Is Siphonic Suitable for Podium Drainage?

Siphonic for Podium Green Roof

Q: Is siphonic suitable for podium drainage?

Yes, in some circumstances. However based on our experience, we’re more likely to recommend gravity drainage to the podium area.

In our experience drainage of a podium area is better addressed with a gravity system. To this end we would often propose a Hybrid Solution utilising:

  • Siphonic Drainage to the main roofs and
  • Gravity Drainage to the podium drainage.

Let’s look at the 3 main influencing factors for going with gravity drainage system in a podium scenario: 

  • 1.
    Rainfall Intensity
    A podium slab is not bound by the same rainfall intensity requirements as a roof (unless fully enclosed). As a result, we can utilise smaller diameter gravity pipework in a podium scenario than would be possible for standard roof drainage.
  • 2.
    Area can be too small to drain effectively with siphonic
    Podium slabs often have sunken planters or ACO drains either situated lower than the main podium or draining only a very small area which may be too small for siphonic drainage. It would be inefficient to utilise a siphonic system to the large podium areas & supplement it with a gravity system to the smaller areas. Instead, a single gravity system from the podium is generally more cost-effective.
  • 3.
    Location of termination point
    Depending on the location of the termination point, there may not be sufficient downpipe to allow us build-up a head of water to prime the siphonic system effectively.

There are circumstances where a siphonic system might be preferable in a podium area, so it’s essential to look at the project holistically. Here at Capcon Engineering, we’re big advocates of siphonic drainage; however, as Rainwater Roof Drainage Specialists, our approach is always non-biased. We continually strive to develop the best, most efficient rainwater drainage solution for each individual building: siphonic, gravity or hybrid.

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