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Thread: Centaur Carbon Filter ?'s

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    DIY Junior Member JohnF10's Avatar
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    Question Centaur Carbon Filter ?'s

    Newbie here with some questions about a 2 cubic foot Centaur carbon filter I am setting up. It will be used to capture the iron precipitated out of the well water by a hydrogen peroxide injection. It has a 12x48 tank and a Clack WS1 valve that was previously on a water softener. Is the 12x48 tank large enough to hold 2cf of carbon and backwash properly? Doing research, some sites say that the backwash rate of the carbon should be 8-10gpm per square foot of media. I am assuming that with the roughly 7.8sq ft of this tank that if using the higher backflow rate of 10gpm then the clack valve would need an 7.5 gpm dlfc button, is this correct? Another concern is the type of underbedding needed. I have a old 16lb bag of #8 garnet here, is this okay to use under the carbon?

    The house that this filter is being used on has 3 bathrooms all with single head showers, no tubs, a washer, no dishwasher and there are two senior occupants. 99% of the time there are only two people living in the house, but up to 6 guests can use the house two or three times for up to a week at a time per year. I have only seen all three showers being run at once maybe a half a dozen times in the past 20 years. I figure a high water usage rate of around 9gpm with 3 showers going and can't really see all three showers and the washer running at the same time, but maybe the kitchen sink might get used for a glass of water or to wash dishes, but again it would be extremely rare to have all of these happening at the same time. Is 2 cu ft of Centaur carbon enough for 9gpm flow rate? Is one normal 14 minute backwash setting sufficient for this filter? How often should the backwash occur?

    Just FYI: The water supply has tested for 4ppm of ferrous iron, a PH of 7.3, TDS of 300, 9 grains of hardness, Manganese-Copper-Nitrites-Sulfides-Tannins-Iron Bacteria, nor Coliform were detected.

    I sure do appreciate any and all help you experts can offer. Most of the water treatment people where the house is located seem to be more interested in selling product that up to this date hasn't worked properly. I would much rather learn all I need to know from someone who knows what they are talking about and get the water iron free and then maintain the system then to rely on a few local water treatment shops.

    Gary has been pushing the Clack valve for years as a DIY's dream and it was Dittohead's video on the rebuilding of the Clack valve that sold me on this valve. His video on the Fleck 7000 rebuilding was awesome too, but I really liked the idea of there being no screws on the WS1.

    Thanks again for the help! John

  2. #2
    Water systems designer, R&D ditttohead's Avatar
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    A 12x48 is rated for 1.7 Cu. Ft. of media with a 50% freeboard (50% of the media height, not 50% of the tank). Assuming you fill the bottom dome (Domes are not considered in tank media quantities). Name:  dome.jpg
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    GAC is usually backwashed at 10 GPM per Sq. Ft. 6" x 6" x3.14 / 144 x 10 = 7.85 GPM, you should use a 7-8 GPM flow control on the Clack valve.

    Garnet is an excellent underbedding for GAC, just be sure it completely covers the bottom screen. Properly, it should fill the dome, but I doubt 16 pounds will do that. The Dome on a 12" tank is .13 Cu. ft. it will barely cover the bottom screen depending on what type of screen you have. #8 Garnet is approximately 150# per Cu. Ft.

    Backwash frequency depends on the water use, but considering the high level of iron, I would assume weekly or every other week should be sufficient.

    As to the Clack or 7000, both are excellent, and both should last 5-15 years between rebuilds. If you are using a water softener valve for the clack, be sure to plug the brine, and remove the brine piston from inside the valve. Not critical, but proper.

    How are you injecting your chemical?

    I am doing the 5800SXT rebuild next, I also am redoing the 7000 with some cut-away views.

