Tankless Water Heaters

Tankless water heaters are the standard system to heat water for potable use and to heat homes in Europe and most other parts of the world. They can help you save energy and $$$ and provide an endless supply of hot water when needed and only when it is needed.

You can buy these tankless water heaters from Our Sponsor - PexSupply.com
A Takagi tankless water heater.

Unlike a tank type water heater, hot water is not "stored" and does not have to be kept hot even when it is not needed. The water in these systems is heated at the time of its use. Turn on the faucet and the tankless heater produces the required amount of hot water. Turn off the faucet and the system stands-by until more hot water is needed. Need a small amount of hot water or a great deal of hot water? The tankless heater will heat just the amount of water needed.

I have used tankless water heaters while visiting in Europe and have wanted to have them in the US. Thanks to PexSupply.com I now have a Takagi Tankless heater at our weekend home and can report about its installation and use.



  • When the hot water faucet or valve is turned on in any part of system, the tankless unit detects the water flow and the burner is ignited. The burner heats the water as it flows through a coiled pipe. Water is heated as long as the unit detects a water flow. As soon as the faucet or valve stops the water flow the burner is extinguished and the tankless unit stops heating water and using energy to heat water.

    Tankless units are available in natural gas, LP/propane and all electric models. The size of the unit determines how much water can be heated, to what temperature and at which rate of flow. Properly sized unit(s) are designed to provide an adequate amount of hot water for a specific home or business.

  • Tankless water heaters have several advantages and its high time that we have started using them in the US. Water heaters are one of the highest energy consuming appliances in a home and tankless units are a very good way to reduce energy consumption.

  • Tankless heaters don't waste the energy to keep a tank of water heated. They only heat the water that is needed at the moment. You will not be heating water needlessly!
  • Tankless water heaters produce as much water as is needed. If you have a bunch of guests in the home who like to take long hot showers, no problem the tankless heater will produce water as long as is needed. You will not "run out of hot water".
  • Tankless water heaters take less space than the tank-type models.
  • Cost: tankless water heaters cost more to purchase than the tank-type models and are a bit more complicated to install. This extra cost is likely to be offset by the lower cost to heat the water in your home.

  • Tankless systems are more complicated than tank type water heaters. They are also newer to the US market and there are not as many plumbers who have a lot of installation experience with these systems. The good news here is that I have found the online and phone support from Bosch and others to be very good!
  • Best time to install: tankless models require somewhat different installation practices than the tank type models. For example, most units require a 3/4" gas line and a condensate drain line. So its best to install such units in new homes. Installing them in existing homes may require some modifications.
  • You may find that it takes a bit longer for the hot water to reach the faucet. This may result in a limited amount of extra water usage. You may use a bit more water but are likely to save energy.
  • People may take longer showers because the supply of hot water is endless. But you may notice that it is a little trickier to adjust the shower valves for the even desired temperature.
  • I had intended to install my tankless heaters by myself but ran out of time. So my tanks were installed by my HVAC contractor. During this process I did read the installation instruction, observed the process and kibitzed with the installers. Here are a few tips:

      1. As always, read the instructions carefully! The instruction are shipped with the heater or can be found on line. For example:
      2. Assume that the installation practices for tankless units are different than those for tank type units.
      3. Locate the tankless heater in accordance with your needs and the installation requirements. For Example:
          -a place where venting, combustion air, fuel and plumbing systems will be easiest install, -a location closest to your major hot water usage points, -an area with the required clearance to combustible surfaces and other appliances (see your installation manual).
      4. Make sure that you get a unit that is rated for the type of gas at your home - LP or natural gas.
      5. Some tankless units can by used for potable water as well as radiant heat. Others are not designed for such dual use.
      6. You are working with gas, electricity and combustion air. Respect these factors.
      7. This job requires some real skills in gas and water plumbing and venting.
      8. Most units require a 3/4" gas supply. This includes the main pipe and the flexible pipe at the unit.
        a 3/4" gas connection

      9. Most units require stainless flues.
        A stainless steel side-wall vent

      10. Most units require an outside combustion air source.
      11. One of the main gas combustion by-products is water vapor and most of these units require a condensate drain line to dispose of this excess water vapor.
        A condensate drain

    And no matter if you are going to install a tankless heater or are working on some other project, please use good tools. Buy them, borrow them or rent them but please use the right tools for the job. The wrong tools and poor quality tools are often dangerous and will prevent you from completed the job in a workmanlike manner.

  • When a shower or other faucet is located some distance from a tankless heater it may take a bit longer for the water to reach the desired temperature. InExample of a Taco D'Mand Installation order to save this water, a re-circulating pump can be installed under a nearby sink. Such a system diverts the cold water back into the supply system until the hot water reaches the pump and then shuts itself off. A manual or programed switch is used to activate the pump. The best systems employ a local and/or remote switch for activation. See the Taco D'Mand Systems carried by our sponsor Pex Supply