TECHNICAL
59 b.
c.
d. any water installation conveying potable water to any drain or sewer; any water installation pipe and any service pipe upstream from any backflow preventer installed in terms of 7.4.3; and a general installation and any fire installation when they are supplied through separate communication pipes.
Photos by Richard Bailie
This section also has rules surrounding when pumped connections are included in the design as well as water meters.
Subsection 7.4.3 is called“ Prevention of Backflow” and is the best place to start if you want to have a good idea of when you would require backflow prevention:
7.4.3.1 Adequate measures shall be taken to prevent the |
back-siphonage of water into the following: |
A. a communication pipe from any of the following water installations: |
1. |
a fire installation or combined installation; |
2. |
a general installation serving any of the following activities: |
i. |
medical treatment of people or animals; |
ii. |
medical, pharmaceutical or chemical research and |
manufacturing; |
iii. |
agriculture, including dairies and nurseries; |
iv. |
laundering and dry-cleaning; |
v. |
photographic processing; |
vi. |
metal plating; or |
vii. |
treatment of hides and skins; |
3. |
a general installation serving any of the following locations: |
i. |
mortuaries; |
ii. |
abattoirs; |
iii. |
sewage purification plants; |
iv. |
refuse pulverizing works; |
v. |
harbours; |
vi. |
oil processing and storage facilities; |
vii. |
wineries, distilleries, breweries, yeast and soft drink |
factories; |
viii. |
sports fields; or |
ix. |
any other premises on which an activity is carried out |
that can affect the potability of water; and |
b. maintenance operations, or when fire-fighting is in progress nearby, or because of a burst water main); or the downstream pressure exceeding that of the supply.( This is for example possible in an installation such as a heating system, an elevated tank, and a pressure producing system such as a boiler. In the case of a fire installation, non-potable water carried in a fire tender can be introduced into the installation via a pumping connection.)
7.4.3.2 To prevent the possibility of backflow of water in any of the
water installations as given in 7.4.3.1, or in any other case where such a possibility exists, and unless other approved measures have been taken, a. a storage tank shall be installed such that 1. the entry of water into the storage tank is solely from a pipe that discharges at a height, above the flood level rim of the tank, of the greater of at least 75mm and twice the nominal diameter of such pipe; and
2. water required for any activity that can pollute the water supply is withdrawn only from the outlet of such storage tank, or b) appropriate backflow prevention measures shall be selected from those listed in column 1 of table 12, for the degree of the potential hazard contemplated in column 2 of table 12.
An RPZ discharge.
B. an installation, in all cases where
1. the design of terminal fittings installed( including any hose bibcocks, laboratory taps or movable shower units) is such that a hose or any other flexible pipe can be attached to the fittings, 2. fire hose reels are installed in a combined installation, 3. an underground irrigation system can provide contact between polluted water and water within the installation, or 4. any other fittings can provide contact between polluted water and water within the installation.
NOTE: Backflow can be caused by the following: a. the development of negative pressure or the lack of pressure in a water supply system( i. e. when a main is drained for
7.4.3.3 Unless other approved measures are taken to prevent the backflow of water from terminal water fittings that discharge water into a sink, wash-hand basin, bath or other similar appliance,
a. such terminal water fittings shall be so installed that the vertical distance between the point of discharge of the fitting and the spill-over level of the receiving appliance is at least equal to the distance given in table 13 for the size of the fitting concerned;
www. plumbingafrica. co. za September 2018 Volume 24 I Number 7