EBC: Plumbing, Electrical & Mechanical Rough-In

Drain Waste Vent (DWV)

The drain, waste vent system is pretty simple. The half bath will have a composting toilet so I put in a drain pipe for the urine diverter. There’s also a 2 inch PVC pipe that runs up through the stud bay and out near the top of the wall for the composting toilet compartment exhaust system. I’ll mount a muffin fan on the exterior of the cottage. This will create a negative pressure area within the compartment.

I don’t want to have any penetrations in the roof so I’ll run the vent stack through the wall and then up through the berm. I’m considering not installing a vent stack at all and just use air admittance valves instead even though that isn’t code.

In the kitchen I have a drain pipe for the sink running through the wall. There’s also a ½ black iron pipe gas line for the range. The propane tank will be located on the back side of the cottage.

Water Supply

We’ll have hot and cold water lines running to the sinks in the kitchen and the half bath. I’m using 1/2” PEX for both. To limit penetrations in the berm wall, especially low ones I opted to run the supply lines for the kitchen along one of the beams.

I ran the water line through the double front wall. There is a 1 1/2” gap between the two walls which make it significantly easier than drilling holes through each stud.

Back when I had the trench open for the waste line for the cabin septic system I dropped in a run of 3/4” PEX and 1” electrical conduit to supply the cottage with power and water. This is where the supply lines from the kitchen and the half bath meet. Later I’ll install tees and tie the cold water lines into the 3/4” line from the cabin. I’m considering installing a wood fired water heater for the cottage. More details on that in a post.


Electrical was by far the most complicated part of the rough in. I used direct bury Underground Feeder or UF cable for all my runs in the wall as the sheathing is more durable than Romex and it will be subjected to the stress of the cob and light clay straw install. I used 12 gauge wire for all my main runs and then 14 gauge from switches to lights and fans.

Running the circuit for the air conditioner through the ceiling