approaches DE's effectiveness at filtration, unless the cartridge has been acid washed. Acid washing a cartridge will cause the filter fabric to stretch and the pores in the material will become larger. (A cartridge is, IMHO, much easier to clean than a DE filter, which really should be broken down to be cleaned and not backwashed or bumped, but that is a topic for another thread!) The biggest drawack to a cartridge filter comes when they are undersized and the time between cleanings is very short, an all too common occurance! Also, as any filter dirties the flow rate will decrease which will make filtration less effective since it will take longer to filter the same amount of water so while you can increase the effectiveness in terms of size of particle filtered there is a diminishing return because it will take more time to filter and 'turnover' the water.

  15. Back To Top    #15

    Join Date
    Apr 2007
    Location
    East Tennessee
    Posts
    278
    Last year I was doing some microbiology experiments on the pool. One experiment included taking a volume of pool water and concreting it by centrifugation. The experiment took about 5 weeks. I was concretizing the pool water to increase the ability to catch any possible pathogens in the pool. I used 2-60 cc conical tubes and concreted the pool water. I removed the supernatant and cultured, wet mounted, and stained the remaining material. At week 3 I added the DE and found my testing material had be cut by greater than 50 %. Under the scope the particle size had also dropped. The scope I was using did not have a micrometer so I can’t give particle sizes. There are gains using DE in your sand filter but you must weigh them with the need to run your pump longer as WaterBear spoke of.
    BTW you don’t want to know what I grew in the water at the levels Nature 2 recommended at the time I bought my pool. Then again Nature 2 is one of my big rants.
    Steve
    Echo Canyon II by Artesian Pools, 13.5 KGal AG Round, 22" Artesian Sand Filter 2 hp Artesian pump
    Med Lab Tech for 12 years in E.TN
    Chem testing by Trouble Free Test Kits

  16. Back To Top    #16

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,078
    Quote Originally Posted by tpg
    How does the DE help or work in a sand filter?
    tpg,

    By now, are you sorry you asked???

    Seriously, I have enjoyed this thread and learned from it. My take from all this is, if you want absolutely the cleanest, most sparkling water in your town, adding a little DE might help and certainly doesn't hurt. However, dirty sand may just accomplish the same thing.

    Since the cost of dirty sand is cheap and DE, regardless how inexpensive, would have to come from my beer budget.......hmmmm.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  17. Back To Top    #17

    Join Date
    May 2007
    Location
    virginia
    Posts
    25
    Nope, I am not sorry in the least!

    It is something to think about though. I too have learned alot from this thread and am grateful for all that has been shared. Now I have read else where about people using "skimmer socks". How small of a particle do they capture?

    It has been fun and interesting to hear people discussion the differences in the capabilities of the different filters systems. As a wood worker, I know that the 3 micron filter bags on my dust collector has made a big difference when compared to the old 30 micron bags that I had. This is how I have visualize the differences in these filter systems.

    TPG
    36k, 23'x47' freeform 3.5'-9'deep
    Gunite/white plaster
    Colorlogic LED lights.

  18. Back To Top    #18
    Guest
    Quote Originally Posted by tpg
    Nope, I am not sorry in the least!

    It is something to think about though. I too have learned alot from this thread and am grateful for all that has been shared. Now I have read else where about people using "skimmer socks". How small of a particle do they capture?

    It has been fun and interesting to hear people discussion the differences in the capabilities of the different filters systems. As a wood worker, I know that the 3 micron filter bags on my dust collector has made a big difference when compared to the old 30 micron bags that I had. This is how I have visualize the differences in these filter systems.

    TPG
    Skimmer socks don't really trap the small stuff but they are great for keeping the bigger stuff out of your filter and they really do lengthen the time between filter cleanings. I have been using them for a few years and they are one inexpensive pool gadget that is really worth ten times the price that they cost!
    During pollen season they are easily worth one hundred times the price!
    The way you visualize the dfference in filter systems is entirely correct. The only difference is that yours are filtering particles out of the air and your pool's are filtering particles out of the water.

  19. Back To Top    #19
    KurtV's Avatar
    Join Date
    Mar 2007
    Location
    SE Louisiana
    Posts
    270
    Quote Originally Posted by waterbear
    Clean sand will filter to about 60 microns. When it gets dirty it will filter to about 30 microns.
    Most of what I've read claims sand will filter particles as small as 20-30 microns, cartridges 5-10, and DE 3-5. I don't have the ability or inclination to test that though.

    Adding DE 'dirties' the filter and will not produce the 5-6 micron filtration a DE filter will since the DE can and will move between the sand particles.
    In my experience, I have seen the DE coat the top of the sand bed down to a very shallow depth (maybe as deep as 5mm) and not move any further through the sand.

    It will improve filter performance of a sand filter to a degree but it no way comes close to the filtration of a DE filter.
    I wouldn't claim that it it equates to a DE filter because I just don't know. Intuitively though, it seems that it would get close.

