For this series of articles, the Routed System of choice will be your average everyday home plumbing. The DWV (drain, waste, and vent) system to be exact.
The DWV layout I am using as an example is for is for a little eco cottage design that has all of the mechanicals running through chases and partition walls to keep the thermal envelope as intact as possible — but the technique will work on any design equally well. Also of note is that the design has a FPSF (frost Protected Shallow Foundation) slab……which means there is only one chance to get things right.
The penetration drawing is a plan view sketch that shows where the various pipes pass through the structure at whatever level is represented. It is created as the first sketch in a part file located in the overall plumbing assembly. This is a hold-over from ship design days, but it works on houses as well.
For this particular house, you can see that the stack and vents run up a 2” x 6” partition wall. There is a wet vent at the other end of the wall as well, but is not shown. All of these penetrations run down the center of the wall, and can be drawn on the same plane, which is where I started.
To begin the first sketch, I created a plane on the centerpoint of the stack circle parallel to the partition wall (XZ Origin Plane) that it is located within, then created a sketch on same.
On the new sketch I projected the center point of that same stack circle, then created a vertical line nearby, which I then constrained to it.
When doing so, I made sure not to constrain the center of the line (the program usually wants to do it this way) to the projected point as the top portion of the line needs to be fixed, and the bottom I will need to be able to tweak later. The result should be a vertical line connected to the center of the stack circle, which can be dragged up and down as you please without the line resizing. If it did resize, it would mean that it was constrained to the center or one of the ends. It was then dimensioned in both directions as shown…
This line will align the stack pipe when it is placed.
The next line will align the main sewage line, and will include the ¼” per foot (I use 1.2°) pitch needed for proper drainage. I created this line starting at the bottom of the stack line just created, and angled it a tad downwards as I moved a tad leftwards (while drawing this line I held down the Ctrl key to stop Inventor from inferring a constraint).
I then projected one of the lines in the wall, turned it into a construction line, created a Pitch parameter of 1.2°, and added the new parameter between the two…
I started with a 4” long sweep elbow (all fittings are Spears), and constrained the axis of one of its legs to the stack rise line…
As you can see in the image below, the circles in the layout are all sized to the outer socket dimension of the pipe called for. This is a must if you want things to fit…
I use standard Inventor Content center pipe as seen below. The length is irrelevant at this point.
In the real world, the 1.2° pitch in the pipe is achieved cocking the pipes in the sockets a tad, so the placement of this first pipe section will need to mimic that. After the pipe selected above was placed into the assembly, it was first constrained by its axis to the pitched main sewage line created earlier…
Now for the ‘Swivel Joint’ constraint that will allow for the pitch. To create it, I fired up the Constraint tool and select the centerpoint of the shoulder ring at the bottom of the fixture’s socket…
…and the same thing on the end of the pipe…
…and there you have it. A properly pitched pipe. The elbow slid down to meet the pipe, and the whole thing can, and will, be adjusted in unison later.
I now right click on the pipe and select Copy, then Paste a new version into the assembly…
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