In terms of the National Regulations, SANS10252 -1 (water supply installations for buildings), Reduced Pressure Zone Back Flow Preventers must be installed in any installation where there is a risk of contaminated water or harmful substances being back-syphoned or flowing back into a potable water supply line.


The regulations state that Back-flow Preventers shall be installed in certain types of installations and buildings, for example: Medical treatment of people and animals, pharmaceutical or chemical research and manufacturing, dairies, nurseries, stadiums, abattoirs, combined fire systems etc.

For further information, refer to 7.4 of SANS 10252-1 ‘Preservation of Water and Water Quality’ where a full description of building types is listed and technical specifications and requirements are tabulated.



In accordance with SANS 10252:1 - Water supply quality 7.1.2 (f) the minimum temperature at which water may be stored in a Hot Water Cylinder or any part of a hot water distribution system shall be at least 55⁰ Celcius. (The reason for this will be discussed in the next ‘Plumbing Facts’ edition).


Now consider that at this temperature (55 ⁰ Celcius) first degree burns will occur in as little as 5 seconds and within 2 seconds at 60⁰C with second degree burns occurring within only 5 seconds at 60⁰ C.

With this in mind, plumbing systems  must be designed and installed in such a way as to alleviate scalding injuries as well as slipping and falling injuries in showers and baths caused by thermal shock i.e. sudden and radical changes in temperature.

The risk of such injuries which can easily and usually do lead to expensive and unnecessary liability claims is particularly high for operators of health facilities or any institution, caring for infants, disabled and senior citizens as well as any other public facility such as gyms and sports facilities to name a few.

The solution to the challenge is to install ‘Fail Safe’ type Thermostatic Controllers at the point of use or feeding a group of fittings within close proximity to one another. Ideally such thermostatic controllers should be set to dispense ‘blended’ water at 43⁰ Celcius which is a hot but comfortable showering temperature while the user still has the option of reducing the temperature by adjusting the standard terminal hot and cold water taps or mixer.

Installers and designers of hot and cold water reticulation systems are well advised to inform their clients of the associated risks and hazards of dispensing hot water at uncontrolled temperatures.



In accordance with SANS 10252:1 - Water supply quality 7.1.2 (f) the minimum temperature at which water may be stored in a Hot Water Cylinder or any part of a hot water distribution system shall be at least 55⁰ Celcius. The reason for this is that there are confirmed hazards associated with the storage of water at temperatures known to sustain growth of certain harmful bacteria.


One of these bacteria that can be particularly harmful to human health is the Legionella Pneumophillia Bacteria, the causative agent of Legionellosis, more commonly referred to as Legionnaires Disease, a respiratory disease caused by ‘legionellae’ the genus of which there is a wide variety of at least 43 known species. These organisms are opportunistic pathogens which cause an acute fulminating respiratory condition which can be fatal if not diagnosed and treated appropriately.

Legionella is contracted by the inhalation into the lungs of very fine airborne water droplets, spray or mist such as in a shower, bath or any other water dispensing device.

Since specific tests are required to positively diagnose and treat Legionella, patients are frequently misdiagnosed and treated for pneumonia resulting in dire outcomes.                                                                                            

Legionella organisms are found in the natural environment and live in soil and water in association with other bacteria and protozoa, especially in ‘biofilms’.

These organisms commonly colonise and thrive in potable plumbing systems where temperature ranges are ideal and the water is rich in nutrients.

Water Temperature Effects on Legionellae Bacteria.

At and below 20⁰ C Legionellae can survive, but are dormant. Cold water in storage tanks, piping etc should ideally be kept at or below 20⁰ C.

From the above it can be seen why the minimum temperature at which water shall be stored in a Hot Water Cylinder or any part of a hot water distribution system is at least 55⁰ Celcius. But this presents itself with a challenge in that scalding injuries become an issue which cannot be resolved by simply limiting the temperature to which water is heated and stored to a value below the ‘Scalding Range’.

The risk of doing this is particularly high for operators and organisations offering services to the public such health facilities, hotels, sports clubs and gyms etc.

Installers and designers of hot and cold water reticulation systems are well advised to inform their clients of the associated risks and hazards pertaining to the generation of hot water.

The solution lies in ensuring that water is stored and distributed at temperatures of at least  55⁰ C and addressing the possibility of Scalding Injuries by using Thermostatic Controllers.

See ‘PLUMBING FACT 2’ for explanations.



