Most of us don’t think about it too much when we turn on the hot water tap. We assume that the water is safe to use, or at least not harmful.

But a new study warns that hot tap water may actually pose serious health risks – and the culprit may be stagnant water sitting in your pipes and hot water tank.

What Are the Risks?

According to researchers, hot tap water can contain higher levels of lead, copper, and other contaminants than cold water.

This is because hot water can dissolve impurities in the pipes and tanks it’s stored in, which then wind up in your drinking water. The longer water is stagnant in your pipes, the more likely it is to pick up these contaminants – so if you don’t use hot water frequently, you could be putting yourself at risk.

In addition to these impurities, hot water can also contain bacteria that thrive at higher temperatures. Legionella, for example, is a type of bacteria that grows in stagnant hot water.

When people inhale water droplets contaminated with Legionella (such as in a shower or bath), they can develop Legionnaires’ disease – a potentially fatal type of pneumonia. Other types of bacteria, like Pseudomonas aeruginosa, can also thrive in hot water and cause infections in people with weakened immune systems.

Who is Most at Risk?

While anyone can be affected by contaminated hot water, certain groups are more vulnerable than others.

People with weakened immune systems – such as those receiving chemotherapy, organ transplant recipients, or people living with HIV – are at higher risk of developing infections from contaminated water. Infants, young children, and elderly people are also more susceptible to certain illnesses and should take extra precautions.

In addition, people who live in older homes or apartment buildings where pipes and tanks may be corroded or made of lead are at a higher risk of exposure to harmful contaminants.

How to Protect Yourself

Fortunately, there are steps you can take to reduce your risk of exposure to harmful hot water. These include:.

Flushing your hot water system regularly. Run hot water through all of your faucets and showers for several minutes each week to help prevent bacteria and contaminants from building up.
Setting your hot water heater to a lower temperature. The hotter the water, the more likely it is to dissolve minerals and impurities from pipes and tanks. Keep your hot water heater set to a temperature of 120 degrees Fahrenheit or lower (or as recommended by your manufacturer).
Using a water filter. A high-quality water filter (such as a reverse osmosis filter) can remove many contaminants from your drinking water, including lead and copper. Look for a filter that is certified by NSF International or another reputable organization.
Testing your water. If you’re concerned about the quality of your tap water, you can have it tested by a reputable laboratory. Your local health department or water utility can provide you with information about testing options in your area.
Replacing old pipes and tanks. If you live in an older home or apartment building with corroded or lead pipes and tanks, consider having them replaced with newer, safer materials.

The Bottom Line

While we may take our tap water for granted, it’s important to be aware of the risks that hot water can pose.

By taking the steps outlined above, you can help protect yourself and your family from harmful contaminants and bacteria – and continue enjoying safe, refreshing water from your tap.