In our regular Master Plumbers’ Series, our technical advice team shares the answers to some of the most asked questions. For our Winter Edition, Aaron Bridger takes on some of the...
Its important to consider ground movement when laying underground drainage as Master Plumbers technical expert, Sam Welsh explains.
Laying sanitary drains under concrete slabs creates potential issues, particularly in areas with unstable or highly reactive soil types. Information necessary to protect against movement of the ground-damaging pipework should be found in the approved plans for the construction and will be related to the soil type.
Unstable ground conditions can be found on sites designated as H1, H1-D, H2, H2-D, E, and E-D. If you are uncertain about the ground type, a soil test or consultation of the construction plans for your new build can provide clarity.
A method of protection against this ground movement is to use a flexible joint, commonly known as a swivel joint.
An example of where to install
Swivel expansion joints should be installed 800mm apart at 1:40 grade before entering under or through a footing or slab. And they should be as close as practical to the slab or footings edge. This will allow the branch or drain to move with the building if it is required to do so. (figure 2)
Notes: Swivel expansion joints and expansion joints should be installed at 50% of their telescopic movement. Swivel expansion joints installed on grade should not be used to correct pipe misalignment.
One swivel expansion joint shall also be installed on a vertical riser as close to the underside of the slab as practicable. (figure 3)
Note: Swivel expansion joints installed on vertical risers should have a minimum of 75mm telescopic movement.
By following these examples on how to use expansion swivel joints, you can ensure that your plumbing systems will remain functional and reliable, even in the face of unstable ground conditions. Swivel expansion joints are essential components for any construction project dealing with challenging ground types in Australia.
Stay ahead of potential issues and protect your drainage systems by
incorporating swivel joints into your plumbing design.
For other examples and ways to use swivel joints check manufacturers installation instructions.