18 FEATURE
! NOTE: SANS 10252:1 states that no PVC pipe may be installed in above-ground applications. SANS 10252 / 2 allows for the use of uPVC pipes for waste and vent pipes as long as these comply to SANS 967!
Pipe class and pressure rating The pipe class or pressure rating determines the strength of the pipe and the conditions it is designed to handle. For pressure pipes, the class normally refers to the internal working pressure the pipe can withstand. Common examples include:
• Class 6 – 6 bar / 600kPa
• Class 9 – 9 bar / 900kPa
• Class 12 – 12 bar / 1 200kPa
• Class 16 – 16 bar / 1 600kPa
A higher pressure class generally means a stronger pipe with a thicker wall and a higher pressure rating. However, the correct class must not be guessed. It must be selected according to the design pressure, static pressure, pump pressure, possible water hammer, safety factor and engineer’ s specification.
For sewer and drainage pipes, the class may relate more to external loading conditions than internal pressure. These conditions may include trench depth, soil load, traffic load, bedding detail and compaction. A pipe installed below a driveway, road crossing, paved area or heavy loading zone may require a stronger pipe than one installed in a lightly loaded area.
Diameter The diameter of a pipe is the pipe size, normally measured in millimetres. In many PVC pipe systems, the stated size refers to the outside diameter of the pipe.
Common PVC pipe sizes include: 40mm, 50mm, 75mm, 110mm, 160mm, 200mm and larger for civil works.
The correct diameter depends on flow rate, pipe gradient, fixture load, hydraulic design, municipal requirements and the approved engineer’ s drawings. It is a serious mistake to assume that all pipes with the same diameter are the same. For example, a 110mm pipe may be:
• a sewer pipe
• a soil-and-vent pipe
• a stormwater pipe
• a drainage pipe
• or a pressure pipe
Each type may have a different wall thickness, SANS standard, class, jointing system and approved application.
Wall thickness is especially important where pipes are installed:
• underground
• below driveways
• below roads
• in deep trenches
• in unstable ground
• near foundations
• below paved areas
• or in areas subject to vehicle or structural loading
Using a pipe with insufficient wall thickness can result in cracking, deformation, leaking, sagging, collapse or complete system failure.
A PVC pre-installation checklist SANS standard
Confirm the correct standard for the application
Pipe type Confirm whether it is pressure, sewer, drainage, soil, waste or vent pipe
Diameter
Pipe class
Wall thickness
Fittings
Jointing method
Confirm that the size matches the approved drawings Confirm the pressure rating or load class Confirm suitability for pressure or external loading Confirm compatibility with the pipe system Confirm solvent-weld, rubberring, compression or other approved joint
Site conditions Confirm trench depth, bedding, ground conditions and loading
Engineer approval
Written variation
Inspection
Confirm that the approved engineer has reviewed the requirements Confirm written approval for any deviation from the drawings Confirm inspection before backfilling, closing or commissioning
Risks of installing the wrong pipe Using the wrong PVC pipe can cause serious technical and legal problems, including pipe bursts, leaks, sewer blockages, pipe collapse, poor drainage flow, failed pressure tests, failed municipal inspections, non-compliance with SANS standards, damage to property, rework and replacement costs, disputes between contractor, client and engineer, and possible liability for defective workmanship.
Background by Magnific. com
Wall thickness Wall thickness is the thickness of the pipe wall. It affects the pipe’ s pressure capacity, strength, durability and resistance to deformation.
For pressure pipes, a thicker wall usually allows the pipe to withstand higher internal pressure. For underground sewer and drainage pipes, wall thickness and pipe structure help the pipe resist external loads from soil, bedding, compaction, paving and vehicles.
In many cases, an incorrect pipe may appear acceptable during installation but fail later because it was the wrong class, wrong wall thickness, wrong SANS standard or wrong pipe type for the application.
Advantages of PVC pipe
• Lightweight
• Easy to transport
• Easy to install and work with
www. plumbingafrica. co. za @ plumbingonline @ plumbingonline @ PlumbingAfricaOnline August 2026 Volume 32 I Number 06