AutoCAD MEP
You can specify the invert elevation by chosing the bottom center elevation on the justification dropdown on the properties palette once you start the pipeadd command. I would recommend going into your piping preferences (_aecbpipingpreferences) and changing your slope format to a rise over run. That way you can change to slope to 1/8 or 1/4 or whatever your prefer. In the chicagoland area, this is the format of the way it is done, although I know other areas use a percentage for the grade such as 1% or 2%. I would also draw using a split screen with one screen in plan view and the other in an isometric view. Please turn on your compass and make use of it. Using the "p" command while running mep objects will allow you to turn your piping in any plane regardless of the current UCS. The "p" command will change the plane of the compass which allows you to route piping in any plane without switching ucs.
When routing sloped piping you are going to need to think about your layout and start from either your highest point or your lowest point and draw from start to finish. It is not a good idea to draw two different areas and then attempt to connect them. It can be done but it is much easier drawing from one start point and then branching off from that location. I also have several different routing preferences set up for my different types of elbows and sanitary tees/combos. It is easier to let the routing preference place the part then going back and manually placing the part. There are several different types of cast iron waste elbows and they are all used depending on the situation. In Chicago we have to follow code and the code says Cast Iron Hub and Spigot piping for all waste. Long Radius elbows on a vertical to a horizontal run and intermidiate elbows on a horizontal to a vertical run. Quarter bends are only to be used for vent lines. They are not allowed for waste. All of these different types of elbows are setup on a different routing preference so when I need to switch elbows I just switch the routing preference.
I would also put all of your fittings on tool palettes so you can grab a fitting when you do need to manually place a fitting. Its faster than searching for a fitting.
In addition, I never stretch sloped piping when moving a run with several branches with several different slope values. Its impossible to get it to stretch in a way that you would expect. Instead I use the move command and use the centerline of a sloped pipe as my base and make my move using the center line of the pipe as my guide. I use the pcon and the pcur snaps all of the time while using sloped pipe. You should add them to your right click snap menu. I am surprised that Autodesk has not already done this for out of the box setup.
Hope this information helps at list a little bit.
What the underlying problem is the fact that the pipe "rotates" when changing elevations or changing direction. This occurs with ductwork, conduit, cabletray, etc. It is a long standing issue with Autocad MEP that they have not "fixed" yet. If you search these same boards you will find numerous posts on the subject. I run into the problem alot with the bottom of duct not actually being the bottom but it is the top. It is very noticable when you are changing the location of a tap. You tell it you want it on the bottom of the duct and it will show up on the top.
Autodesk is well aware of the problem, they just have not yet come up with a solution. I would recommend filling a support case outlining the issue you are having. The more support requests they receive the more likely they are to take a look at solving the problem.
the orientation is due to rotating the vertical pipe to keep the rise drop at 0 deg angle so the bottom of a vertical pipe does not exist and the pipe is rotated to align the rise drop. When drawing horizontal again, the cursor location is dependent on the draw direction, but the pipe is located correctly. if you draw left to right, and off the rise draw up or down, the cursor is located correctly, if you draw in the same direction the cursor is to the top side relative to plan, but the pipe is located correctly.
After the next point selected in plan view the cursor resets to the correct position of bottom center since it now knows the pipes location to plan view.
HTH
Gregg Stanley
Gregg Stanley
QA Analyst
AEC
Autodesk, Inc.
