Solar defrosted sewer vent.

When it gets real cold in the dead of winter, it is not uncommon to for rooftop vents to frost over, causing gurgley pipes and sewer smells. We are trying out a trick we just learned...

First cut the top of the vent pipe at a 45 degree angle, with the open part facing south.

Then paint it black.

The frost will have a hard time trying to bridge that longer gap...

...and the sun (that tends to be bright on the coldest days) will heat up the pipe and melt any frost away.