Stage one, mounting of 2 Navien HE Water Heaters in a cascade system for residential use.
Job complete and ready to bring the hot water system online.
Zereski Plumbing & Heating  Helpful Tips, Links & Pictures.
zereskiplumbing@gmail.com  508 843 3656
This picture shows a screw through a pipe in a customers house.  It came from their cabinets, apparently the installer didn't use a stud finder.  We found this using our drain camera after several other companies were unable to locate the resulting leak from the screw which showed up in the basement running down the foundation wall.
We pulled this rock out of a drainage system that was backing up during final testing phase of a new home.  Seriously...who flushes rocks down a toilet?!?!??   
So you want to be a plumber aye?  Hope you have a weak nose and a strong back.  Claustrophobics need not apply. 
This image shows water pouring over the roof during a wet test (filling the entire drainage system with water and checking for leaks) on a new construction home.  Not only does this test the drainage piping, but also the roof penetration seal as the water pours over the roof pipe seal.