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Hot tap water FAQ

Hot tap water FAQ

Can tap water really cause serious burns?

Yes. Most Canadian hot water heaters are set to a temperature of 60°C (140° F). Water this hot can severely scald a child's skin in just one second.

A scald is a second-degree or third-degree burn caused by hot liquid or steam. Hot coffee, tea, soup and other hot foods are the most common causes of scalds to young children. Hot tap water is a less common cause, but these scalds are often more severe – and they are easy to prevent.

To prevent tap water scalds, the hot water at all your taps should be no hotter than 49°C (120°F). At this temperature, it takes about 10 minutes to burn a child's skin.

Tap water scalds can happen anywhere that the water is too hot – not just in the bath. Children have been scalded by hot tap water when playing at the sink, or by putting their hands or feet into a bucket filled with hot tap water for household cleaning.

Why are children more at risk?

Hot water thermometerChildren are more at risk for tap water scalds because:

Elderly people and people with certain disabilities or medical conditions (such as diabetes) are also at high risk for tap water scalds. This is because their skin may not be able to feel heat quickly or because they cannot move away from hot water quickly.

How can I find out the temperature of my hot tap water?

Use a thermometer that can show high temperatures, such as a meat or candy thermometer. Or you can use a special testing card for hot tap water. These are available from some public health offices. Run the hot water tap for two minutes. Make sure the tap is turned to the hottest setting. If you have used a lot of hot water in the past hour, wait two hours before you do this test. Fill a cup with the hot water. Put the thermometer in the cup. Wait 30 seconds and look at the temperature. If it is higher than 49 C (120 F), you need to lower your water temperature.

How can I lower the temperature of my hot tap water?

Lower the temperature of your hot water heater. The easiest way to prevent burns from hot tap water is to turn down the setting on your hot water heater to 49 C (120 F). Do this only if you can easily see the thermostat dial on the outside of the tank.

If you choose this option, there are some important things you should know:

Read the manual for your water heater before changing the setting on the thermostat dial. If you do not have a manual, contact the company that made the water heater. Their number should be posted on the heater. If you rent your water heater, contact the rental company.

Install mixing valves to control the temperature of your hot tap water.

Devices called mixing valves or tempering valves can be installed in the plumbing pipes at various places. These valves control the temperature of the water before it leaves your taps. Inside your water heater, the temperature can be scalding hot, but the valve will mix in cooler water if needed, to ensure that water at the tap is no hotter than 49 C.

Talk to a qualified plumber or the rental company for your water heater for proper installation of mixing valves.

There are three ways you can use mixing valves:

The cost of installing mixing valves will depend on how many you install and whether there is other plumbing work or renovations going on at the same time. One valve costs may cost in the range of $100 - $150, not including labour.

If you do not have access to your water heater:

Turning down the thermostat of large water heaters in multi-unit buildings is NOT recommended. Harmful bacteria can grow in large water heaters set too low. Also, there may not be enough hot water for everyone in the building.

If you live in an apartment or multi-unit building and do not have access to your hot water heater

What other devices are available to help prevent tap water scalds?

Some other devices available include:

Anti-scald or shut-off devices: These are products that attach to the faucet or tap. Some models actually replace the faucet. If the water gets too hot, these devices slow down the water to a trickle. You can restart the water by mixing more cold water into the tap.

Anti-scald devices are available in safety specialty shops, some hardware stores, and some children's product stores. They cost about $10 to $50, depending on the type of product. Not all models fit on all kinds of taps, however, and although these products are promoted as "do it yourself" items, they may require adapters or the help of a plumber to install them.

Tap guards: A tap guard blocks your child's access to the hot water tap. These can be found in many home improvement and child safety stores.

Does lowering my hot water temperature increase the risk of bacteria infection in my house?

A concern often raised about lower water temperature is the risk of bacterial growth – particularly legionella. Legionella is the organism that causes legionnaires' disease, a form of severe pneumonia. These bacteria live naturally in ponds, streams and rivers, and also grow in indoor plumbing systems – mostly in hot water tanks.

