Can I drink or cook with hot tap water? What are the potential issues with using hot water at home from the boiler?
Many people wonder if it is safe to drink or cook with hot tap water, especially when they need hot water quickly and do not want to wait for the kettle or the stove. However, using hot tap water for drinking or cooking may not be a good idea, as it can pose some health risks and affect the taste and quality of your food. In this article, we will explain where the hot tap water comes from, why it can be unsafe to drink, what contaminants it may contain, and why you should not cook with it.
Where does the hot tap water come from?
Hot tap water is not the same as cold tap water that has been heated up. Hot tap water comes from a separate source, usually a water heater or a boiler, that stores and heats up water for domestic use. Depending on the type and age of the water heater or boiler, the water may be heated by electricity, gas, oil, or solar power. The water heater or boiler may also have a tank or be tankless, meaning that it heats up water on demand.
In some larger buildings or cities, the hot tap water may come from a central heating system that distributes hot water to multiple units or buildings. This system may use a large boiler, a heat pump, a geothermal source, or a cogeneration plant to heat up the water. The water may then be stored in a large tank or circulated through a network of pipes.
Why is the tap water from the water heater or boiler unsafe to drink?
The tap water from the water heater or boiler can be unsafe to drink for several reasons. First, the water may not be treated or filtered as well as the cold tap water, which means that it may contain more bacteria, viruses, parasites, or other microorganisms that can cause illness. Second, the water may be exposed to higher temperatures and pressures, which can leach out metals, chemicals, or minerals from the pipes, fittings, or the water heater or boiler itself. These contaminants can accumulate in the water over time and affect its taste, smell, color, and safety. Third, the water may stagnate in the tank or the pipes, especially if the water heater or boiler is not used frequently or is set at a low temperature. This can create a favorable environment for the growth of harmful bacteria, such as Legionella, which can cause a serious lung infection called Legionnaires' disease.
The tap water from the central heating system can also be unsafe to drink for similar reasons. Additionally, the water may be mixed with additives, such as corrosion inhibitors, antifreeze agents, or biocides, that are used to protect the system from damage or contamination. These additives may not be suitable for human consumption and may have adverse effects on health.
What contaminants may the hot water from the water heater or boiler contain?
The hot water from the water heater or boiler may contain various contaminants, depending on the source and quality of the water, the type and condition of the plumbing system, and the settings and maintenance of the water heater or boiler. Some of the common contaminants that may be found in the hot water are:
- Lead: Lead is a toxic metal that can cause damage to the brain, nervous system, kidneys, and blood cells. Lead can leach out from old pipes, solder, faucets, or fixtures that contain lead, especially when the water is acidic or hot. The EPA says there is no safe level of lead and recommends that the lead level in drinking water should be below 15 parts per billion (ppb).
- Copper: Copper is a metal that is essential for human health, but too much copper can cause nausea, vomiting, diarrhea, stomach cramps, liver damage, and kidney failure. Copper can leach out from copper pipes, fittings, or valves, especially when the water is acidic or hot. The EPA recommends that the copper level in drinking water should be below 1.3 parts per million (ppm).
- Iron: Iron is a metal that is also essential for human health, but too much iron can cause stomach upset, constipation, or hemochromatosis, a condition that causes excess iron to accumulate in the organs. Iron can leach out from iron pipes, tanks, or water heaters, especially when the water is acidic or hot. The EPA recommends that the iron level in drinking water should be below 0.3 ppm.
- Manganese: Manganese is a metal that is also essential for human health, but too much manganese can cause neurological problems, such as tremors, muscle spasms, or Parkinson's-like symptoms. Manganese can leach out from manganese pipes, tanks, or water heaters, especially when the water is acidic or hot. The EPA recommends that the manganese level in drinking water should be below 0.05 ppm.
- Zinc: Zinc is a metal that is also essential for human health, but too much zinc can cause nausea, vomiting, diarrhea, or reduced immune function. Zinc can leach out from zinc pipes, fittings, or water heaters, especially when the water is acidic or hot. The EPA recommends that the zinc level in drinking water should be below 5 ppm.
- Chlorine: Chlorine is a chemical that is used to disinfect the water and kill bacteria and other pathogens. However, chlorine can also react with organic matter in the water and form disinfection byproducts, such as trihalomethanes (THMs) and haloacetic acids (HAAs), that can cause cancer, liver damage, or reproductive problems. Chlorine can also evaporate from the hot water and cause irritation to the eyes, nose, throat, or skin. The EPA recommends that the chlorine level in drinking water should be below 4 ppm, and the THMs and HAAs levels should be below 0.08 ppm and 0.06 ppm, respectively.
- Nitrates: Nitrates are compounds that are formed from the breakdown of nitrogen-containing substances, such as fertilizers, animal waste, or sewage. Nitrates can contaminate the water from agricultural runoff, septic systems, or industrial waste. Nitrates can cause methemoglobinemia, a condition that reduces the ability of the blood to carry oxygen, or nitrosamine formation, a process that converts nitrates into carcinogenic compounds. Nitrates can also interfere with the thyroid function and cause goiter or hypothyroidism. The EPA recommends that the nitrate level in drinking water should be below 10 ppm.
