Health

How to Tell if Your Tap Water Is Toxic

T Beverly March 22, 2026 No Comments

Tap water is usually clear and neutral in taste. Learn which changes in color, smell, or flavor may warrant a professional check.

Written by Ayisha Sharma

Medically Reviewed by Melinda Ratini, MS, DO 

Tap water can sometimes taste, smell, or look different from the usual tasteless and transparent liquid that you are used to drinking. Not all changes in the taste, smell, and appearance of tap water indicate a health risk, but some changes are more concerning than others. In these cases, you may need to stop drinking the tap water and get it checked by a professional.

Normal tap water is tasteless and odorless. If your water is contaminated, it may have a strong smell or taste of the following chemicals:

  • Chlorine
  • Petroleum or gasoline
  • Turpentine
  • Metals (iron, copper)

Tap water that smells or tastes of chlorine is not usually a cause for concern. Tap water is disinfected with chlorine to make it clean and safe to drink, so the smell is likely left from the treatment process. If the smell or taste of chlorine is very strong, however, it’s best to contact your local health agency.

Tap water that smells or tastes like petroleum, gasoline, or turpentine is rare and could pose a serious health risk. If your water smells like these chemicals, the water supply may be contaminated by an underground storage tank that’s leaking byproducts of gasoline, paint, detergent, or ink. Stop drinking the water and contact your local health agency immediately.

Tap water that smells or tastes like iron or copper could contain traces of the metals from which your water pipes are made. While water that contains iron is not a cause for concern, consuming too much copper through your water could lead to copper toxicity, which can cause bad headaches, nausea, diarrhea, and jaundice (a condition marked by yellowing skin).

It’s best to get metallic tap water analyzed by a certified lab.  Contact your local health agency for a referral.

If your tap water tastes or smells unpleasant but not chemical, it could still be contaminated. Tastes and smells that suggest water contamination include:

  • Rotten eggs
  • Moldy earth
  • Fish
  • Salt

Tap water that tastes or smells like rotten eggs or sulfur likely contains hydrogen sulfide. Hydrogen sulfide is released when a certain kind of bacteria is present in the water or somewhere in your water system. Drains, water heaters, wells, and the inside of pipes can harbor bacteria.

Usually, your water heater is the culprit when water smells of rotten eggs. The heater contains an element that protects it against corrosion, but this element can give off a rotten egg smell as it breaks down over time. Contact a plumber to check if this is the case. If you’ve ruled out the drain and heater as the cause of the rotten egg smell, stop drinking the water and contact your local health agency.

If your tap water smells like moldy earth or fish, there’s likely solid organic matter in your water system or source and it is beginning to decay. Pour a small amount of water into a narrow glass and swirl it around before smelling it. If the water loses its smell upon swirling, the decaying matter is probably located in the sink drain. If the smell is still present after swirling, the decaying matter is probably located in the water source itself.

Tap water contaminated with organic matter is ultimately harmless. Water that tastes too salty is also not usually a cause for concern.  A salty taste in your water may simply indicate naturally high levels of sodium, magnesium, or potassium in the water in your area.

If you live near the seaside, however, salty water could indicate that seawater is seeping into your tap water supply. Contact your local health agency to make sure this is not the case.

Normal tap water is transparent and colorless. If your water suddenly turns a different color, something may have disturbed the flow in the main water line.

Contaminated tap water may turn the following colors:

  • Green or blue
  • Black or dark brown
  • Red, orange, or yellow
  • Milky white or cloudy

Tap water can turn green or blue due to the erosion of copper plumbing. This is probably the case if the green or blue color is accompanied by a metallic smell and taste. As mentioned earlier, consuming too much copper in drinking water may lead to copper toxicity. If your tap water looks blue or green, be on the safe side and contact your local health agency.

Black or dark brown tap water is usually caused by manganese in your water or water pipes. Flush all your cold-water faucets and toilets, and wait an hour before checking if the water has cleared up in color. If it’s still black or dark brown, contact your local health agency.

If your water pipes are made of galvanized iron, steel, or cast iron, the rust in your pipes may turn your water red, orange, or yellow in color. The water may have a metallic taste and be unpleasant to drink, but iron in drinking water is not a health risk.

If your tap water appears milky white or cloudy, fill up a glass and wait for a couple of minutes. If the water at the bottom of the glass starts to clear up first, the cloudiness was caused by trapped air bubbles, and the water is not a cause for concern.

Leave a Reply