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Thread: How do I get a filter's nominal filtration rate data ?

  1. Back To Top    #1

    Join Date
    Apr 2008
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    Indonesia
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    How do I get a filter's nominal filtration rate data ?

    Hello All,

    I have some experience with diesel engine filtration system, where the final stage will remove about 2 microns. Its part of my work that I attend to these engines and its system.

    When I started to want to know about my pool filter system, I can't find any manufacturer data on their filter nominal filtration rate. I know there is no such thing as 100% filtration. Usually its 98% or around there. Some filters even specify Beta Ratio.

    I understand that water clarity when the chemical & sanitizing balance is good, its all about filtration and filtration means water circulation in a pool. Water circulation also broadcast the sanitizer well.

    I read that sand filter is anything from 60 to a 100 micron. This is why I am not happy at all with sand and installed a cartridge filter downstream the sand, knowing that cartridge filter is about 10-20 micron rating ( so they claimed ). The other reason for using this cartridge is because when vacuuming, I do not need to throw water...I can trap fine dirt with cartridge filter, but not the sand. So I am saving money on water actually and getting clearer water at the same time.

    I have wanted to use DE but since it has more maintenance, instead I chose natural volcanic Zeolite to replaced my sand, the brand is Zelbrite and the colour is red. While using Zeolite/Zelbrite, I realized that the 3-5 micron rating is probably not true, even though if it is true.... the way the sand filter works, the gaps between the zeolite will allow particles bigger than 3 microns to pass thru. So I suppose sand filter by its design ( stacking of sand grains ) has very low nonimal filtration rate...how much ...I don't know. All I know that my cartridge filter still get dirty ( but much slower though ) while being downstream of what is supposed to do a 3-5 micron rating.

    The result of using Zelbrite is good. I backwash much less. Water clarity is better than sand + cartridge. The Zelbrite is the last addition I made. The Zelbrite does all it said it will do fairly well, its just I am not able to define nominal filtration rate for sand filter replaced by Zelbrite media and for the cartridge.

    I use torchlight at night to test for suspended particles in my water, sort of turbidity test.

    If there is a cartridge filter if anyone knows, that can do 5 micron filtration, I would like to get one.
    I believe that for maximum clarity/visibility I must remove smaller particles that my cartridge can't.

    The pool is for dive training, so I realy like to see maximum water clarity. I am quite paranoid when my pool do not have sparkling water. All the divers wear mask, so they can immediately see if end to end at 36 feet of the pool is not clearly visible, then water is not good. I have very clear water and above average, but I am trying to get even better clarity if possible.

    Is it adviseable if I now install a DE downstream of my cartridge ? I am guessing that the DE will get clogged very slowly since there are 2 filters already upstream.

    When only sand was used, clean filter pressure was 5psi. When cartridge was added, the sand filter starts at 10 psi clean.
    The cartridge starts at 3-5 psi clean.

    Ted sticky on DE stated 8-20 psi clean filter pressure, assuming the worst at 20 psi and I buy a very big DE filter to reduce head loss, is it right if I calculate 10psi clean sand pressure will be raised to 30 psi worst case ?? If I start at 30 psi clean on the sand, that means 40 psi dirty and the sand filter housing is rated I think 50 psi....borderline.

    What are the typical clean pressure reading of DE for in ground pool and pump 3 feet above water line ?

    What is your advice on this DE addition guys ?

    Many thanks in advance.


    SPP
    35,000 GL pool. In Ground. Concrete with all white ceramic tiles. Outdoor but shaded.
    Approx 36 ft by 15 feet. 2HP Hayward Super Pump, Hayward Sand Filter with Zelbrite ( Zeolite ), Hayward Cartridge Filter, Aquamatic Silver+Copper Ionizer ( suspended use since Oct 2008 ), Prozone Ozonator, 2 gram/hr, Analog Flowmeter on pipe

    Back Up Pump & Filter on trolley, Pentair 1.5HP + Pentair Cartridge Filter, Slime Bag 1 micron Jumbo Size, downstream of Cartridge

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    I have never heard of anyone actually trying one, but there is a product called the Slime Bag that claims some amazing filtration ability.
    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
    Apr 2008
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    Indonesia
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    Thank you so much Jason. You are Magic !!!

