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How to Get Rid of Rust in Well Water

This Old House plumbing expert Richard Trethewey has some solutions for a homeowner experiencing iron and rust in their well water.

rusty water pouring out of a faucet iStock

Our well water has iron in it, which affects its taste and causes staining. A local water-treatment company says that a standard water softener can remove the iron, but I don’t want to drink softened water or have its salty backwash pumped into my yard. Can you suggest another way to get rid of the iron?

Patricia McMartin, Winchester, VA

A:

Several options are available for removing iron, but the treatment varies depending on the kind of iron you have, along with other factors. If you haven’t already done so, get a water test to determine the type and amount of iron, in parts per million (ppm), as well as the water’s pH and dissolved oxygen content.

The three most common types of iron in well water are:

  1. Iron bacteria, which show up as reddish slime in toilet tanks
  2. Ferric iron, also known as red iron, which turns water a cloudy orange
  3. Ferrous iron, also known as clear-water iron. Ferrous iron doesn’t affect water clarity, but it stains ceramics and clothing and has a rusty taste. Dollars to doughnuts, that’s the type you have.

I know you’re against using a water softener, but it can be an effective and economical way to remove low iron levels—3 ppm or less—if the water’s pH isn’t too high. A softener can remove iron under less-than-ideal conditions, but then its resin beads may fail and need to be replaced, as often as every two to three years.

When a softener doesn’t work, there are many specialized iron filters that will. They all operate on the same principle: to oxidize the dissolved ferrous iron and convert it into ferric-iron particles that can then be captured by running the water through a bed of minerals.

Some filters inject oxidizers such as air, chlorine, hydrogen peroxide, or ozone into the water ahead of the mineral bed. Others use manganese-rich media such as Greensand Plus or Birm to oxidize and capture the iron in one step. And some combine injection with oxidizing media. To remain effective, some manganese-based filters have to be recharged periodically with another potent oxidizer, potassium permanganate.

All these filters work best with water in the 6.5 to 8 pH range. And they all have to be flushed—backwashed—regularly to remove the buildup of iron particles. The process uses a lot of water, about 10 gallons per minute per square foot of mineral media. If the system is calibrated properly, the iron-rich backwash is safe for municipal sewers and septic systems.

When comparing iron filters, make sure you know how many gallons of backwash they’re likely to use, the required flow rate during a backwash, and the cost of any chemicals that have to be added.

Shown: In well water, red iron makes itself obvious. Clearwater iron is invisible, yet still affects taste and stains sinks and clothing.