[Tagging] Question about waterway=pressurized

[Volker Schmidt]

Here in the Po Valley we have hundreds (or mor) of inverted siphons. They
do not need and, to my knowlege, do not have pumps. Many or max be most of
them are not (yet) correctly tagged in OSM. This most likely due to the
fact that waterway data are imports and it looks as if the original did not
distinguish between waterway junctions and underpasses.
I am not aware of any example of an uninverted siphon.


On Tue, 14 Sep 2021, 17:42 François Lacombe, <fl.infosreseaux at gmail.com>
wrote:

> Hi Volker
>
> From my understanding, both siphon and inverted-siphon are pressurised.
> Siphon uses suction to pull water downstream which implies a positive
> pressure in its middle, without air.
>
> This is an interesting concept we could classify with additional tags
> dedicated to siphons.
> Some pumps use this principle to raise level of a liquid (see
> pump_mechanism=siphon
> https://wiki.openstreetmap.org/wiki/Key:pump_mechanism)
>
> Do you have real example of working siphon please?
> I only seen inverted siphons (mainly for sewage under roads or rivers) in
> the past.
> This is the bottom of an inverted siphon (maybe 3m in diameter) to make
> water cross a valley https://www.openstreetmap.org/way/405871631
>
> All the best
>
> François
>
> Le mar. 14 sept. 2021 à 17:12, Volker Schmidt <voschix at gmail.com> a
> écrit :
>
>> Question to François: is an inverted-siphon (botte sifone, pont-siphon)
>> piece of waterway to be mapped as pressurised?
>>
>> On Tue, 14 Sep 2021, 16:18 François Lacombe, <fl.infosreseaux at gmail.com>
>> wrote:
>>
>>> Hi Kyle,
>>>
>>> Le mar. 14 sept. 2021 à 03:24, Kyle Hensel <K.y.l.e at outlook.co.nz> a
>>> écrit :
>>>
>>>>  Is there are reason why waterway=pressurized is used instead of
>>>> waterway=river/stream/canal/drain and pressurized=yes?
>>>>
>>>
>>> Yes, waterways are defined according to their permanent flowing regime.
>>> Some are free flowing, others are pipe flowing.
>>> A given waterway can't be both as it requires a special prerequisites to
>>> handle pressurised water.
>>>
>>> https://wiki.openstreetmap.org/wiki/Waterways#Artificial_waterways:_pressurised_vs_Open-flow_Waterways
>>>
>>> This table gives all values according to their regime
>>> https://wiki.openstreetmap.org/wiki/Key:waterway#Values
>>>
>>> River, streams, canals and drains are defined as free flowing waterways,
>>> so it wasn't consistent to propose pressurised=yes for them.
>>> If a river goes punctually in a permanent pressurised culvert,
>>> waterway=pressurised + tunnel=culvert sounds the most appropriate
>>> possibility.
>>> By the way, a river relation can obviously involve sections with
>>> different regimes.
>>>
>>> In a perfect world we would have cleared waterway=* from all other
>>> values than flowing regime (move waterway=pier or waterway=fuel to man_made
>>> or amenity).
>>> Never mind, I go back sleeping :)
>>>
>>> All the best
>>>
>>> François
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