    Also, as sand ages and the facets on the sand become 'polished off' from the erosion of the constant flow of water it becomes less effective at catching particles and it's filtering ablility decreases. Sand's biggest plus is that it is the easiest type of filter to maintian. A cartridge will filter to about 20 microns clean and probably below 10 microns when it starts to get dirty and actually approaches DE's effectiveness at filtration, unless the cartridge has been acid washed. Acid washing a cartridge will cause the filter fabric to stretch and the pores in the material will become larger. (A cartridge is, IMHO, much easier to clean than a DE filter, which really should be broken down to be cleaned and not backwashed or bumped, but that is a topic for another thread!) The biggest drawack to a cartridge filter comes when they are undersized and the time between cleanings is very short, an all too common occurance! Also, as any filter dirties the flow rate will decrease which will make filtration less effective since it will take longer to filter the same amount of water so while you can increase the effectiveness in terms of size of particle filtered there is a diminishing return because it will take more time to filter and 'turnover' the water.
    Will the flow actually decrease? Won't the increased resistance be overcome by the increased pressure? (E=IR in electricity is roughly analogous, no?)
    I would add life cycle cost to the advantages of sand filters. Cartridges ain't cheap and need to be replaced periodically. DE is an ongoing, regular cost.

  20. Back To Top    #20
    Guest
    Quote Originally Posted by KurtV
    Quote Originally Posted by waterbear
    Clean sand will filter to about 60 microns. When it gets dirty it will filter to about 30 microns.
    Most of what I've read claims sand will filter particles as small as 20-30 microns, cartridges 5-10, and DE 3-5. I don't have the ability or inclination to test that though.
    And those claims are not wrong either. New sand that has not smoothed off and is slightly dirty might actually be able to trap particles that are as small as 20 microns. Old sand that is polished probably won't get anything smaller than about 60 microns when it is freshly backwashed. The Reemay polyester material that carts are made out of is usually rated at 20 microns but when it gets dirty and the pores start to get plugged it will filter out much smaller particles and beings to approach DE in effectiveness. DE will filter to about 5 microns but , once again, when dirty can go a bit smaller but this is self limiting because it clogs so easily and then your pressure rises, filtration becomes less effective, and you have to clean the filter so this is more self limiting.
    Adding DE 'dirties' the filter and will not produce the 5-6 micron filtration a DE filter will since the DE can and will move between the sand particles.
    In my experience, I have seen the DE coat the top of the sand bed down to a very shallow depth (maybe as deep as 5mm) and not move any further through the sand.
    Much of the DE will sit on top of the sand but unless you actually stir up the sand bed and look you really don't know how much is between the grains. Also the fact that much of the DE is sitting on top means that it can be disturbed and that larger particles can get past it. You are putting MUCH less DE into a sand filter than you would in a DE filter so the filtering depth of the DE is going to be much less and therefore it's filtering ability much less.
    It will improve filter performance of a sand filter to a degree but it no way comes close to the filtration of a DE filter.
    I wouldn't claim that it it equates to a DE filter because I just don't know. Intuitively though, it seems that it would get close.
    IMHO, you would see a greater benefit with older sand when you add DE. In fact, most of the people who swear by DE in a sand filter are the same ones who say you never have to change your filter sand! (If you've read the threads at PoolForum you know what I'm talking about.)
    Also, as sand ages and the facets on the sand become 'polished off' from the erosion of the constant flow of water it becomes less effective at catching particles and it's filtering ability decreases. Sand's biggest plus is that it is the easiest type of filter to maintain. A cartridge will filter to about 20 microns clean and probably below 10 microns when it starts to get dirty and actually approaches DE's effectiveness at filtration, unless the cartridge has been acid washed. Acid washing a cartridge will cause the filter fabric to stretch and the pores in the material will become larger. (A cartridge is, IMHO, much easier to clean than a DE filter, which really should be broken down to be cleaned and not backwashed or bumped, but that is a topic for another thread!) The biggest drawback to a cartridge filter comes when they are undersized and the time between cleanings is very short, an all too common occurrence! Also, as any filter dirties the flow rate will decrease which will make filtration less effective since it will take longer to filter the same amount of water so while you can increase the effectiveness in terms of size of particle filtered there is a diminishing return because it will take more time to filter and 'turnover' the water.
    Will the flow actually decrease? Won't the increased resistance be overcome by the increased pressure? (E=IR in electricity is roughly analogous, no?)
    What the filter gauge is measuring is backpressure that is working against your pump
    I would add life cycle cost to the advantages of sand filters. Cartridges ain't cheap and need to be replaced periodically. DE is an ongoing, regular cost.
    When properly maintained a cartridge can last for 5-7 years. If it costs $100 that works out to $20 a year or less. Sand also needs to be replaced (I know this is an ongoing debate but look at new sand under a microscope and look at old sand and tell me which one you think will filter better, Much of the improved filtration ability of Zeolite is not because it has pores but because it is much rougher than sand so it can trap particles easier) Sand might actually only have a lifespan of about 3 years if the pool has an extended swim season and is not winterized, making sand about as costly as cartridge.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •