Blue/Green Stains On Bathroom Fixtures? A GA Plumber Explains


If you’ve noticed bluish-greenish stains in your bathroom and other water appliances, you’re probably wondering if it’s a sign of a more serious problem.

Well, it depends on what’s causing the stains in the first place.

Blue or green stains in your sink/bathtub/toilet can be caused by:

  • Mold
  • Corrosive water
  • Electrolysis

Not sure which is your issue? We’re here to help.

We’ll show you how you can determine what’s causing your stains and what you should do to prevent them in the future.

Cause #1: Mold or mildew

There are thousands of different kinds of mold. But one in particular, Penicillium, has a blueish-greenish hue.

Penicillium on bathtub faucet. Source

How to tell if it’s mold:

  • Its texture is fluffy, velvety or hairy
  • Darker, discolored patches of mold near it (often different mold groups grow together)
  • There’s damage to the surface. Mold can cause curling or peeling of vinyl, paint or other materials it grows on

How to clean and prevent it:

Mold growth is best removed by using an EPA-registered mold and mildew disinfectant.

But unfortunately, your bathroom will always be very prone to mold growth because of the amount of moisture readily available.

According to the EPA, the best way to get rid of indoor mold is to control moisture and leaks. Some ways you can do this include:

  • Squeegee water off shower walls after showering
  • Run the fan or air conditioner after showering/bathing
  • If you have tile, seal any grout lines to prevent trapping moisture in tight, dark spaces

Cause #2: Corrosive water

Corrosive water is “aggressive” water that eats away at the materials it comes into contact with. So, if your bathroom piping is made of copper, lead or other metals, the bluish stains in your bathroom could just be the insides of your corroded pipes.

How to tell if your water is corrosive:

Corrosive water can be determined by its pH levels, calcium concentration, hardness, etc. So, the only way to know for sure if your water is corrosive is to have your water tested.

But other signs of corrosive water include:

  • Metallic-tasting water
  • Bathroom piping that has (or is prone to) small leaks

Note: Corrosive water is usually not dangerous to consume but it is a nuisance many homeowners prefer to avoid.

How to clean and prevent it:

Cleaning the bluish-greenish stains caused by corroding pipes is easy. Just mix vinegar and baking soda into a paste, apply to the stains and wait about 10 minutes before wiping off.

To prevent these stains, you’ll want to have your water tested to see what is making your water so corrosive. Depending on your particular problem (low pH levels, level of salt in water, etc.) you can most likely find a whole-home water filtering system that can correct it.

Cause #3: Electrolysis

If your plumbing is composed of different types of metals, the blue or green stains might be caused by electrolysis. Electrolysis happens when two different kinds of metals touch in the presence of water. The “least noble” metal (the one that is more reactive) will start corroding.

For example, if a stainless steel pipe touches a copper pipe, the copper pipe will start corroding because copper is less noble than stainless steel. And corroding piping leads to bluish, greenish stains in your bathroom appliances.

Corrosion occurred here where copper piping attaches to galvanized steel. Source

How to tell if it’s electrolysis:

The best way to tell if electrolysis is causing the blue-green stains in your bathroom is to have a plumber take a look at your piping and determine if dissimilar metals are being used.

How to clean and prevent it:

You can use the same baking soda and vinegar paste to remove stains caused by electrolysis.

To prevent it from happening again, you’ll want to have a plumber find the source of the issue and replace the piping with a nonmetal.

Not sure what’s causing those blue-green stains? Ask an Atlanta plumber

If you can’t get rid of those annoying stains in your bathroom, we’re here to help. Mr. Plumber provides expert plumbing service to Atlanta, Marietta, Roswell, Alpharetta, Johns Creek, Newnan, Lawrenceville, Jonesboro and the entire Atlanta metro area.

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