What to consider before buying a gas geyser?

Gas Geysers are a bit of a confusing topic. We understand though, the name itself can be confusing. Gas geysers can also be called gas water heaters, since unlike the traditional geyser that acts as a reservoir for your water heating it over time - gas geysers do not store large amounts of water internally. Rather, gas geysers heat water on demand. This means that they are only heating water when your hot water tap is turned on.

In this article we are going to try to answer some of the common questions we get around gas geysers and we are going to address some of the technical aspects that you should consider before buying a gas geyser or gas water heater for your home.

How does a gas geyser work?

As mentioned above, the name gas geyser can cause some confusion. Some people refer to them as Gas Water Heaters, this is a more fitting name since that's exactly what gas geysers do - they heat water using a gas flame. The water is pumped through a radiator which is heated up using gas. There is no storage tank inside the geyser so water is only heated when it is flowing through the unit.

A certain flow rate is required to trigger the gas ignition.

Understanding flow rate

Gas geysers typically operate within a flowrate range. For example, a 12L gas geyser may operate between 6L/m and 12L/m. Flow rate is quite simply the volume of water moved through a pipe per minute. Using our example of a 12L gas geyser, this gas geyser is capable of heating up to 12L of water every minute. On the flip side, it is only capable of heating a minimum of 6L a minute. Hence, the range of 6 - 12L.

Flow rate should not be mistaken with pressure. Flow rate is determined by 2 things: Your water pressure and the diameter of the pipe. For example, if you have a 1cm diameter pipe and a 10cm diameter pipe, both with 6bar pressure. The 10cm diameter pipe will obviously have a higher flow rate.

I am unsure which gas geyser to get

Don't worry! We get this question a lot, we can phone you back, just fill in the form below and one of our project assistants will get in touch with you for your free consultation

What size geyser should I get?

This depends entirely on what you are using it for, the layout of your house and how many hot water taps you expect to have on at any given time. A bath will require a geyser of 12 - 16L and a shower about 6L/min. We have included a helpful graphic below that will help you establish what you may need to consider:

table explaining what size gas geyser is appropriate for different applications

Is one gas geyser enough for my entire house?

Graphic demonstrating how to chain multiple gas geysers together to supply an entire house.

Yes, but there are few things you need to consider:

  • It depends on the distance from the gas geyser to the places of application.
  • You can run two bathrooms off one geyser but they need to be within 10m of the gas geyser.
  • If the run is greater than 5m from the geyser you should install another unit.
  • If your bathrooms are both within 5m of the gas geyser but your kitchen is further you can use one gas geyser for your bathroom and a smaller one for the kitchen.

If you are still unsure, here is a video from Dewhot: 


The bucket test - The foolproof way of figuring out what size geyser you need.

  1. Get a large bucket, preferably about 20L and run water into for 60 seconds from the tap where you are wanting hot water (Shower, bath etc. ).
  2. After exactly 60 seconds turn off the tap and then measure how much water is in the bucket.
  • This will give you an accurate gauge of how many litres flow through your tap in 1 minute and thus what size geyser you need to consider.

Here is a helpful video by dewhot on how to perform a bucket test:

Can I install my own gas geyser?

While we don't doubt that you have the skills necessary to install a gas geyser - The South African Law requires that a SAQCC Gas qualified installer must install the gas geyser for you. This is primarily for your protection. If you choose not to comply with this law you are not only immediately rendering your warranty null and void, but more importantly, putting your and your families safety at risk.

I am still unsure about something

If you are still unsure about something, or something in this article did not make sense, please do reach out to us using the contact details below. We would love to assist you in making the best decision possible when buying your gas geyser:


010 593 4542

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