large sewer siphon

[willemeulen]

Busy with a designing a rising main for sewer. Bumped into another sewer outfall and thought it was a pump line as well. Informing with the the service authority (counsel) they told me it is a siphon!? I've seen siphon's in cases where gravity sewer needs to pass another gravity service like storm water. But if this thing is a siphon as they indicate it,s 1.6 km long, crossing a small valley including little stream, elevation difference is about 10 - 15 meters from start to finish and it low point is approximately 40 meters lower as starting point.

Anybody have experience with such big siphon's?

 

[bimr]

Something like that would probably be considered to be a force main.

 

[coloeng]

Haven't seen these in the wastewater sector before, but have seen many in the irrigation systems and raw water systems in the western US. They are commonly called inverted siphons, because they aren't a true siphon. As OP indicated they are used to cross small valleys.

 

[rconner]

Sewer siphons (and in practice perhaps most are "inverted siphons") are discussed in ASCE/WPCF MOP No. 60/FD-5, and probably its precursor ASCE et al MOP No. 37 before that). As you can read there and in other references, there are many aspects to consider (perhaps particularly in wastewater services).
They have indeed been many siphons also used for some water services, and I remember a 1500mm(60") one a few years ago installed just outside Moquegua, Peru, as part of a quite lengthy aqueduct/water delivery system from the Andes. While extremely long and quite effective aqueducts, and even some siphons, were known to the ancients (and concepts were actually tweaked with some modern spins for that particular job) the ancients had some understandable difficulties locating routes across deep canyons. Modern cementlined ductile iron pipe was used by the designers there, for this purpose to traverse a deep valley where a river flowed.