Why is My Water Brown?

Red, Brown, Yellow – A Rusty Hue? You Might have Iron in Your Water.


Have you ever turned on your faucet expecting clear water and instead you see a mysterious red, yellow, or brown liquid? Have you ever noticed rust colored stains on your appliances or slimy red build up in your toilet? Reddish brown rust is an alarming color to see in your water, but don’t panic–it is most likely iron contamination. 

We’ve produced this handy guide to identify what type of iron contamination you might have and which types of treatments might help clear up your tap water.

How does iron get into the water supply?

Iron–the fourth most abundant mineral in the earth’s crust–is also present in groundwater; unless it is treated or filtered out, it enters the water supply. As pipes and well casings corrode and rust, they can release iron into the water as it flows through.

Will iron affect my health?

Iron is thankfully not dangerous to human health–it is in fact necessary for us to live and we consume iron in foods such as leafy green vegetables and red meat. The human body uses iron to carry oxygen in the blood, hence giving blood its rusty red color. While excessive consumption could lead to iron toxicity (the poison is in the dose, as they say), acute iron poisoning is not known to happen from tap water.

Detection & Treatment

We care about iron in water because it can cause unpleasant odors and tastes in drinking water or slimy residues and stains on our home appliances.

The form of iron that your water likely contains differs depending on whether your water comes from a (1) water utility or (2) private well

1. I use utility treated water and suspect iron contamination

Utility water (from a public water system) is filtered for iron, but treatment plants only reduce iron to levels below the legal concentration limit (0.3 mg/L)–they do not remove iron completely. Over time, small levels of iron can build up in the many miles of pipeline water must travel through before it reaches people’s homes. Disturbances to the pipes can then knock these mineral deposits loose and into the water stream, including:

  • Main pipeline breaks 
  • New construction 
  • Heavy irrigation or fire hydrant flushing 


The two most common forms of iron in public utility treated water are “ferrous” iron (“clear-water” iron) and “ferric” iron or  (“red-water” iron).

  • Clear-water iron: if your water comes out of the faucet clear but then turns red or brown after sitting
  • Red-water iron: if your water comes out of the faucet red or yellow


  • Clear-water iron: most commonly treated with a water softener. However, the filter must be changed or backwashed often, because iron will quickly plug it up.
  • Red-water iron: most commonly treated with a manganese greensand filter, but for small concentrations, a sediment filter, carbon filter, or water softener can be used.

You can also order a TapScore Essential Water Test or an Advanced City Water Test if you are unsure how to diagnose an iron contamination problem or purchase a treatment product, or if you want to know the concentration of iron in your water.

2. I use private well water and suspect iron contamination

Private well water is not usually filtered, so if there is iron in the source water or from your pipes, it will remain there until you filter it. 


Well water can contain clear-water iron or red-water iron, as public utility water can (see 1. above). It can also contain organic iron and tannins or iron bacteria, both of which are much much more difficult to remove.

  • Organic iron & tannins: iron reacts with naturally occurring tannins–organic matter from vegetation–to produce black residues. Iron can react with other naturally occurring organic acids to produce organic iron, which is usually yellow and brown.
  • Bacterial iron: iron bacteria are naturally occurring organisms that consume iron to survive, and produce a slimy red or brown biofilm in the process. They can enter a well during construction or repair.

If left untreated treated they can create an environment where more dangerous organisms can grow. Some common signs of iron bacteria include:

  • Tastes & odors: described as “swampy”, “oily or petroleum”, “cucumber”, “sewage”, “rotten vegetation”, or “musty”. The taste or odor may be more noticeable if the water hasn’t been used for a bit. 
  • Color: yellow, orange, red, or brown stains in sinks or toilets, on laundry, etc.
  • Red slimy deposits: sticky slime that is usually rust colored in toilets or pipes.

    It is best to test for iron bacteria because these symptoms could be signs of other bacteria as well.


    • Organics iron & tannins: can be treated with chemical oxidation followed by filtration. Water softeners, aeration systems, and iron filters may not work well because organic iron and tannins can “slow or prevent iron oxidation”.
    • Bacterial iron: iron bacteria are very difficult to remove, so physical removal, heat, and chemical treatment must be used. The most common treatment is “shock” chlorination, or adding a very strong chlorine solution to a well.

    If you are unsure of your iron source and it is staining your clothes or causing concerning smells, try our TapScore Essential Water Test or an Advanced Well Water Test with an iron reducing bacteria add-on.


    Iron contamination in water is not dangerous, but can cause undesirable odors, tastes, colors, stains, slimes, and in the case of iron bacteria, can create an environment for other harmful organisms to grow. Because there are so many different kinds of iron in water, you must identify which form you are dealing with to determine which type of removal treatment will work. If you own a private well, we recommend that you test your water every three years to be sure it remains clean.

    If you have any questions, be sure to email us at hello@simplewater.us!