- Arsenic: Arsenic is a metalloid that is naturally present in some rocks and soils. Arsenic can contaminate the water from mining, smelting, or industrial activities, or from the erosion of natural deposits. Arsenic can cause skin lesions, cancer, cardiovascular disease, diabetes, or neurological problems. The EPA recommends that the arsenic level in drinking water should be below 10 ppb.
- Radon: Radon is a radioactive gas that is formed from the decay of uranium and radium in the earth's crust. Radon can contaminate the water from the groundwater sources or from the cracks in the pipes or the water heater. Radon can cause lung cancer, especially when it is inhaled from the air or the steam. The EPA recommends that the radon level in drinking water should be below 4,000 pCi/L.
The hot water from the central heating system may contain some of the same contaminants as the water from the water heater or boiler, as well as some additional ones, such as:
- Antifreeze agents: Antifreeze agents are chemicals that are added to the water to prevent it from freezing in cold weather. Some common antifreeze agents are ethylene glycol, propylene glycol, or methanol. Antifreeze agents can be toxic to humans and animals, causing symptoms such as nausea, vomiting, headache, dizziness, coma, or death. Antifreeze agents can also damage the kidneys, liver, or nervous system. The EPA does not have a specific standard for antifreeze agents in drinking water, but advises that they should be avoided or minimized.
- Corrosion inhibitors: Corrosion inhibitors are chemicals that are added to the water to protect the pipes, fittings, or the water heater from rusting or corroding. Some common corrosion inhibitors are phosphates, silicates, or polyphosphates. Corrosion inhibitors can be harmless or beneficial to humans, as they can prevent the leaching of metals or minerals from the plumbing system. However, some corrosion inhibitors can also cause scaling, clogging, or reduced water flow. The EPA does not have a specific standard for corrosion inhibitors in drinking water, but advises that they should be used appropriately and monitored regularly.
- Biocides: Biocides are chemicals that are added to the water to kill or inhibit the growth of bacteria, algae, fungi, or other microorganisms that can contaminate the system or cause biofilm formation. Some common biocides are chlorine, bromine, iodine, or quaternary ammonium compounds. Biocides can be effective or necessary to prevent the spread of diseases or infections, such as Legionnaires' disease. However, some biocides can also be harmful or irritating to humans, causing symptoms such as skin rashes, eye irritation, respiratory problems, or allergic reactions. Biocides can also react with other substances in the water and form toxic or carcinogenic byproducts. The EPA does not have a specific standard for biocides in drinking water, but advises that they should be used sparingly and safely.
Note: We use the US EPA (Environmental Protection Agency) as the reference for water contaminant limits but the EU and WHO offers similar guidance.
Why can you not cook with hot water?
Cooking with hot water is not recommended, as it can affect the taste and quality of your food, as well as your health. Some of the reasons why you should not cook with hot water are:
- Hot water may contain more contaminants than cold water, as we have discussed above. These contaminants can alter the flavor, color, texture, or nutritional value of your food, or cause food poisoning or other illnesses. For example, hot water may cause tea or coffee to taste bitter or metallic, rice or pasta to become mushy or sticky, or vegetables to lose their color or vitamins.
- Hot water may not be hot enough to kill all the bacteria or pathogens that may be present in the water or the food. This can increase the risk of foodborne infections, especially for raw or undercooked foods, such as eggs, meat, poultry, or seafood. The FDA recommends that the water temperature for cooking should be at least 71°C (160°F) for most foods, and 74°C (165°F) for poultry.
- Hot water may not be boiling when it comes out of the tap, even if it seems to be steaming. This can affect the cooking time and the doneness of your food, as well as the safety of your food.
Fun facts about cooking with hot tap water
Hot tap water ruins your pasta
- Did you know that using hot tap water to make pasta can make it mushy or sticky? This is because hot water can dissolve more starch from the pasta than cold water, resulting in a gummy texture. To avoid this, you should always use cold water to boil pasta, and add some salt to prevent the pasta from sticking together. ⁴⁴
Gwyneth Paltrow (Actress and lifestyle guru) cooks with hot tap water
In a video posted on her YouTube channel in 2019, Paltrow shows how to make a vegan mushroom soup using hot tap water. She says that she uses hot water because it saves time and energy, and that she does not worry about the quality of the water because she has a filter. However, some viewers criticized her for using hot tap water, saying that it is unsafe and unhealthy.
Conclusion about why you should not use hot tap water for drinking or cooking
In conclusion, drinking or cooking with hot tap water is not a good idea, as it can pose some health risks and affect the taste and quality of your food. Hot tap water may come from a water heater or a boiler, or a central heating system, that may not treat or filter the water as well as the cold tap water.
Hot tap water may also contain more contaminants, such as metals, chemicals, minerals, or microorganisms, that can leach out from the plumbing system or the water heater or boiler, or be added to the water to protect the system from damage or contamination. These contaminants can accumulate in the water over time and affect its safety, taste, smell, color, and nutritional value.
Hot tap water may also not be hot enough or boiling enough to kill all the bacteria or pathogens that may be present in the water or the food, increasing the risk of foodborne infections.
Therefore, it is always safer to use cold tap water for drinking or cooking, and heat it up to the appropriate temperature using a kettle, a stove, a microwave, or a cooker. This way, you can ensure that the water is safe, clean, and suitable for your needs.