    The Slime Bag will fit my back up pump& filter on trolley since I can float the Slime Bag in the pool.

    Slime bag biggest housing is expensive at US$1,550 and I don't have much permanent space anymore.

    Shipping such a bulky filter housing to Indonesia will cost at least US$800 if not more.


    The bag itself is cheap and worth the try. I will write to them.

    Many many thanks Jason.


    Regards,
    Surya
    35,000 GL pool. In Ground. Concrete with all white ceramic tiles. Outdoor but shaded.
    Approx 36 ft by 15 feet. 2HP Hayward Super Pump, Hayward Sand Filter with Zelbrite ( Zeolite ), Hayward Cartridge Filter, Aquamatic Silver+Copper Ionizer ( suspended use since Oct 2008 ), Prozone Ozonator, 2 gram/hr, Analog Flowmeter on pipe

    Back Up Pump & Filter on trolley, Pentair 1.5HP + Pentair Cartridge Filter, Slime Bag 1 micron Jumbo Size, downstream of Cartridge

  4. Back To Top    #4

    Join Date
    Mar 2007
    Location
    San Rafael, CA USA
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    12,085
    The only word of caution I would add is that part of the difficulty with filtration has to do with getting all of the water through the filter. I have a cartridge filter and the water clarity is excellent except for one problem. Oils tend to stay on the surface of the water so unless your flow rate is high enough to create a funnel suction effect in the skimmer, such oils will not get through to your filter, regardless of type. Though a scum ball or equivalent should help, I haven't found them to be fast enough to keep up with demand when the pool is used every day (i.e. suntan lotion gets in the pool faster than it can be removed).

    So look at the particles you see in the water and if it is mostly a surface film, then figure some way to skim that from the surface. Otherwise, if it's truly suspended particles in the water itself, then that's something a finer filter should handle.

    Also keep in mind that one can add some DE to a sand filter to get some DE clarity with the ease of backwashing, though you have to replace the DE after every backwash.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  5. Back To Top    #5

    Join Date
    Apr 2008
    Location
    Indonesia
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    311
    Hello Richard,

    Thanks for the info.
    My pool overflow the incoming water into a balancing tank of about 3,000 liter capacity, for rain and bather's water displacement.
    Since my pool is shaded and not a public pool but more of a special dive training only and not in use everyday, diver's don't usually use suntan lotion, since they are wearing wetsuit anyway.

    The scum line is obvious in my balancing tank....sort of black and also fine sendiment like dust from the air. Worse case scenario, I vacuum the balancing tank and set the water out to drain. So oil film is not an issue, the balancing tank helps.

    I use torchlight at night at 5-10" depth to check turbidity, its fine particle I am looking at.
    Let me study more of DE by talking to the local Pentair dealer, but I backwash my sand/zelbrite like once a month or twice if diver load is high. The cartridge, I wash at the extreem is 3 times a month when diver load is high. I can see increase of 2 psi easy a day if there are 5-6 divers spending 3 hours in the pool.

    If that Slime Back tested good with my portable trolley, I may buy suitable Pentair filter housing only and modified it to hold the Slime Bag. Space is a premium now, I may need to use two of cartridge filter housing, since its not fat like sand.

    Thanks again Richard, really appreciate.

    Surya
    35,000 GL pool. In Ground. Concrete with all white ceramic tiles. Outdoor but shaded.
    Approx 36 ft by 15 feet. 2HP Hayward Super Pump, Hayward Sand Filter with Zelbrite ( Zeolite ), Hayward Cartridge Filter, Aquamatic Silver+Copper Ionizer ( suspended use since Oct 2008 ), Prozone Ozonator, 2 gram/hr, Analog Flowmeter on pipe

    Back Up Pump & Filter on trolley, Pentair 1.5HP + Pentair Cartridge Filter, Slime Bag 1 micron Jumbo Size, downstream of Cartridge

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