Home Tech Important Criteria for Choosing Gas Tankless Water Heater

Important Criteria for Choosing Gas Tankless Water Heater

by Jajce d Muckic

Gas water heaters are reliable, functional and safe devices that meet the demand for hot water. Their selection is huge. They all look the same at first glance, but upon taking a closer look at these devices made by US, European and Chinese manufacturers, you could see that they differ by a whole list of qualities.

Probably, the most important criterion for choosing an electric tankless water heater is its power. But any store consultant can help you choose the heater by its power parameter in a matter of minutes. In this article we are going to review some obvious but not the least important choice criteria. If you prefer to go straight to selecting a particular model, we recommend checking out this review.

The Type of Ignition System

According to CosyHousehold.com, the type of ignition system is a pretty significant parameter in any water heater. It will affect how often you will need to come to the device to keep it running, as well as how safe and cost-efficient the process of obtaining flame will be. So, gas water heaters may have several types of ignition:

  • Piezo ignition is an improved version of the manual method. The spark appears with a press of a button. With its help, the pilot burner lights up (as in the case with the manual method). It is burning all the time, even being in a standby mode. When someone turns on the hot water, the main burner lights up, and after shutting off the hot water, it goes out. Due to the fact that the pilot burner constantly maintains the flame, it is not considered cost-efficient. But it is not expensive and completely energy-independent.
  • Electric ignition. Gas supply and the process of burning occur only when somebody turns on the hot water valve. So, the gas is being preserved. When they shut off the valve, the access to the gas is being blocked with a special gate, and the burning stops.


Water heaters with electric ignition can be divided into two types: energy-dependent and energy-independent. In energy-dependent types the ignition system is connected to an electrical outlet. If you live in an apartment and do not experience any particular problems with electricity, then this is quite a good option for you. In energy-independent electric water heaters, the ignition can work from:

  • Batteries. They recommend using powerful alkaline batteries and changing them regularly; lowering power supply voltage can cause particular cracking noise when the burner starts working.
  • Hydrodynamic ignition. The energy sufficient for ignition is obtained with the help of a small hydro generator. As soon as you turn on the hot water, the motor starts rotating and the energy for ignition starts accumulating, which takes only a few seconds.

The Type of Combustion Chamber

If you want to get a gas water heater, you need to pay special attention to a lot of technical details, and the type of combustion chamber is one of the most important parameters here. There are only two options:

  • Open combustion chamber;
  • Closed combustion chamber.

Heaters with open combustion chamber are the simplest and the cheapest. They use the air from the room where the device is located. The air intake occurs through the holes at the bottom of the heater. Such units are mounted in the kitchens or in separate utility rooms (a great option for owners of country houses). Combustion products are drawn out through the chimney by a natural draft. Such devices feature the minimal noise level during their operation, but they are more suitable for country houses, as they require connection to the chimney. Besides, it is necessary to ensure good ventilation in the room where the heater will be installed.

Heaters with closed combustion chamber get air from outside. The chimney in these units is horizontal; it discharges through the wall and has a form of a coaxial pipe (the pipe in the pipe). Through the inner part of the pipe, combustion products are discharged with the help of a fan, and the air is supplied through the outer pipe to the heater. You can install such a heater in any room, it is safer, but you will have to pay more for it, and the operation of the fan depends on the electricity and is accompanied by a slight noise.


The Type of Heat Exchanger

Durability and wear resistance of the water heater is directly related to the material the heat exchanger is made of:

  • Steel heat exchanger is inexpensive, pretty heavy, and is relatively reliable. It is better to choose a model where the heat exchanger is made of stainless steel;
  • Highly-refined copper resembles steel by its basic properties, but it features higher heat output, therefore, it will be possible to get the maximum benefit from each cubic meter of gas;
  • Regular copper is heated unevenly – impurities are the main reason for it. That is why many manufacturers cover the heat exchanger with heat-resistant paint, but it can only delay the destructive processes in the heat exchanger temporarily.

So, the best options to consider are stainless steel and refined copper


Water and Gas Pressure

Each water heater technical data sheet contains two basic parameters of water pressure: the minimal one, when the unit turns on, and the ultimate – the pressure that the heat exchanger can withstand without losing consistency. It is advisable, before choosing a gas water heater, to clarify all the parameters of your water supply system.

High pressure can become destructive to the water heater, and water hammers, unfortunately, are not uncommon. Purchase units that are able to withstand a short-term increase in pressure in the system up to 11-12 bars.

The Type of Burner and Power Modulation

Burners in gas water heaters can be of two types:

  • with continuous power. It is the easiest option; the main advantage is that it is cheap. If you change water pressure, you will have to manually change the temperature in the water heater, which can eventually become hectic. If you do not change the temperature, the water can be way too hot.
  • with modulated power. Everything is much more modern here. You just need to set up the desired water temperature, and the power of the flame will be regulated depending on the pressure of the water. It is a more preferable option. Of course, the water temperature control is a part of any water heater, but conventional devices cannot adapt to pressure and gas pressure changes, and units with modulated power will, under almost any conditions, produce water with set parameters. Such heaters are more expensive, but are not only more convenient in operation, but also more cost-efficient.

Of course, a modulated power burner will be more preferable.