It’s very common for well owners to experience iron contamination. If it’s happened to you, you’ll know that high levels of iron cause a variety of plumbing issues, from discolored water to stubborn orange stains.
When iron is not properly removed from the water supply, it can encourage the growth of bacteria that clog up pipes and make water stagnate.
Unfortunately, many people use incorrect methods to remove iron from well water. The most popular filtration devices contain activated carbon cartridges, which are great for many common contaminants, but are mostly ineffective when it comes to iron.
This is due to the fact that most iron must be oxidized before it can be filtered. Oxidation is basically the scientific term for exposing iron to the air, which makes it less soluble and easier to filter from the water supply.
Here’s how to correctly choose a well water filter for iron, and the different types of iron to look out for.
Why is there iron in my well water, and is it dangerous?
The good news is that iron contamination is not considered a health risk by itself. Well water contaminated with iron is generally safe to drink, even if it doesn’t look or smell particularly appetizing.
However, other contaminants may be present alongside iron that do require treatment before the water is considered safe for consumption. So always ensure that your water supply has been tested for bacteria, viruses, and heavy metals like lead.
Iron is a naturally occurring earth metal that exists in bedrock throughout the US. Because well water spends long periods of time traveling through the earth before it reaches a domestic well, it has the opportunity to absorb large amounts of metal and minerals such as iron.
Alongside iron, it’s not uncommon to find calcium, magnesium, arsenic, sulfur and other elements in well water.
Why does iron need to be oxidized before it can be filtered?
Iron can exist in well water in two main forms: dissolved and undissolved.
More commonly known as rust or red-water iron, undissolved iron is an insoluble matter that’s carried along in the water supply. These small particles of iron contamination may be microscopic or visible to the naked eye and can cause water discoloration as well as metallic tastes and odors (think the smell of pennies).
Undissolved iron is already oxidized, which is the chemical reason behind why it’s insoluble. In this form, iron can be easily screened from well water using any kind of sediment or micron filter.
It’s when iron exists in a dissolved, unoxidized form, that it becomes much trickier to remove.
Also known as clear-water iron, dissolved iron can pass straight through sediment filters, micron filters, and most types of basic home water filter systems. This type of iron is not visible in its dissolved forms, but when it comes into contact with sinks, bathtubs, shower trays, and other surfaces, it can produce brightly-colored stains that are difficult to remove.
Dissolved iron also makes water more hospitable for iron bacteria—a class of microorganisms that thrive in iron-rich water. Like iron itself, iron bacteria don’t pose a health threat to humans, but they can clog plumbing systems and coat the tops of wells in a thick film.
How to oxidize iron and remove it from well water
The correct way to remove iron from well water is to use a filter with two stages: an oxidizing stage followed by a granulated media or micron screen.
If a well has a serious iron contamination issue then a third chlorination stage may also need to be added to protect against the growth of iron bacteria in other parts of a home’s plumbing system.
There are two popular types of filtration systems that contain oxidizing and screening stages. These are injection filters and KDF filters.
Injection iron filters
Injection filters have large tanks that need to be installed in a basement or outside of the home.
They work by injecting an oxidizing substance into the water supply to initiate the process of converting soluble iron. The most common types of substances for an injection filter to use are air or chlorine.
Air injection filters simply add a pocket or air (which contains oxygen) to convert soluble iron.
The benefit of using air is that the homeowner doesn’t need to refill anything. However, air injection filters do raise the risk of iron bacteria growth if the filter system isn’t sufficiently powerful for the amount of iron in the well water.
Chlorine injection filters use a feed pump to periodically inject chlorine into well water, which has an oxidizing effect.
While homeowners do need to monitor the chlorine pump and refill it when it runs out of disinfectant, the benefit of chlorine injection systems is that they inhibit the growth of iron bacteria through plumbing.
Both types of injection filters use similar methods to remove iron from well water once it’s been oxidized. Usually, this consists of granulated green-sand filter media.
KDF cartridge filters
KDF filters are far more recognizable to homeowners. They are usually small enough to be installed under sinks and are constructed with a plastic casing.
KDF filters use replaceable cartridges that contain a granulated metal alloy. This is usually made from copper and zinc, and are generally cheaper filters for removing iron.
When iron-contaminated water passes through this mix of metals, a chemical reaction between the soluble iron and the KDF media converts the iron into an insoluble state.
Secondary filter cartridges containing carbon or green-sand media then screen out the undissolved iron content.
The bottom line
- Removing iron from well water isn’t hard, but it does require a different kind of water filter from the type usually found in homes
- Iron must be oxidized before it can be completely removed from well water. If it’s not oxidized, only insoluble iron can be removed.
- Insoluble iron is particulate matter that is carried in the water supply and affects water appearance and taste. Soluble iron is dissolved into the water supply, causing staining and bacterial growth.
- An oxidizing system converts soluble iron into insoluble iron, so the entire iron content of well water can be screened from the water supply.
- The two most popular types of well water filters for iron are KDF cartridge filters and chlorine injection filter systems.