Because Municipal Main Water Supply pressure varies from area to area as well as from time to time, one of the primary and fundamental considerations for a well designed plumbing installation is to ensure that the static pressure supplying the water reticulation system of a building is controlled and regulated to an acceptable value.


The maximum acceptable value as stipulated in SANS 10252:1 is deemed to be 600kPa (6 bar) where
(Supply pressure considerations) of this document states the following:

‘If the supply pressure could exceed 600kPa in any general or combined installation, and unless otherwise required, a Pressure Reducing or Control Valve Shall be incorporated in the Service Pipe upstream of the first terminal water fitting, to limit such pressure to a maximum of 600kPa’.

The reason for this Regulation is simple. It is to alleviate high mechanical stresses and loads on the pipe work and associated valves and fittings thus ensuring the longevity of the installation while reducing future maintenance costs, noise and most importantly water losses due to mechanical failure of materials as well as damage to property.

To some extent it is also to prevent unnecessarily high water usage on the simple basis that the higher the system pressure the higher the flow-rate yielded at fittings.

The Regulations, under also states that ‘ In a combined installation where a fire boosting system is installed (see 7.3.4), all branches to non-fire related pipework (installations) shall be  protected by a Pressure Control Valve’ Meaning that if a single supply is used on a site to serve the fire system as well as the domestic system then all of the branches off of this line serving the domestic supply must be fitted with a pressure reducing or pressure control valve to protect the domestic installation.

It is also good and recommended practice to install a Pressure Reducing Station downstream of a pump set feeding a building from a water supply tank or reservoir. This is done to stabilize the downstream pressure and flow from the delivery pump set especially during pump start-up thus alleviating unwanted pressure surges and spikes in the service pipe feeding an installation.



That the National Building Regulations SANS 10400 are compulsory regulations that designers of buildings must adhere to and comply with when designing and constructing any form of building.


SANS 10400 by way of Regulation 14 of R509 (8 June, 2001) issued in terms of the Water Services Act also makes it compulsory for consumer installations to comply with SANS 10252:1 (Water supply installations for buildings) as well as SANS 10254 (The installation of fixed electric storage water heating systems) and other SANS Codes of Practice that need to be complied with when it comes to the design and installation of water supply systems in buildings of all types.

SANS 10252:1 gives reference to recommended best practise as well as mandatory compliance for plumbing installations from the water meter to the final user terminal fittings and everything in between such as water supply tanks, pump sets, hot water generation plants, material specifications, hydraulic design, pipe size selection, application of materials, water quality, safety and fit for purpose designs and installations amongst many other aspects of plumbing design.

With the above in mind, every person involved in either plumbing design or installation should be or become acquainted with this document, SANS 10252:1, and understand the application of the principles and theories contained therein.




SANS 10400 – National Building Regulations – PART XA (XA204) States that “At least 50% of the annual average hot water heating requirement shall be provided by means other than electrical resistance heating including but not limited to solar heating, heat pumps, heat recovery from other systems or processes and renewable combustible fuel.”


This means that when hot water generation plants for buildings of all descriptions are designed, the designer must prove by reasonable calculation that at least 50% of the energy used to heat the annual volume of the hot water requirement is done so by a renewable energy source and not an electrical element. Gas and coal are not renewable energy sources.

SANS 10252:1 (Water supply installations for buildings) Tables 2 and 5 give guidance to hot water demand, storage volumes and energy requirements for hot water generation systems and plants for different types of buildings.

To a large extent this regulation has changed the way that hot water generation installations are designed and installed. With the need to comply with the 50% energy rule it has become common practice to employ central Bulk Hot Water generation and storage plants where localised Heat Pumps or Solar Panels (or any other renewable energy source) can be integrated into the storage vessels.  for buildings such as blocks of flats, student accommodation, clinics etc, instead of individual ‘geysers’ being installed for each flat or group of fittings requiring hot water.

From the central bulk hot water storage plant hot water is circulated by way of circulation pumps throughout the building via an adequately sized hot water circulating ring at temperatures of between 55⁰C to 60⁰C. (Refer to Plumbing Fact  2 & 3). Exposed pipe work comprising the circulation ring as well as any branch off of the ring must be adequately lagged using approved insolation material with R-Value of 1 for pipes with an internal diameter of 80mm or less and an R-Value of 1.5 for pipes with a diameter greater than 80mm. This is to ensure that minimum energy is lost due to radiation. Ideally not more than 5⁰C should be lost in any circulating ring.

In the next edition of Plumbing Facts we will discuss some the considerations that are required to design and install an efficient hot water reticulation circulating distribution ring.