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Tankless Water Heater Installation Tips. Things to Consider

Tankless water heaters are a long-term investment in continuous hot water and energy savings. To get the most out of them, you and your plumber need to keep certain factors in mind from the outset.

If you’ve always used a storage tank water heater, switching to tankless technology demands careful review of several critical factors. Here are six items to consider when making the switch and consulting with your contractor:

Size your tankless right

Your plumber will need to determine how to size your unit. The type of tankless water heater chosen for any given application will depend on 1) incoming water temperatures throughout the year, and 2) the water-use patterns of the home’s occupants.

In short, the water heater will need to be able to handle the coldest possible incoming ground water temperature in your area, so your plumber will calculate that and subtract it from the desired temperature to determine the maximum temperature rise, or “Delta T,” over a 12-month period.

He or she will then need to calculate the maximum flow rates of all the hot-water water fixtures in your home and add them together. Your new tankless unit should be able to meet the demands of every fixture in your home, even if they were to run at their maximum flows all at once.

With that information in hand, your plumber can figure out which tankless model is right for your home.

Check the gas supply

Typically, for a given application, tankless water heaters use more gas than their storage-tank counterparts to meet the sudden demand for hot water without storage. Your plumber must confirm that your home has sufficient gas pressure to allow the unit to meet all your gas needs.

Next, he or she should determine whether the gas line is adequately sized to supply enough gas to the water heater. A typical tankless water heater will need a ¾-inch gas line. However, if there is sufficient pressure and the run length is short enough, a ½-inch line may be sufficient with certain tankless water heaters, such as the Noritz EZ Series. Just be sure your plumber accounts for all the appliances on the gas line, not just the water heater. Installers should verify gas requirements and sizing with local licensing rules and codes.

Meet air requirements

Like any water heater, a tankless unit needs enough incoming air for the combustion process to operate properly and efficiently, thus maximizing energy savings. Many units are vented directly, drawing air for combustion from the outdoors. Others, depending on climate, can be installed outside. Check with your plumber to determine the best solution for your application.

Don’t go too hot

Once the unit is installed, the hot-water setpoint temperature should be only slightly above the highest temperature needed for domestic uses. Typically, shower temperatures are the highest, at 104°F to 106°F. You don’t really need to go warmer, and doing so could increase the risk of accidental scalding.

If you’re worried about germs, don’t. Unlike storage tank-type water heaters, which can be susceptible to Legionella bacteria growth (Legionnaires’ disease), tankless water heaters store no hot water where bacteria can form. In fact, tankless water heaters continuously flush any internal water with every use.

Plan to maintain water quality

Water quality is an important consideration for all water equipment, and water heaters will often be impacted the most. Of particular note is water hardness, a measure of the minerals (magnesium and calcium) it contains. When heated, these minerals tend to precipitate out of the water and form crystals, called limescale, which can coat pipes.


The limescale acts as an insulator, reducing heat-transfer efficiency (the fraction of heat energy that moves from the burner to the water). Limescale can also increase thermal stress, which can ultimately shorten the lifespan of the water heater.

Limescale can be removed on a regular basis through a process called descaling, in which you flush vinegar through the water heater’s heat exchanger coils to remove the buildup. Ultimately, it’s important to know the local water quality and take steps to either treat household water or establish a maintenance plan.

Deal with condensation

If you’re installing a high-efficiency, condensing tankless water heater, a by-product of its combustion process is an acidic condensate that must be handled appropriately before the water moves to the home drainage system. Check local building codes for safe disposal procedures: A neutralizer may be required to protect the plumbing inside the home.

Focusing on these six factors while planning your tankless installation will help you enjoy efficient, on-demand hot water for years to come.

For more information, please visit www.noritz.com.