Is Re-Boiling Water Safe?

Tea kettle on a gas stove

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Consuming re-boiled, clean, uncontaminated drinking water will not cause cancer or poison you or your family. As long as your water comes from a source that is regularly inspected, you can boil it as many times as you want.

When Re-Boiling Water Can Be Unsafe

The idea behind this myth is that boiling water concentrates any solid substances that are in the water. Maybe you've seen white chalky stuff stuck to the sides of your pot or tea kettle after you've boiled water. It's just calcium, which is harmless. As long as there's nothing bad in your water to concentrate, there's no health concern.

So what if there is something nasty lurking in your water? 

If your water contains arsenic, lead or nitrates, then boiling it will increase the concentration of those substances. At what point does it become dangerous? That's hard to tell, but that's why water needs to be regularly inspected. 

The levels of both nitrates and arsenic are regulated, and water supplies must be monitored in towns and cities, so if your tap water comes from a city water source, it's safe. 

These toxic substances can get into your water in a variety of ways. Groundwater may contain nitrates, which are chemicals often found in fertilizer, and arsenic that may occur naturally or from a farm or industrial waste. If you live in a rural area and have a well, the water must be tested. 

Lead doesn't come from the water source itself. The contamination happens at home. Lead can contaminate a water supply through old plumbing that's held together with lead solder or stored in tanks lined with lead. Exposure to lead can cause emotional and behavioral problems. Lead can't be used for plumbing anymore, but it might be present in buildings and houses built before 1986.

3 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Arsenic and Drinking Water from Private Wells.

  2. United States Environmental Protection Agency. Chemical Contaminant Rules.

  3. MedlinePlus. Lead Poisoning.

By Shereen Lehman, MS
Shereen Lehman, MS, is a former writer for Verywell Fit and Reuters Health. She's a healthcare journalist who writes about healthy eating and offers evidence-based advice for regular people.