Many things affect how much legionella will multiply and whether they create a health risk for people. These factors include:

Legionella does not pose a risk to drinking water. To make someone sick, the bacteria must be inhaled through water droplets. Many people have been exposed to legionella and do not get sick.

Most people should have no health concerns about lowering their hot water temperature to 49 C (120 F). Please note these important precautions:

If you have an electric water heater, do not lower the thermostat setting below 60 C. Legionella grows more often in electric water heaters because of the way they are designed. You can install mixing valves instead. Any adjustments to electric water heaters should be done by a qualified professional.

Do not lower the thermostat of your household water heater below 49 C. Legionella grow best when the inside of the heater is less than 49 C.

If anyone living in your home has a long term or serious illness, check with your doctor before turning down your water heater. Do not lower the thermostat setting of your water heater if anyone in your home has health conditions such as:

If you have any concerns about legionella, you can protect your family from tap water scalds by installing mixing valves instead.

What about my dishwasher? Don't I need very hot water to clean the dishes?

Makers of dishwashers and detergents often recommend that hot water should be 60 C for their products work effectively. However, tests show that dishwashing detergents will perform with good to excellent cleaning results at temperatures as low as 38 C.

When dishwashers operate with hot water at 49 C, some water spotting on dishes may occur. Parachute suggests that preventing scald burns from too-hot tap water should have higher priority than the need for spotless glasses. You can wipe glasses with a clean dish towel to remove spots. As an alternative, many newer models of dishwashers have internal temperature boosters. Incoming water is heated quickly to help clean the dishes. This feature adds about $45 to the price of a dishwasher.

Will the water be hot enough for my cleaning and bathing if I lower the temperature of my hot tap water?
Household cleaning and bathing do not need water temperatures hotter than 49 C. For example:

Source: Canadian Food Inspection Agency. Food Safety Tips for the Kitchen – Fact Sheet.

Will I run out of hot water more quickly if I lower the thermostat of my water heater?

This is not likely to happen. In a survey conducted five years after the Washington state government required household water heaters to be set at 49 C, three-quarters of people who had lowered their hot water temperature reported no concerns about their supply of hot water.

If you often run out of hot water, it is more likely that you need a water heater with a bigger tank to meet the hot water demands in your household.

Will I save money on energy costs if I turn down the thermostat of my hot water heater?

According to Environment Canada, hot water tanks account for 14 per cent of home energy use. Only home heating uses more energy. Lowering the setting of your hot water heater from 60 C to 49 C will reduce your heating bill, but some of this saving may be offset by an increase in the amount of hot water you use. In the end, you will likely see modest savings, in the range of $30 to $40 per year, possibly higher if energy costs rise. Insulating your hot water tank can also save up to 10 per cent on your energy use for heating water.

Our child has asthma. Don't we need very hot water to help get rid of dust mites in her bed linens?

Allergens produced by live dust mites, which commonly live in household textiles such as bed sheets, clothing and curtains, are one of the main causes of allergic disease. The Asthma Society of Canada recommends that clothing and bedding be washed in water at least 55 C to kill dust mites and their allergens.

Instead of using very hot water, there are several options. A dust mite control additive can be used in a low-temperature wash. Dust mites will also be killed by drying fabrics at a high setting for one hour.

If you need to use very hot water for laundry in order to kill dust mites, you can still lower the hot water temperature in all other areas of your household. Mixing valves to control hot water temperature can be installed in the hot water pipes for all areas except the clothes washer. 

What are the building regulations if I live in Ontario?

As of Sept. 1, 2004, the Ontario building code requires that hot water at household taps be no hotter than 49 C. The code change applies to new construction and substantial changes to existing plumbing, such as the replacement of water heaters or hot water faucets.

Title: Ontario Building Code Change 2004: English

Where can I find information from Quebec?

English (Summary):
Prevention of scalding and legionellosis associated with hot tap water in private homes

French (Full document): 
Prévention des cas de brûlures et de légionelloses assocïés à l'eau chaude du robinet dans les résidences privées, 2e édition