Faq
QWhat kind of roof can be applied on the siphonic system?
Curve roof, Parabola roof, Cone roof, another roof with irregular shape, Roof garden, Landscape, Vertical wall.
QWhat are the differences between conventional and siphonic drainage systems?
To answer this question let’s look at conventional drainage first: Most downpipe systems have a very inefficient method of discharging water from roofs, as water spirals down around the inner walls of the pipe with an air column in the centre. During drainage, the water in a conventional downpipe never exceeds a third of the pipe capacity, due to this air presence and its effects. Siphonic drainage works very differently. Special siphonic roof outlets prevent air entering the pipes with only a small amount of water covering the outlet. The downpipe backs up (primes) and the gravity force pulls the water through the downpipes at high velocity. This high velocity creates friction loss within the pipe, which results in a negative pressure situation or vacuum, hence the rainwater gets sucked into the downpipe.
QWhat are the main benefits?
- Smaller pipe diameter (less materials, lower cost).
- Further overhead horizontal runs are possible.
- Under-slab piping is reduced significantly or eliminated.
- Cost of excavation, backfill, and compaction is reduced significantly.
- The depth of rain retention ponds or tanks is reduced.
- Higher operating velocities contribute to effective interior cleansing.
- Flexible gutter design without limitation of downpipe locations.
QIs there any special maintenance required for siphonic drainage systems?
No. The piping system is effective at cleansing itself due to the flow patterns developed within the system. There are no moving parts or devices requiring maintenance or replacement. All roof drains are subject to the same environmental conditions including debris from trees, industrial activity and wildlife activity. Therefore, regular and appropriate roof and gutter maintenance is always recommended.
QHow the cost varies for Siphonic drainage system compare to a traditional drainage system?
Siphonic Roof Drainage System is in fact normally less expensive. Savings of 25 to 45% are often attained due to the significant reduction in underground drainage requirements together with the associated pipe installation and trench work (excavation, soil treatment, bedding, pipe laying, test, backfill, compaction, further backfill, and re-test costs.)
QWhat type of buildings can use Siphonic drainage system?
This generally depends on the location and design rainfall rate. A building with a roof area of collecting 80 liters per second or greater will normally achieve commercial benefits. However, smaller roof areas have been drained using a Siphonic Roof Drainage system to achieve the technical benefits.
QWhat is wrong with traditional gravity system?
The performance of Traditional gravity drainage systems is restricted by a number of factors. These include: The driving force is the depth or ‘head’ of water above the roof drain, The gradient available to allow the water to flow for horizontal pipe leading to multiple downpipes and large amount of below ground drainage. Gravity drains largely require ⅔ air to transport ⅓ water. Vortex formation on vertical gravity pipes results in the water being transported in a spiral motion rather than straight through the pipe. The above factors result in an extremely inefficient drainage solution.
QHow does a siphonic system terminate?
The Siphonic Roof Drainage system terminates either by connecting to a suitably vented gravity drain or manhole chamber/connecting pit which should be sized to cater for the discharge from the Siphonic Drainage System.
QWhat makes the siphon occur?
It is simple Hydraulics that makes the Siphonic Roof Drainage system function. The height of the building provides the energy and as the small diameter pipes prime and the full bore plug of water reaches the vertical downpipe; the water accelerates due to the forces of gravity. This acceleration creates negative pressure behind the plug which gives the system its Siphonic title and the forces generated literally suck the water off the roof until the rainfall event abates.
QWhat does Siphon mean?
It is used to refer to a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted 'U' shape, which causes a liquid to flow upward, above the surface of a reservoir, with no pump, but powered by the fall of the liquid as it flows down the tube under the pull of gravity, then discharging at a level lower than the surface of the reservoir from which it came.
QWhat type of pipe works required for Siphonic drainage system?
Any pipe work that is suitable for carrying the volume of water at the design flow rates with the resulting negative pressures. For commercial reasons cast iron, PVC Schedule 40 solid core or stainless steel (careful selection of jointing method required), etc. can be utilized.
