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Pipe Networks: Auto Structure In/Out based on inverts.

Pipe Networks: Auto Structure In/Out based on inverts.

Instead of requiring that I tell C3D which pipe is OUT (on an attached structure), make it so that the one with the lowest invert is automatically treated as the "Out" connection.  The last time I checked, water will leave via the lowest elevation.


If the OUT invert of one structure is LOWER than the invert at the other end of that pipe, then put up an error telling the user that.  But if a structure has several pipes connected, it should be obvious which pipe has a lower invert.


If all the connected pipes have the same invert, then look at the invert elevations at the OTHER ends of those connected pipes.  Which one is lower?  THAT one is the out pipe.  Again if no pipe appears to be an "OUT PIPE" then put up an error.


I'll upvote this because I think it's a good idéa. Although there are special cases when you have more than 1 outlets from a structure. This week i'm working on a stormwater network where one structure has 1 outlet below the inlet level and one above the inlet level. The upstream pipe is larger than both the outlets - so at heavy rain the first outlet is filled and thus the water level rises inside untill the second outlet invert is reached.

Special case for sure - but still 🙂


I agree this needs help.

But @doni49 here's the question: what are you trying to accomplish? How does  the program treat IN versus OUT connections? What would you like to be able to do that you can't do currently?

I know what the answer is for me, but I think I use this a little differently than others. So I'd like to know what is it for you.



Just to mess with your head a little, I have a sanitary manhole in a subdivision I'm working on with three outgoing pipes. There are no pipes flowing into it, this manhole is just a three-way top end. All three have different inverts. How should the program handle that?


You've definitely got me stumped on that one. I guess it would need to
allow you to Override the settings that I'm suggesting.

But as far as "what am I trying to accomplish" goes: I just seems
counter-intuitive to have the software even CONSIDER the notion that the
pipe with the LOWEST invert would be identified by default as the in pipe.

When we are modeling an existing system based on a survey and measure downs, we find more often than we like that pipes were laid flat or reverse sloped or that inlet elevations are slightly lower than outlet elevations, and that is just the truth of how things get built in the real world.  I wouldn't want my 'intelligent' software trying to tell me which pipe it thinks is the in and the out solely based on elevation because I know which way the water is actually flowing, even if it's not the ideal way.


On the design end of things, we also end up designing structures where the out is higher than the in for water quality or storage purposes, or where a pipe will have a reverse slope for various reasons.  We already have upstream and downstream control, as well as start and end control, and I've never needed anything more than that if I've managed it all correctly.


I'm not suggesting that C3D make it so that the pipes CAN'T go at the wrong slopes (the issue of needing to model an EXISITNG drainage system is a perfect example as to why that would be a bad idea). 


I just think that the above scenario should be the DEFAULT as I have to beleive that would hold true for most cases.  If doing it differently is actually common enough to NOT do this by default, then make it so that the "default" behavior can be set in the template dwg file along with (most of) the other default settings.  


Then if you need to override the default, so be it.


I'm still trying to figure out your end game here. What does this idea accomplish, besides things looking better when you look at a structure properties inside the program?

Does it improve something important, such as:

  • Pipe flow direction labels
  • Pipe invert labels
  • Structure invert labels
  • Tables
  • Data bands
  • ...?

If not, what is the point?


When I first started using pipe networks, I annotated my network.  The structures had labels indicating In & Out information that just didn't make sense the highest invert was listed as OUT.  I thought it was a major bug -- water doesn't go uphill!  🙂


At that time, I had NO IDEA that I had to manually tell it which pipe to use for it's "Out" connection.  I eventually found something somewhere (it's been so long that I don't remember where) telling me about manually setting this.


But if the structure were to look at the connected pipes and by default mark the LOWEST invert as the "Out", that would make a lot more sense.


After reading the comments here, I can see that there is a need to let a structure label a higher invert as out and/or multiple outs -- but I truly believe that such cases would be less common than having the lowest invert as the out.  Since it HAS to default to SOMETHING, I'm just saying that it should default to the most common method.  And again, they could make this configurable in the template so that if one office routinely has their structures with OUT INVERTS that are higher than other inverts, they could make THAT the default.


P.S. Yes I'm talking about labeling the pipe inverts and flow directions.


OK, you're making sense to me now.

I've never labelled an invert as IN or OUT, but if that's what you're trying to do then this default method is a good idea.


The standard practice at every job I've ever held in this field was to label (in some way or another) each connection at every structure. 


On one job, each pipe was labled as N, S, E or W (and even a SE or similar occassionally). 


At another job, they liked to point a leader at the end of each pipe and say a, b, c etc then there was leader that said something like the following



Inv (a):

Inv (b):

Inv (c):


I even had one job where it depended upon the assigned engineer's preference (one of the two above or the In/Out labels).


At my current job, it's simply in or out.  I hated doing the abc labels -- very tedious.



This kind of goes along the lines of how the hydraflow apps are built with a standard case in mind as opposed to the 100 variable options SSA provides. 🙂 Good thoughts from everyone for sure.


Why not just change the flow meathod to all of your pipes to "by slope".  In most cases this could solve your problem.


The problem is that flow direction is linked to draw direction by default and it can't be changed. 


The user must select by Slope or use the Change Flow Direction command to correct a run.  Both are annoying.



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