Solar Advantage

Thermosyphon Solar Hot Water Geyser Installation

When the solar hot water geyser is installed on the roof at a lower position than the electric geyser, the water in the electric geyser will circulate through the solar hot water geyser and back into the electric geyser. This is a natural phenomenon called thermosyphon. The natural rising of the hot water creates pressure in the loop and the water will circulate between the two geysers.

Installation Requirements:

  • A retrofit installation kit.
  • A steel frame if the solar geyser is mounted on a flat roof.
  • Tile roof hooks if the geyser is mounted on a tile roof.
  • IBR or corrugated roof hooks if the geyser is mounted on an IBR or corrugated roof.
  • Retrofit Installation guide.

Thermosyphon Installation

The retrofit thermosyphon type of installation is very similar to the standard retrofit installation the only difference being that because the solar hot water geyser is mounted below the existing electric geyser, we may make use of the thermosyphon effect.

The benefit of the pre-feed setup is still applicable as the electric geyser’s element will heat the water for the first time in the electric geyser, when water is drawn off from the electric geyser the electric geyser will be fed with hot water from the solar geyser.

The retrofit installation kit which may be ordered with the solar geyser comprises of the following:

  • T.P Relief Valve (temperature and pressure relief valve).
  • Non-Return Pressure Reducing Valve.
  • Vacuum Breaker.


  • Copper piping and connections.
  • Element for heating water on sunless days or during the evening.

The solar hot water geyser must be installed in a north, north-west facing position, please read our article on solar geyser placement for more details.

With this type of retrofit installation (see diagram above), the cold water supply passes through the non-return pressure reducing valve (PRV) into the solar hot water geyser at the bottom of the unit.

Within a couple of hours of exposure to the sun the water in the solar geyser will be heated and will flow through the hot water outlet at the top of the solar hot water geyser to the cold inlet of the existing electric geyser thus filling the geyser with hot water and eliminating the need to use its electric element.

Vacuum breakers prevent water from being siphoned backward into the water system and protect water geysers against vacuum conditions. A vacuum breaker typically contains a plastic disc that is pressed forward by water supply pressure and covers small vent holes. Should the supply pressure drop, the plastic disc springs back opening the vent holes, letting the outside air into the system thus preventing the backflow of water or a vacuum forming.

The T.P. relief valve (temperature and pressure relief valve) is a safety valve that is set at 80º Celsius (Temperature) and 200 Kpa (Pressure), the valve will release water from the geyser if the pressure rises above 200kpa or the temperature rises above 80º Celsius.

When hot water is drawn from the system, the water will flow from the solar hot water geyser to the electric geyser and out through the tap, the moment the tab is closed, the water will continue to circulate between the solar hot water geyser and the electric geyser making use of the non-return valve as shown in the diagram above.

If you would like to order a solar geyser or solar geyser installation or if you have a question about solar hot water systems or our company, contact us on the numbers below or Click Here to use our contact page as we’d love to hear from you and look forward to assisting and welcoming you as one of our valued clients!

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