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    DIY Junior Member JohnF10's Avatar
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    Thank you for your help! I will load the mineral tank with 1.7 Cu. Ft. of carbon and get some more garnet to fill the bottom dome. The bottom screen on the riser tube almost looks like a bunch of stacked plates with fine slots all around it and is approximately 3" or so tall. The brine piston removal was very easy using your excellent video as a guide and also using the clack manual to tighten up the drive cap assembly correctly. I am planning on using a Chemilizer pump to inject the peroxide. The house is on a shared well and will need a proportional rate pump and this looked like one of the best ways to get it without having to buy an electric injection pump, control module and flow meter. Hopefully it will work out as well as expected. Would you know what residual of peroxide that would be the best to shoot for before the water enters the carbon filter? It would seem to make sense to end up with as little H202 as possible after it oxidizes the rust, but I don't know if that is true.

    I look forward to your 5800 valve rebuild video and the cut-away views of the 7000 valve as well. I never knew that water treatment was so complex, but yet interesting at the same time.

    One last off the topic question. How much iron can a 1/3 cu. ft. of KDF-85 media remove by itself in a backwashing filter? I haven't had any luck finding that answer in my research on the stuff.

    Thanks again for your help! John

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by ditttohead View Post
    The Dome on a 12" tank is .13 Cu. ft.
    How is this calculated for a tank of a given diameter -- or is it not calculated, but given in a table I haven't found yet? I thought it would be half of a sphere, but doing that calculation for a 12" tank results in 0.26 cu ft. Doing the reverse calculation starting with 0.13 cu ft gives a diameter of 9.5", implying a tank wall thickness of 1.25 if the 0.13 cu ft volume is correct. Are the tank walls really that thick? Or am I assuming something wrong here? I'm trying ultimately to find the bottom dome volume of a 10" tank.

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    Water systems designer, R&D ditttohead's Avatar
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    Actually, the calculation is an estimate and changes by each tank manufacturer. It is not a true dome like half a ball, so the actual amount is usually charted, not calculated. I will add that chart to my next catalog, if I remember, I will post the most common dome capacities on Monday. The wall thickness also changes by each manufacturer and manufacturing technique. For the most part, they are all close enough so a chart will be accurate enough.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by ditttohead View Post
    ...I will post the most common dome capacities on Monday. The wall thickness also changes by each manufacturer and manufacturing technique. For the most part, they are all close enough so a chart will be accurate enough.
    Thanks. I've got a couple of empty tanks, one 10" and one 8" I could actually measure, but I doubt it'd be worth it.

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    DIY Junior Member statin's Avatar
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    Hello, I am curious how this project turned out. I actually am planning a similar project and surprised to find someone doing the same. If by any chance if the OP could either PM or post his results. Thanks, John

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    DIY Senior Member Bob999's Avatar
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    The Chemilizer pump is a positive displacement pump and NOT suitable for hydrogen peroxide.

    For hydrogen peroxide you need to use a peristolic pump such as the Stenner Pump.

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    That's all folks! Gary Slusser's Avatar
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    And rather than a 12" x 48" tank get a 12" x 52" tank.
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

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    DIY Junior Member JohnF10's Avatar
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    Quote Originally Posted by Gary Slusser View Post
    And rather than a 12" x 48" tank get a 12" x 52" tank.
    I will get a 12' x 52" tank if you think it is necessary. I just had the 12" x 48" tank on hand and thought it would do the job. Thanks for your help! John

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    Water systems designer, R&D ditttohead's Avatar
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    The 12x48 is fine. No need to get a 12x52. Even a 12x52 is only rated for 1.8 Cu. Ft., but most companies use it for 2 Cu. Ft. I would recommend household bleach injection. It requires a lower dosage than hydrogen peroxide, is readily available, and is highly stable in solution. Some people will say that the holding tank needs to be cleaned and the liquid solution changed regularly, in commercial applications this is true, for residential, just check the bottom of the tank for precipitates, clean as needed. Let the tank run almost dry prior to cleaning. Cleaning is nothing more than rinsing the tank out for a minute, not exactly difficult. The HN55 is one of my favorite designs, simple, accurate, inexpensive, and durable. It is a bit noisy so dont mount it to the wall behind your bedroom.

    As to the KDF85 question, it does a fairly good job as a non chemical iron filter, similar to pyrolox. Using this media for a whole house iron filter is an excellent idea, but should only be done after proper pilot testing, or by the dealers who are well versed in their regions water and the medias capability for that water. This is the same with most non chemical iron removal systems. When in doubt, chlorine injection, contact tank, GAC is always a safe way to go.
    Last edited by ditttohead; 12-08-2012 at 02:36 PM.

