Natural hot water springs found in many parts of the world are known as ‘Geysers.’ Appliances generating hot water have also acquired the same name.

Geysers are available in the following types:

(A) Pressure – Type Geysers –

These geysers are kept under pressure of a water mains supply or an overhead tank. The pressure allows hot water to be distributed to a number of points, gener­ates good flow in taps and showers, and permits mixing of hot and cold supply through a mixing fitting.


A cold-water inlet is placed at the bottom of the geyser and outlet at the top. Whenever hot water is drawn into the system, an equivalent amount of cold water enters displacing the hot water used. This keeps the geyser always filled up with water, thus eliminating the danger of the geyser emptying and the heating elements burning out.

(i) Storage-type Pressure geysers –

Permit a longer time for heating up the water before period of non-use. An electric heating element of lower capacity can thus be used.

The vessel must be so constructed as to withstand the pressure it is subjected to.


Pressure-type geysers can burst or collapse due to explosion if incorrectly installed. An understanding of the principles governing its working can prevent such accidents.

(B) Non-Pressure Type Geysers –

A non-pressure-type geyser is similar to the pressure-type in its shape, except [hat it has a single outlet which displaces hot water when the valve on the cold water is opened.

The geyser remains full of water and is provided with a thermostat It can be installed on any water supply system, (e.g. overhead tank, direct supply, etc.) and does not require a vent pipe or vacuum breaker.


(C) Instaneous Type Geysers –

These are available in pressure (multi point non storage) and non-pressure types. The latter are, however, more commonly available in India.

(ii) Instaneous type non pressure type geysers require a heating element word around a pipe which heats the water to a temperature matching the rate of flow. The heating element has to be of a higher capacity, with greater power load. The geysers have to be constructed from sturdy materials to ensure safety As the pipe through which water passes is of a very small bore (6-8 mm diameter), it is likely to choke from deposition of scales if the water is hard.

Safety Features of Geysers:


Dangers of Expansion:

(a) Water, when heated expands. At 65-70°C the expansion is about 3-5% of its original volume at ambient temperature. The increased volume increases the pressure within the fixed volume of the geyser, straining it structurally.

(b) The boiling point of water increases with pressure.

(c) All pressure-type geysers are controlled by an automatic thermostatic switch which cuts on and off at pre-set temperatures. They operate at a differential temperature of 10-12°C and cut out at 65°C (The temperature settings are adjust­able).


(d) If the water supply is from an overhead tank installed at a height of 20 m, the pressure in the heater will be 2 kg/sq cm and the boiling point of water 132.6°C.

(iii) Storage heat non pressure type.