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Engineering Area

sifonika area ingenieria 1Sifonika provides design and consulting services through a highly specialized team with a cumulated experience in the desk drainage sector for over 10 years.


Our Technical and Management Team has personally participated in the design and management of the siphonic system of such iconic works as the T4 Barajas, Expo Building in Caja Magica in Madrid, Logistics C. of IKEA in Valls, Fira of Barcelona, Airbus hangars in Seville and Illescas, Altas Palmas Complex in Seville, Parador Atlantis in Cadix, The wind tunnel in Bilbao, Hislabor in Valladolid, Palacio Congresos in Coruña, Coca-Cola Silo in Madrid, etc..


sifonika area ingenieria 2 More and more we face a combination of three factors that make the use of technically and technologically advanced solutions in the evacuation of storm water from buildings essential.


Rain intensities have increased and alternating periods of drought followed by torrential rains with great destructive power occur more frequently. This phenomenon associated with climate change should be taken into account when designing a protection cover.


Especially in countries like Spain where rainfall intensity parameters established by the CTE must always be considered as a minimum implementation. I.e., meet the minimum according to the CTE may be insufficient in many cases if you stick to the actual experience of short and intense rainfall (generalised "cold drop" or "new climate") that are happening in Spain with increasing frequency.


This "new climate" is the way we want to bring the focus on the problem of adapting the designs to the real climate data that a building will face throughout its life: we do not intend to discuss the existence of climate change but alert to adequately project the actual exposure which the buildings face.

•    New buildings, be they logistical, industrial or infrastructure tend to have higher vain and greater pending on desks, which increases in direct proportion the flow to evacuate and the necessary evacuation speed.

•    An unstoppable trend towards eco-sustainability of buildings takes us to recycle rainwater increasingly. The siphon system, with its inherent ability to concentrate the flow evacuated at one point, is the reference system and in all countries where there is a clear awareness of the need to capture and exploit rainwater.

sifonika area ingenieria 3These factors, together with the known and traditional advantages of the siphonic systems in relation to the greater protection they provide to the roof, the absence of pending of their collectors and the large decrease in the number of downpipes, total meters and diameters of pipes to be used, make that such systems are an option increasingly used for all types of building.


From Sifonika we propose two ways of action designed especially for designers and the world of prescription:


1.- Free training seminars that can be taught in person or digitally (webinar). We are happy to further in explaining the siphonic system and help resolve all doubts that may arise in relation to the use of siphonic systems.


2 - A free "Express Service" of preliminary design and quote of a price for our first "turnkey" service in less than 24 hours that includes all aspects of the system from its technical conception to installation and warranty, going through all intermediate stages of detailed engineering, supply, prefabrication and Project Management.



How The Siphonic System Works

 sifonika como funciona sistema sifonico

Unlike a gravity drain system which mixes air and water by the vortex effect, the siphonic evacuation, which is also called depression evacuation, full section or induced vacuum, prevents the air to enter in its conducts as a consequence of the known "Coriolis effect".


This absence of air, which is achieved for relatively low thresholds of rainfall intensity, produces a physical suction phenomenon: the water is immediately "suctioned" from the downpipe and occupies 100% of its useful section, so the system must be calculated at full pipe. The siphonic design induces an hydraulic piston in the vertical or downpipe, which is the "natural motor" of the system.

This phenomenon is caused by the Bernouilli theorem, which proves the conservation of the total energy of the water in the downpipe. Thanks to this effect, the siphonic system can provide an extremely high drainage capacity by using pipes with a much lower diameter. This is due to the high speeds of evacuation achieved using the siphonic effect. That is, if the flow must always be equal to section per speed, it is clear that the same flow can be evacuated by different values of the two factors, and in the particular case of the siphonic system, a lower section implies higher fluid speed.


To induce siphonic action two basic conditions must be met:

- Surface of the liquid to be evacuated above the point of discharge.

- Avoid air entry into the pipe.


The role of anti-vortex device of outlets is to prevent the entry of air and thus it gets "speed up" the process of priming the system.


The self-priming outlet is therefore a key part of the system because it "sucks" the water in the guttering, preventing the entry of air. The pipes are sized considering they will work at 100% capacity, from the roof to the ground level, according to the current design, which gives an idea of the importance of the right choice of this parameter by the designer of the building.


Being the whole pipe full of water from the gutter to the collection point, the hydraulic piston is the full height of the building, opposite the spout height which would act as a conventional piston. A higher energy resulting in evacuation speed much higher than the traditional or conventional gravity system.


The full section flow allows to use all the building height as hydraulic charge where the negative pressure in the water column of the vertical pipe accompanies the siphonic function having its maximum point of depression in the upper side of the downpipe and gradually moving to experience positive pressures in the lower section once the vertical stretch finish.


The hydraulic load entails an increase in the speed of water higher than 7 m/s (1.5 m/s would be maximum for a gravity system) which results in a considerable reduction of the whole piping system.

Calculation Formulas:
Bernoulli Continuity Equation:
h1,h2 = height in which points 1 and 2 are placed.
ρ1/γ, ρ2/γ = pressure in points 1 and 2.
V21/2g, V22/2g = flow pressure
ΣH1-2 = hydraulic losses between points 1 and 2

It is deduced:
Δh1-2 ≥  ΣH1-2
The height difference between collection and discharge must be greater than the hydraulic lost.

Calculation of diameters using the Colebrook-White's formula


It is important to highlight that the fact of functioning with pressure also in the inferior collector section (normally buried or pending from slabs below the discharge elevation plants) has a substantial advantage, which is the absence of pending, and therefore saving in excavation costs or loss of size (or gauge) in case of devising by a lower plant.


This has particular impact in areas of high water tables or bedrock and also in large car parks in shopping centres or logistics buildings, for example.



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C/ Pinar, nº 5.
28006 Madrid. España.
Telf: (+34) 91 745 68 69