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Quality Gas Geysers, Stoves and Heaters
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Types of Gas Geysers

There’s no single best type of gas geyser – the right type for your home comes down to four things.

  1. Hot water demand: Using one tap at a time (single-use), or running several at the same time (multiple-use).
  2. Water pressure: The minimum water pressure available, from very low gravity-fed pressure to municipal pressure.
  3. Battery or electricity: Battery ignition with no electricity, or a small electrical supply of just 45 watts.
  4. Indoor or outdoor: Where the geyser will be installed, as indoor installations require the a flue and ventilation.

The four types of gas geysers

Multiple-use application

With smarter technology these multiple application geysers are designed to run multiple outlets simultaneously by automatically adjusting the temperature to accommodate the water flow.

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1

Constant Temperature

This smart geyser automatically adjusts itself to the water flow. With multiple outlets running simultaneously your water temperature will always remain hot and constant.

2

Fan Forced

Our largest and most powerful range uses a built-in fan for efficient gas burning and safe venting, maintaining a consistent temperature even with several showers and taps running at once.

Single-use application

A single application geyser is designed to run one outlet at a time (An outlet can be either a shower head or a basin tap or a bath mixer). With these single-use geysers you cannot run the shower and basin simultaneously. This will disrupt your water temperature.

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1

Eco-Flow Low Pressure

Ideal solution for your off-the-grid location. Eco-Flow geysers work on very low water pressure, and can operate from restricted water supplies like gravity-fed tanks. They supply one tap or shower at a time.

2

Diaphragm Activated

Our simplest gas geyser, with manual temperature control. Diaphragm Activated geysers need good water pressure from a municipal supply or a pressure pump, and work well with mixer taps when correctly set. They supply one tap or shower at a time.

How do gas geysers work?

Unlike an electric geyser that stores a limited amount of hot water in a tank, a gas geyser has no tank and never runs out of hot water, provided you have gas. Open a hot tap and, as water flows through the geyser, the burner ignites and heats the water on its way to the tap. Close the tap and the burner goes out.

That’s what makes a gas geyser so energy efficient – it only heats water when you use it, rather than storing a tank of hot water and using energy to keep it hot.

Compare gas geyser types

  • Fan Forced (FF)
  • Constant Temperature (CT)
  • Low Pressure (LP)
  • Diaphragm Activated (DA)

  • Ability to function on low water pressure (municipal or gravity-fed)

  • Off-the-grid

  • Multiple-use Can be used on multiple outlets at the same time

  • Requires electricity but can run off an inverter/UPS

  • Solar compatible (further heats solar water)

  • Installed outdoors (with a weather box)

  • Installed indoors (with ventilation)

  • Camping (Indoors)

  • Camping (Outdoors)

  • Suitable for a bath

  • Automatically adjusts the temperature

  • Operates on natural or piped gas

  • FFFan Forced
  • 20L
  • CTConstant Temperature
  • 12L
  • 16L
  • 12L 16L
  • LPLow Pressure
  • 5L 8L 12L
  • 5L
  • 5L 8L
  • 16L
  • DADiaphragm Activated
  • 6L 8L
  • 8L

Types of gas geysers FAQs

There are four main types of gas geysers:

  • Constant Temperature,
  • Fan Forced,
  • Eco-Flow Low-Pressure and
  • Diaphragm Activated.

Multiple-use models:

Constant Temperature and Fan Forced models are multiple-use gas geysers, designed to supply more than one hot water outlet at a time.

Single-use models:

Eco-Flow Low Pressure and Diaphragm Activated models are single-use gas geysers, designed to supply one outlet at a time.

Choosing between them also depends on your water pressure, whether you want battery ignition or have electricity available, and whether the geyser will be installed indoors or outdoors.

The difference between low-pressure and standard-pressure gas geysers is the minimum water pressure the geyser needs to operate.

Very low-pressure models

Eco-Flow Low Pressure models can operate from just 15–25 kPa, depending on the model (a gravity-fed water tank about 1.5–2.5 m above the geyser).

Low-pressure models

Constant Temperature and Fan Forced models can operate from 25 kPa (a gravity-fed tank about 2.5 m above the geyser).

Standard-pressure models

Diaphragm Activated models need at least 50 kPa (about 5.1 m of gravity-fed tank height), so they are better suited to municipal water pressure or a pressure pump.

Gas geysers use gas to heat the water, not electricity, and most models use batteries to ignite the flame. Dewhot Fan Forced models are the only ones that need a small amount of electricity to power the ignition and fan.

Battery-ignited models don’t use electricity

Eco-Flow, Constant Temperature, and Diaphragm Activated gas geysers use battery ignition, so they do not need an electrical connection.

Fan Forced models only require 45 watts to operate

Fan Forced gas geysers require a 220V power supply but use only around 45 watts. They can therefore be powered by an inverter, solar system, generator, or a Fan Forced UPS backup battery.

All Dewhot gas geyser types can work in an off-grid setup, but your water pressure and available power determine which one is best suited to your property.

Low Pressure Eco-Flow models use battery ignition and can operate from just 15–25 kPa (a gravity-fed water tank about 1.5–2.5 m above the geyser).

Constant Temperature models also use battery ignition and can operate from 25 kPa (a gravity-fed tank about 2.5 m above the geyser), with the added benefit of supplying multiple outlets.

Fan Forced models need electricity, but only around 45 watts. This is low enough to run from an inverter, solar system, generator or Dewhot’s Fan Forced UPS backup battery. They can also operate from 25 kPa water pressure.

Diaphragm Activated models also use battery ignition, but need at least 50 kPa, so you’ll need sufficient water pressure or a pressure pump.

A Fan Forced gas geyser uses a built-in fan and requires a small electrical supply, while the other Dewhot gas geyser types use battery ignition. Fan Forced models are multiple-use geysers available in larger 20L and 30L sizes, making them suitable when several hot water outlets need to run at the same time. They use only around 45 watts, so they can run from an inverter, solar system or Dewhot UPS backup battery.

Choosing the right size

Gas geyser size is rated by how many litres of water it can heat per minute. For example, a 16L gas geyser can heat up to 16 litres of water per minute, depending on the incoming water temperature and how hot you want the water. That’s more than a 150L electric geyser’s whole tank in ten minutes.

Our gas geyser size guide walks you through the bucket test, so you can calculate your flow rate and pick the right model and size.

Single-use application
Multiple-use application
Geyser Buying Guide
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The logic tree is a tool that guides you through a series of questions to help find the gas water heater solution the would be most suitable for your individual home set up.

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