The inspector says that the waste vent shown here has to be dropped to a minimum of 12" from the roof. How do I do this?

The inspector says that the waste vent shown here has to be dropped to a minimum of 12" from the roof. How do I do this?

If it's a vent terminating through the roof, are you sure he didn't say it needs to extend a minimum of 12" ABOVE the ROOFTOP?

The vent is already over 12" above the rooftop. I think the inspector meant the 4" has to extend 12" below the roof before converting to 1-1/2".

It's tricky because there's less than 12" between the roof planks and the top plate. Which means if the 4" comes down 12", the wall will bulge out in that spot. Here's a wider picture.

Do I have to get a new vent or can I use some type of transition to go from what it is to 4"?

I'm confused as to why he wants you to upsize the 2" vent to 4" -- Is this his idea of meeting the cross sectional requirements for a 4" main building drain?

Or are you trying to re-use an existing roof flashing?

Another thing I see that I would call out if I were inspecting this work is the transition from 4" to 2" is incorrect -- Correct me if I'm wrong, but You have what looks like a 4" coupling going through the roof with a 4"x2" flush bushing glued into the bottom of it, a short piece of 2" PVC pipe and then a 2" rubber clamped coupling.

The 4"x2" flush bushing is a definite no-no -- This should be a 4"x2" bell reducer (http://www.amazon.com/gp/product/images/B000H5RTJI/sr=1-104/qid=1177881446/ref=dp_image_text_0/102-0591002-5255361?ie=UTF8&n=228013&s=hi&qid=1177881446&sr=1-104) that tapers into an actual drainage fitting.

And the rubber clamped coupling should be replaced with a CP-200.