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Home Repair - - If it ain't broken, don't fix it. Otherwise look here.
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Posted by RCW on October 4, 2006, 11:22 am
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.
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Posted by John Gilmer on October 4, 2006, 12:56 pm
> 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.
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