Small back story: This is a Philly row home, so the long walls are solid brick. original outlets were non-existant or embedded in baseboards. While most of the home is being wired with romex, I am chiseling out boxes and conduit paths for switches and boxes which need to be in these walls. I have much less experience with conduit.
One of these is a three gang box, with 1 1/2" piece of conduit extending through the floor to the basement and a second to interstitial space between floors. My concern is not overloading the conduit. My supplier couldn't get three gangs with 3/4" so it was the best I could do.
The three circuits are two lights and a 3-way switch. They are on the same leg coming from the floor. So far I have been running grounds in the conduit. I'm pretty sure I do not have to but I was just being cautious. With this setup, I would have 10 wires (14 ga) going through a piece of 1/2 If I didn't omit the grounding wires.
What is the best way to do this? Can I just bond everything to the boxes in the floor and ceiling and omit the grounds?
*** UPDATE *** I thought that this was relevant, despite being an issue possibly local to Philly. Luckily the inspector did not see the wiring in question as it would have been much harder to fix. He did however, see a steel conduit run in the basement for the hot water heater and furnace (two circuits). He informed me that in addition to the pigtail, I have to run a ground to the box. He insisted that all Philly inspectors enforce this. He also said it doesn't matter where or why it's in conduit; if it is, it requires both a pigtail and a home-run ground. I asked two professional electricians in Philly and they confirmed that this is dumb but enforced.