56 TECHNICAL
Underground vs above-ground pipes and fittings
By
IOPSA
IOPSA( Institute of Plumbing South Africa) has compiled a short document explaining the fundamental differences between underground( UG) piping and soil-vent system or above-ground( SV) piping, and why the two should be used absolutely correctly.
Many plumbers do not understand how different the two are, and installation requirements are often neglected. It is imperative that the pipes meet the SANS requirements before installation occurs.
Below are just a few key points explaining the differences, as well as why UG piping systems cannot be used above ground: 1. The basic differences between the pipes and the fittings are the colour and the thickness. UG piping is manufactured in a cream / beige colour and SV piping is white. The SV piping also may have a wider inner wall to that of a UG pipe.
2. As per the requirements of the relevant SANS standards, the pipe and its fittings are tested as a complete system and will be required to operate as such. So, although you can connect a beige UG pipe with the white SV fitting and the system may work, it does not comply with the required standards. Thus, the installation will not be compliant.
3. Fittings and angles required on the installation: a. UG piping and fittings are manufactured for below-ground use only, as the fittings are calculated for the correct slope as required in an underground installation. b. SV piping and fittings are manufactured for a system above ground, and the fittings are cast for horizontal and vertical installations to provide the correct gradient on the slope as required from SANS 10252-2.
4. As per SANS 10252-2, the correct piping is required to be used in above-ground installations. The only PVC piping that is SANS approved for above-ground use is the white SV piping and fittings.
5. UG piping is not UV resistant and becomes very brittle in sunlight. Plumbers make the mistake of thinking it can be used in an above-ground duct or stack; this is incorrect as per point 1. The pipes and fittings are tested as a unit and if you use the incorrect piping with the SV fittings, the installation will not be compliant to SANS installation standards. It is clear in SANS 10252-2 that the above-ground piping needs to be used for duct work.
UG bend at 92.5˚. SV bend at 95.0˚.
September 2017 Volume 23 I Number 7 www. plumbingafrica. co. za