Is warm tap water safe for drinking or baby formula?

The EPA gives a direct answer to the hot-water question: "Hot water dissolves lead more quickly than cold water and is therefore more likely to contain greater amounts of lead. Never use water from the hot water tap for drinking, cooking, or making baby formula." Its home-action page repeats the rule: "Use only cold water for drinking, cooking and making baby formula. Remember that boiling water does not remove lead."

The EPA's reason is about lead that can dissolve from plumbing, not about the summer heat itself. A tap labeled cold that runs warm because of a hot attic or shallow pipes is not the hot water tap. But warm water is warmer water, and the habit that keeps you safe is easy: let the tap run until the water feels properly cold before you use it for food or drink. The EPA also advises flushing. It says "before drinking or cooking, flush your home's pipes by running the tap, taking a shower, doing laundry or running the dishwasher." You can catch the first flush in a pitcher for plants.

Do not fix a warm tap by boiling. The EPA says boiling does not remove lead, and the City of Phoenix says the same: "Use cold water. Boiling water does not remove lead from water."

### What about lead in Phoenix?

The City of Phoenix says: "Since starting field investigations in 2021, we have not found any lead lines." That statement is about the city's service lines, the pipes from the main to your home. It does not describe your home's interior plumbing, fixtures or solder, which vary with the age of the house and what has been replaced. The EPA notes that the lead service line "is the pipe that runs from the water main to the home's internal plumbing," and that such lines "can be a major source of lead contamination in water." Phoenix also lists filters as a step: "Use water filters certified to remove lead." If you want to know what is in your own water, how to test home water for lead explains the options, and is Phoenix tap water safe to drink covers the city's water quality reports. For what else can be in local water, see contaminants in Arizona tap water.

The AAP says it is "important to use clean water from a safe source free of bacteria or other microbes (germs) that may cause disease." On tap water it says: "Unless there is a known contamination of your local water source, you can use tap water to prepare concentrated liquid or powdered formula." Combine that with the EPA advice: the tap water is the source, and cold is the water to draw.

For some babies the AAP asks for more care: "For infants younger than 2 months of age, those who were born prematurely and those who have a weakened immune system, boiled water should be used to kill any microbes. After boiling the water, let it cool for about 5 minutes." Boiling is for germs. It does not remove lead, so it does not replace drawing cold water in the first place. If you are boiling, start with fresh cold tap water.

Two more AAP rules matter here. Follow the formula's directions exactly, because "formula that is diluted with too much water, for example, can cause serious health and development problems for your baby." And test the temperature before feeding: "Test warmed water in advance to make sure it is not too hot for your baby. The easiest way to test the temperature is to shake a few drops on the inside of your wrist."

Here the danger is heat, not lead. The AAP says "water temperature can fluctuate as it moves through your home's pipes, and even small changes can cause scalds." Its recommendation: "The AAP recommends that the hottest temperature at the faucet should be no more than 120 degrees Fahrenheit to help avoid burns. In many cases you can adjust your water heater setting to not go above this temperature." And it says "hot water scalds are the top cause of burns among babies and young children."

In a Phoenix summer this matters twice. If your cold line runs warm, a mixing valve or single-handle faucet delivers a hotter blend than the handle position suggests. The AAP's bath rules are simple:

• Fill the basin with about 2 inches of water that feels warm, not hot, on the inside of your wrist or elbow.
• If you bathe your baby in a sink, turn off the faucet before placing the baby in the water.
• "Never bathe your baby in running water," and do not use a sprayer attached to the faucet.
• Never leave a baby alone in the bath, even for an instant.

To check your water heater setting, see what temperature to set a water heater to. If you cannot see or reach the setting, a plumber can check it.

Summer heat in attics, exterior walls and shallow pipes can warm water that sits still. That explanation, and the tests to run, are in why cold tap water is hot in a Phoenix summer. If your cold water stays warm after a repipe, see why cold water is not cold after an Arizona repipe. Running the tap for a minute before you fill a pitcher, then keeping the pitcher in the refrigerator, gives you cold water on demand.

• It is not a water test. Nothing here tells you what is in your water. If you have a private well, an older home, or any doubt, test the water.
• It is not medical advice. Questions about a specific baby, pregnancy, or blood lead levels belong with a pediatrician or your doctor.
• Color, smell and taste are separate questions. If the water is brown, cloudy or smells, see why tap water is brown or smelly hot water causes and safety.
• A warm tap that never cools is a plumbing problem. Have it looked at.

HQ Plumbing & Air is licensed and insured, gives free estimates, and quotes the price up front. If the water heater setting is out of reach or a cold line runs hot all day, we can take a look. We are available 24/7 for emergencies.