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For the first part of this page, we will consider only the cases where the flow directions are wither either of the first 2 options in the list above (upstream or downstream) and towards the end we will consider what happens if either or both of these values is unknown or not defined.
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What does this mean? It means the water flows from A → B, it’s very simple.
So, what happens if we flip the flow direction over to the other way around? In this case, the flow direction actually stays the same and does not change, and what happens in reality is the manholes swap positions, because the flow direction defines which is the upstream manhole and which is the downstream manhole, so after switching the flow direction, we now have B → A, not A ← B.
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Note - this is not the same as swapping the inspection direction. This is a different concept and does not affect the flow direction at all , but requires that the observations in the inspection are flipped around so that they start from the other end of the pipe (in terms of geometry), and any start/end manhole references in the observation codes should also be flipped at the same time. |
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Of course, most standards include an ‘unknown’ value option for both the flow direction and the inspection direction, and in the data, there could be situations where the definition simply does not exist. Both of these situations will give the same results if they exist in the data.
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