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    DIY Junior Member JohnF10's Avatar
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    "The HN55 is one of my favorite designs, simple, accurate, inexpensive, and durable. It is a bit noisy so dont mount it to the wall behind your bedroom." LOL! It might attract wood peckers with its clicking sound if mounted there! Thanks for the info on the KDF media, it sounds like an interesting media. Does it need the same 15% dissolved oxygen that birm, and filox need to work well? Thanks again for your help!

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    That's all folks! Gary Slusser's Avatar
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    Quote Originally Posted by JohnF10 View Post
    I will get a 12' x 52" tank if you think it is necessary. I just had the 12" x 48" tank on hand and thought it would do the job. Thanks for your help! John
    I forgot you already had the tank but, a 12 x 52 has an additional 4" and that means all 2.0 cuft and the underbed fits in the tank.

    BTW, I do not like peroxide or solution feeders but chlorine bleach is much better, less expensive and much easier to handle, find and store.

    Solution feeders can be a PIA to get to work consistently. The solution weakens in the tank and the solution will separate causing the stronger solution to be in the bottom of the solution tank where the pick up is. That is caused because bleach is heavier than water and will separate and fall to the bottom of the tank if not stirred constantly. Then each chlorine injection is weaker than the previous and maintaining the residual can be difficult. So you increase the volume of the solution and when you add more solution, you decrease the volume.

    I think a much better way to use chlorine is with an erosion dry pellet chlorinator and special mixing/retention tank that is equivalent to a regular 120 gal retention tank and allows draining sediment out the bottom followed by the carbon filter. I sold hundreds of them since the early 1990s and they work every time with little to no babysitting.

    http://www.apwinc.com/retention_tank.html
    Gary Slusser Retired (= out of business)
    Click Here to learn how to correctly size or program a water softener.
    CAUTION, as of Nov 12 2013 all YouTube videos showing how to rebuild a Clack valve have an error in them that can cause damage.

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    DIY Junior Member JohnF10's Avatar
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    Quote Originally Posted by Gary Slusser View Post

    BTW, I do not like peroxide or solution feeders but chlorine bleach is much better, less expensive and much easier to handle, find and store.

    Solution feeders can be a PIA to get to work consistently. The solution weakens in the tank and the solution will separate causing the stronger solution to be in the bottom of the solution tank where the pick up is. That is caused because bleach is heavier than water and will separate and fall to the bottom of the tank if not stirred constantly. Then each chlorine injection is weaker than the previous and maintaining the residual can be difficult. So you increase the volume of the solution and when you add more solution, you decrease the volume.

    I think a much better way to use chlorine is with an erosion dry pellet chlorinator and special mixing/retention tank that is equivalent to a regular 120 gal retention tank and allows draining sediment out the bottom followed by the carbon filter. I sold hundreds of them since the early 1990s and they work every time with little to no babysitting.

    http://www.apwinc.com/retention_tank.html
    I wonder if someone makes a small pump or mixer that could be used to recirculate the bleach or peroxide mixture in the solution tank that would help alleviate the stratification of the water/chemical mix? Time for more research! ;-) I like the idea of the pellet chlorinator, but since my Dad will be the one having to maintain the system most of the time I don't believe that he would like to have to use muratic acid to clean out parts of the feeder every couple of months. He has very bad arthritis in his hands and I think a bleach or peroxide system would be easier for him to keep up when I am not around. I appreciate all of the advice you have given me!

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    DIY Junior Member JohnF10's Avatar
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    Quote Originally Posted by Bob999 View Post
    The Chemilizer pump is a positive displacement pump and NOT suitable for hydrogen peroxide.

    For hydrogen peroxide you need to use a peristolic pump such as the Stenner Pump.
    Hi Bob, From what I have read about the chemilizer pump it can inject chlorine into the water. Here is one company that sells the HN55 just for this purpose. http://www.purewaterproducts.com/wat...edinjector.htm Is hydrogen peroxide injection different from chlorine injection?

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