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TECHNICAL
DEAD LEGS!
SANS 10252-1 (7.7.1.3) states:
Unless stated otherwise, the length of an unheated pipe (dead
leg) conveying hot water directly from a fixed water heater to
a terminal water fitting, or from a point of take-off from a hot
water circulating system (ring) to a terminal water fitting, shall
be such that the internal volume of that pipe does not exceed
four litres.
Example
15mm copper (litres per metre: 0.150): 4ℓ divided
by 0.150 equals a length of 26.66m
Volume of pipe (internal diameter) = π × r2 × length
Exposed hot water pipes must always be lagged. The
reason for this is obvious: to save water and energy.
August 2018 Volume 24 I Number 6
Weight/mass
Water possesses a specific weight (mass). A cubic metre of
water at a temperature of 4°C weighs and therefore has a
mass of 1 000kg. (Water has a specific gravity of 1.)
Practical application
This will remind you that the structure supporting
any tank or hot water cylinder having a mass in
excess of 300kg shall be designed and signed off by
an engineer.
It will also remind you that when installing geysers,
the structure supporting the weight of the cylinder
must be done in accordance with SANS 10254.
(See article on page 43 of the May 2018 issue of
Plumbing Africa). PA
www.plumbingafrica.co.za