Tip & How-To about Plumbing

Legionella, Legionnaire's, Hot Water Heaters and Mixing Valves

Many people are turning their hot water heaters down to dangerously low temperatures to try to save fuel or energy. What they do not know is that they are playing a very dangerous game with a deadly disease.

Your water heater can be a very deadly incubator for the deadly Legonella Bacteria. In an effort to save money a lot of people have made the decision to turn the water temperature on their water heater down to very low temperatures. Temperatures of under 140F can allow the bacteria to grow in your hot water heater.
The way to combat this problem is to make sure that the temperature for your hot water heater is over 140F. The problem that is caused by those temperatures is that 140F water can be dangerous because of the risk of scalding. This risk is especially high for young children and older adults.

The question then becomes, what do you do to make sure that either of these problems are not a risk in your home. The answer to this question is to install a device called a mixing valve.

The mixing valve mixes some cold water with the hot water coming from the hot water heater. This mixing valve takes the temperature of the hot water down to a temperature that will not hurt people with tender skin. A water temperature of under 120F will give people time to react to hot water before it hurts them. The cooler water in the piping going to your faucet will not have the time to grow bad bacteria before you use it.

To review the thing you need to remember about this problem. Keep your water in your heater higher than 140F to keep the bad stuff from forming. You want the water coming out of your faucet needs to be under 120F to keep from scalding people in your home. And, a mixing valve will do the job of cooling off your water to a safe temperature.

If you are thinking of turning your water temperatures down be careful. Check into installing a mixing valve instead and keep your family safe.

Posted by on

Plumbing Logo

Related Topics:

Related Questions:

2 Answers

Do rinnai heaters run efficiently if turned up and down often?


Maintaining the lowest acceptable setting and leaving it at that temperature is the most economical way to run the unit. If the space is going to be unoccupied for an extended time (several hours), lower temperatures are okay. This minimizes the need to burst the heat to warm the space quicker. As I understand your unit, it minimizes electrical & gas consumption by basing the need on the temperature difference of actual space temperature and setpoint. The larger the gap, the more power and gas is consumed.
In summary, when the space is occupied, maintain a consistent temperature setting. When the space is unoccupied, maintain a lower setpoint.

Hope this helps. Good Luck. :-)

Feb 15, 2010 | Rinnai RHFE-1004FA 38,400 BTU Energy Saver...

2 Answers

water is not hot enough


What a great energy saver response....run water through another tap in the house in order to fill the pipes with hot water! I have the same problem; cannot even get WARM water in my tub. I have 2 solutions: #1, on my incoming water pipes are regular faucet handles which I am going to attach a hose on the hot side that will reach into the washer and manually mix the temperature. #2, purchase an old refurb washer at a used appliance store that HAS a hot-water setting and hope they will take the "wonderful, new energy saver" as a trade. There are just some times you really need HOT water. I can't imagine washing diapers in cold, although I haven't had to do that in many years. Energy saving factory settings: capital "B", capital "S"!!!

Mar 30, 2009 | Washing Machines

2 Answers

On-Demand Water Heater


An on-demand, or tankless, water heater is a system for heating water as it passes through the pipes, usually very near the point of use. Traditional tank water heaters bring the water to approximately 140 degrees Fahrenheit (60 C), in order to ensure the water supply lasts long after the heater turns off. Since this is obviously far too hot to be pumped out of a shower of faucet, cold water is added to the mix in the pipes. Coupled with the loss of thermal energy over time, the average tank heater has an efficiency of approximately 80%. On-demand water heaters have a number of advantages over their tank-using counterparts. While tanks often degrade over time and begin leaking, the apparatus used in an on-demand water heater is much less susceptible to the burdens of age, and will often outlive the house they're installed in. The amount of energy used is a fraction of that used in a tank water heater, due to increased efficiency and a much smaller window during which a heating source is in use. While tank hot water heaters can, and often do, run out of hot water after a number of showers, on-demand heaters provide a never-ending supply of hot water, ensuring that warm water is always available when needed. A tankless water heater can cost between $500 and $1500, and they most commonly use either electric or natural gas energy to heat the water. Most mid-sized households report an energy savings of approximately 25-45% for a gas or propane heater, and up to 50% with an electric heater, over using traditional tank heaters. Water is usually set to a maximum temperature of 120 degrees Fahrenheit (49 C), though many heaters allow for custom setting of the maximum temperature via remote control. Outflow rates range from 8-14 gallons (30-53 litres) per minute. Installation for most tankless water heaters is incredibly easy, involving simple plumbing. In the case of electric heaters, all that is required for a fuel source is to plug the heater into an outlet and begin heating your water. Some modern on-demand water heaters can incorporate a solar preheating system. This system uses a traditional solar heating system and tank to bring the water nearer to the desired temperature, saving substantial energy use in the final on-demand heating. A solar preheating system costs between $500 and $800.

Aug 27, 2008 | Stiebel Eltron CK20E Electric Tankless...

Not finding what you are looking for?

507 people viewed this tip

Ask a Question

Usually answered in minutes!

Top Plumbing Experts

Donni Steen

Level 3 Expert

659 Answers

Brad Brown

Level 3 Expert

16194 Answers

Tom Chichester

Level 3 Expert

36408 Answers

Are you a Plumbing Expert? Answer questions, earn points and help others

Answer questions

Loading...