kk,

If it was made from PVC pipe I would say it is a bubbler and would be controlled from your controller but it is made out of what looks like a threaded black iron pipe which makes me think it might be a gas line but for what? Some kind of torch or maybe under some kind of BBQ set up. But why so low and close to the house. Could be a vent from your stove. Best Bet, have a plumber check out where it goes up inside the wall and goes into your attic space. Go into the attic and see if you can see a iron line coming from that wall edge across your attic to another wall that may have a valve somewhere. Hope someone can recognize it specifically because I am getting brain damage from guessing. JMHO Aloha