Iron in Groundwater: A Primer for Drillers
In recent columns, I have discussed the matter of hard water as found in groundwater. Looking at a water map of the U.S. recently, I noticed that most of the Great Lakes states — which include Michigan, Ohio, Indiana, Illinois, Wisconsin and Minnesota, plus the non-Great Lakes state of Iowa — all have groundwater that is classified as very hard. I also noticed that some areas, especially New England, do not have a hardness problem, or at least they have less of a problem than we do here in the Great Lakes area. I am aware that other regions of the country have problems with corrosive water, methane gas and hydrogen sulfide, but all my experiences are in Michigan. So, this column will deal with the groundwaters of my area.
A typical well in southern Michigan will produce water that is about 20 to 25 grains hard and has somewhere around 3 parts per million (ppm) of iron. It has always been interesting to me that we quote hardness in grains per gallon and iron in ppm or mg/liter. (There is a conversion number, but off the top of my head, I can’t recall the method to express measures of hardness and iron in equivalent amounts.) When it comes to domestic use, while hard water is to most people not pleasing, it can be dealt with. Add enough soap or soap powder, and it can produce a clean wash to a person’s body or from a washing machine. Hard water doesn’t help the inside of pipes or water heaters, but it is something one can get used to. I have some relatives that grew up on hard municipal water who absolutely hate soft water. They claim it’s slimy. When these persons visit and stay overnight, I tell them I will set my water softener to make the water extra soft and even slimier. They reply, “Thanks a lot, John.” Of course, you can’t really do this. A softener will take the hardness level to 0, and that is it.
A water softener will change water from hard to soft, and is a relatively simple machine. It does not need much maintenance — just a good supply of the salt it uses to regenerate, as I have written about in recent columns. I also noticed from this water map that northern Michigan has water that is less hard and, I believe, quite a bit less hard than southern Michigan. Iron, on the other hand, is a tougher problem. As I said earlier, virtually every well I ever drilled has water with high iron content. What do I mean by high iron? Well, I believe that an iron content over 0.2 ppm will cause staining. You can see this on buildings and walkways that have been watered with overspray from lawn sprinklers. It doesn’t take very long for a rather ugly looking reddish-brown stain to occur on any surface. This includes concrete, brick and all types of siding. I understand the EPA recommends that water for human consumption have no more than 0.3 ppm. Iron is not listed as a contaminant, and I have never heard of a person or animal getting sick from drinking high iron water, but water with high concentrations is certainly a problem for the modern household. I was speaking recently about iron in water with a good hydrogeologist who has been a friend for many years. He said he once encountered water in another state that tested at 22 ppm iron. Yes, you read it right: 22 ppm. This was from a test well for a food processing plant and, needless to say, they never drilled the production well.
Having given you all this background, it is my experience that iron in groundwater is much harder to contend with and eliminate than hardness is. Iron in groundwater occurs in two forms. One is called ferric iron, which is actually small particles of iron that can be seen. It is what we would call rust and, indeed, is the cause of rusty water. The other form of iron is ferrous. It is in solutions and can’t be seen even with a microscope. Ferric iron can rather easily be filtered; ferrous is another story.
In days gone by, our industry used what might be called a standard hydro-pneumatic tank. This was a vessel or tank — usually made of steel, but sometimes other material — that contained water and compressed air. If you have read my columns for any time or have been in the business for any time, you know what I am talking about. These tanks tend to produce water with ferric iron in it — again, rusty water. The iron was not from the tank or the well casing as some believed, but from the water itself.
Rusty water can be treated using a filter. There are several types of filters that work very well for this purpose. The simplest is a cartridge type filter that is sold by water conditioning professionals, or can be purchased at a hardware store or big box home center. The filter elements of these units come in assorted coarseness levels and are, in effect, strainers. When the filter becomes plugged or the surface is coated with trapped iron, the cartridge must be replaced. While some say otherwise, I have never known an effective method to clean a plugged filter element.
Replacement of the cartridge is rather simple and a bit expensive, and has the downside of requiring attention from the homeowner. In a busy, busy 2019, many, if not most, homeowners don’t have the time to service water conditioning equipment. When a filter element becomes plugged, flow rates are badly reduced and, in the water happy home of 2019, this is a problem. I have seen hookups that used two cartridge filters and, years ago, I sold a unit that had, I believe, six cartridges in a common tank. Each cartridge in that unit was placed on a sleeve with a large nut to hold it on, and the sleeve itself was inserted into a tapered hole in a manifold in the main unit. This unit had a much higher flow capacity than a single cartridge type did, but was a little difficult to service. I was never really satisfied with this unit, although it worked well for my customer.
Next time, I’ll write about some other effective iron filters for rusty water and later move on to the difficulty of water with ferrous iron. As I write this in mid-January, we have very little snow on the ground. I can still see a lot of green grass on my property, although we did have a light snow today. A big, bad storm is predicted for this weekend for almost the entire country. We have had big bad storms here before and lived through them. We will likely live through this one. Until next time, thanks for reading this and continue to enjoy life along with your hard work.
For more John Schmitt columns, visit www.nationaldriller.com/schmitt