A garden house is, maybe 0.5" inside diameter. 

Looking at a prospective buy and hold property and noticed 3 large tree branches (~1-2ft diameter) that hover about 3-5ft above the neighbor's roof. 

Provide an area floor drain near the WD and water proof membranes in all wet spaces.The toilets waste should be a 4" diameter, so you can save a few bucks here and there.

This is a piece of double-walled sheet metal pipe that is fairly large outside diameter, like 8" or so. 

These trees are massive: 60-80 ft tall, trunks 5 feet in diameter, branches the size of trees.

I also enjoyed it when I found an  old Blaze line  it harkens back the day of rip saws 30 feet long and loggers standing on platforms 20 feet up from the ground cutting down a tree that is 20 foot in diameter and 200 feet tall.. :)  then hauling them to a river or in those days they built little railroads all through the mountains to haul out the logs.. those old right ways are still all over the place in the northwest LONG abandoned but still there in the deeds.. .  

The pipe from the house to the septic is cast iron and over time the diameter of the pipe shrunk. 

The HVAC person did mention about high pressure, and that was the reason to replace a larger diameter line.

When going taller than 10' on the front wall it is without question going to require a wider footer, typically larger diameter rebar, the block wall will require vertical and horizontal rebar as well with the concrete pour.

The coupling looks OK, assuming that it's designed for the outside diameters of the pipes, but the notch in the joist is bad.