Installing a Tankless Water Heater

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Installing a tankless water heater - basic tips for homeowners. Find out how to install Rinnai, Noritz, Takagi, Bosch and other water heaters, tips, and recommendations.

This article is for homeowners who are planning to install a tankless water heater. If you experience any problem during or after the installation or have questions regarding the unit, the best will be to call a representative for that particular brand.

Must to do when installing a tankless water heater

Installing a tankless water heater shouldn't be too complicate and hard, as long as you follow all the codes, local and national, and manufacturer's instructions, found on the rating plate and manual.

Powervent tankless heaters are safe for the installation literally anywhere inside your home. They are designed with a sealed combustion with zero clearance to combustibles. Even with the increased safety, choosing the right location for power or direct vent models is a very important step.


  • Avoid rooms where chemicals, gasoline, and materials are stored as they can produce the flammable vapors.
  • Avoid rooms that might contain an excessive amount of dirt, dust, aerosols and other debris, which can clog the air vent, reduce the fan efficiency or damage the heater.
  • Install a tankless water heater so it provides enough space for the future service and maintenance.
  • Water heater designed for the outdoors should be installed only outside, in areas with the mild climates and preferable in the recess box.
  • Avoid installing a unit in an attic due to safety issues.
  • For the tankless installations at the higher elevation than designed, contact the manufacturer to confirm this application.
  • You can install a tankless water heater in the mobile or manufactured homes, only if it is certified for this application.

Gas requirements

When installing a tankless water heater, either Noritz, Rinnai, Takagi or any other brand, see the model description on the rating plate and read the manufacturer's instruction before installation. The rating plate carries information such as the gas type, electric rating, gas and water pressure. The type of gas has to match the rating plate, and the gas pressure should be within the specified range. If the pressure is below the minimum required, the heater won't perform properly. If the pressure is higher than the maximum allowed it can cause serious problems to the heater, your property and put you in danger.

  • Manual gas shut-off should be installed between the gas supply pipe and the heater.
  • Once the gas connection is completed and the air is purged from the gas pipes, check for the gas leaks by using the soap-water mixture.
  • Check the inlet gas pressure by using the manometer, if necessary.

The gas manifold pressure is factory set, so no adjustment is usually needed.

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Plumbing requirements

Install a tankless water heater where leakage won't damage your property. A drain pan under the heater is recommended as a way to protect the property against the water damage.

All tankless water heaters mentioned here, are designed for potable water heating where the recommended supply pressure is usually between 30 and 80 PSI and water connections are 3/4".

  • A manual shut-off valve should be installed between the cold water supply and heater. This type of valve can also be installed on the hot water side.
  • Install the thermal expansion tank if the water system is closed loop system.
  • Do not reverse the cold inlet and hot outlet connections.
  • Before installing a tankless water heater, flush the unit and purge all the air from water pipes.
  • Install a pressure relief valve with the discharge pipe.
  • Minimum water flow/pressure should be provided for the proper water heating.
  • Hot water heater temperatures are usually factory set at 120 F.
  • The tankless water heaters are not suitable for installation where the chemically treated water is used, such as spas or pools.

Electrical work

  • Follow the electric code requirements.
  • The tankless water heater must be grounded.
  • Install the remote controller if it is not provided.
  • Most of the tankless heaters are equipped with the freeze protection system that requires an electrical power to the unit.
  • When installing a tankless water heater (the US and Canada) keep in mind to check out the electrical specs from the manufacturer's instructions: i.e. Rinnai requires 120 VAC and 60 Hz from the properly grounded circuit.


  • Install a water heater as close as possible to the vent area.
  • The vent pipe must be easily removable and used only for the water heater.
  • Avoid long runs of the vent pipe.
  • The vent terminator should never be blocked. In a case of the vertical run, through the roof, the vent has to have a rain cap.
  • Avoid dips and sags.
  • Your tankless water heater must have enough fresh air for the proper combustion and proper ventilation of the flue gases. Use the recommended material and vent size, with no changes in diameter.
  • The vent system must be sealed airtight to prevent any leaks.
  • The exhaust vent should never point to an opening in a building, such as windows or doors or near any air intake devices.
  • Leave the proper clearances between the water heater and nearby objects.

Keep in mind that installation of a tankless water heater should be done correctly to ensure the safe and reliable water heating and valid warranty. Regular maintenance which includes cleaning, visual inspection and small service and replacement should be performed as written in the instructions.

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