I carry a backpack with me when I leave for the day. My dog who is housebroken and will not go in the house unless I don’t let him out, pissed on my backpack the other day. He managed not to get any on the carpet below. So I washed the thing. like 5 days later he pissed on it again, once again managing not to get a drop on the carpet. What is going on? Is he doing this because he is upset that I have to leave him to go to work?
He’s trying to drench the bomb hidden in the lining?
I tell you Bryan I almost ruptured with laughter at your response…You should go into comedy.
This is only speculation, so it’s probably not really appropriate for GQ, but it’s entirely possible that your hypothesis that he’s pissed (so to speak) about being abandoned.
I had a friend who travelled frequently. She had to keep a close eye on her bags as they were being packed, as her other wise well behaved cat would baptise them if he had a chance.
I don’t get it.
Anyway, there’s a decent chance he’s just “claiming” your by marking his territory. He doesn’t want other dogs to steal you when you’re out and about.
So why did my house broken dog piss on a case of Coke almost as soon as I set them on the floor?
In that case should I piss on HIM before letting him out? 
Sounds like it’s HIS backpack now.
Prefers Pepsi?
And the Cola Wars are resurrected.
With the stakes much MUCH higher.
Back in my skydiving days there used to be a stray mongrel that hung around the drop zone who would piss on parachutes any chance he got.
There was some discussion about having him lay base for a four-man star, but, evidently, he wasn’t willing to get into the jump plane.