Filter for iron in water

Discussion in 'Home Repair' started by RCW, Oct 4, 2006.

  1. RCW

    RCW Guest

    Here in NH, lots of people with wells have iron in their water. The
    question often arises as to how to filter this stuff out.

    Actually, iron (the red, visible kind) is easy to filter. Because of
    electrostatic attraction, this type of iron wants to attach to
    something - anything. You could run rusty water down a 2" pipe (long
    pipe, very very long) and it would come out clean at the other end.

    So, with this in mind, avoid using filters with a small micron rating.
    Larger is much better to avoid premature clogging.

    In my house, I use a 1.5 cu.ft. automatic backwashing filter filled
    with a medium called "Filter Ag". It has a 20 micron size rating and
    it works slick. The water is sparkling clean.

    Now here's the rub. Water from my well has TWO kinds of iron in it.
    The first kind is ordinary rust which, as I mentioned, is easy to
    filter out. The second kind, is disolved iron which is clear. This
    cannot be filtered out. So what to do?

    This disolved iron must be oxidized so that it becomes ordinary rust
    which can be filtered out. There are several ways to do this: (1)
    Bubble air through the water. Municipal water systems sometimes do
    this. Tough for a homeowner though. (2) Add a tiny amount of Chlorox
    bleach. The bleach gives up oxygen molecules to oxidize the disolved
    iron and the left-over bleach molecule (minus the oxygen) becomes an
    ordinary table salt molecule. Since we're talking tiny amounts here,
    the salt left in the water is trivial - almost unmeasurable.

    This is the method I chose and it works. A special chemical injection
    pump is used for the bleach, plus you need a large (I use 120 gal)
    retention tank to allow adequate reaction time. This tank is in
    addition to the regular bladder water tank you need for a well system.
    All of this is followed by the filter.

    (3) You can buy a filter that uses greensand for the medium. This
    avoids having to use a chemical pump and retention tank but, you have
    to periodically recharge the greensand with potassium permanganate.
    Not for me thanks.

    I hope this info helps someone.
    RCW, Oct 4, 2006
    #1
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  2. RCW

    John Gilmer Guest


    > This disolved iron must be oxidized so that it becomes ordinary rust
    > which can be filtered out. There are several ways to do this: (1)
    > Bubble air through the water. Municipal water systems sometimes do
    > this. Tough for a homeowner though.


    Well, my pressure tank is "Air over Water." Each time the deep well pump
    starts it forces a slug of air into my tank. (A "air volume control valve"
    on the side of the tank bleeds out excess air.) I find myself wondering if
    that amount of air would be sufficient to oxidize the Fe.

    In any case I don't see any real problem to "bubble air" through an
    air/water tank. If you had a sealed air pump it would take little energy
    to pump air from above the water and inject it into the supply pipe from the
    well. The "head" would be about 5' of water or about 3 psi.
    Alternatively, the intake from the well rather than just filling from the
    bottom could, say, spray water on the top of the tank. The air volume
    control valve would have to be shielded to keep it from spitting out water
    when it operates.

    "Around here" many of the schools are still on well water. The standard
    installation has two tanks. One tank received the water from the deep well
    pump. It is air/water with the air being at atmospheric pressure. Since
    it isn't under any real pressure it's cheap to put in a tank that holds well
    over 1000 gallons. The second tank is the pressure tank on the order of
    300 gallons. If homes had such an arrangement it would make it a lot
    easier to treat various water problems. Chemicals or air can be injected
    into the main holding tank at low pressure and the deep well pump would be
    sized to the peak average consumption rather than the maximum consumption.
    John Gilmer, Oct 4, 2006
    #2
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