Can a water softener be used to remove iron from water? The answer is yes - but it's complicated! And because it's complicated, there's a lot of misinformation that exists in the marketplace - both online and with conventional water treatment dealers.
So what's the deal with iron? How do I know if a softener will remove the iron in my water? The key to understanding how well a water softener will remove iron is to understand some key bits of info about your water chemistry: iron, total hardness, and pH.
pH - Ignore At Your Peril
If there's a hidden secret to knowing how well a water softener will remove iron, it's pH. But to understand the important role pH plays, we first need to understand a little about the chemistry of ions.
An ion is a charged particle. It can have a positive or a negative charge. If it has a charge, it's an ion. When substances dissolve in water they are either ionic or non-ionic dissolved substances. Sugar, as an example, dissolves in water as non-ionic substance (it has no charge). Common table salt, however (Sodium Chloride) dissolves as an ionic substance - the sodium and chloride break apart with each particle carrying a charge. The sodium carries a positive charge and the chloride carries a negative charge.
Some substances that are placed into the water will dissolve into their ions no matter what the water conditions are. But some substances are sensitive to other water conditions, and may or may not dissolve as ions depending on the conditions. The most important of these factors is pH.
The pH of the water will affect whether or not some substances dissolve into ions. Usually, an acidic pH (below 7) will encourage substances to dissolve as ions and a basic pH (above 7) will prevent substances from dissolving as ions. This is important as it relates to water softeners because they are ion-exchange technologies. Water softeners will only work on ions.
So the key to knowing how well a softener will remove iron is all about understanding the pH. If the pH is acidic the iron will exist in the water in its ionic form, and the softener can easily remove it. However, if the pH is basic, the iron will likely exist in the non-ionic form and a softener won't be able to remove it.
Clear Water Iron vs. Precipitated Iron
The good news about the two main types of iron that can exist, is that they impart a different colour to your water. So identifying what you've got is straightforward. The ionic (dissolved) form of iron doesn't create any colour in your water. For this reason, it's typically called "Clear Water Iron". The non-ionic form does impart a colour to the water. The colouration can range from yellow to orange to brown. This may also be know as precipitated iron.
Here's how to test your water to figure out what type of iron you've got:
find a high-flow faucet (bathtub faucet often works best)
turn the faucet to full-flow cold only
let this run for a full five minutes to clear all standing water out of the plumbing
fill a large white bucket with at least 12 inches of water
put the bucket in a well lit area
if you immediately see any yellow/orange/brown colouration in the water, you've got precipitated iron that a softener will not remove
if the water is clear, then you've got clear water iron
It's important to note, that clear water iron that is left exposed to air will eventually change to precipitated iron.
If it turns out that you have precipitated iron, all is not lost! There are technologies, like the Aquatell AIO Iron Filter that will do a great job for you.