When I see traps like that I tend to blame the roofer ..... last year I caught one in the act of removing the trap from a rtu drain as he was also on site because of a water leak. Said "I'm just helping you out because someone installed the drain wrong"
I used to PM McDonald's cooking & refrigeration equipment. As a favor to them, I'd also remove & flush their RTU traps because they'd often grow a blockage.
I never understood why their maintenance guys saw some reason to go and plumb all their three or four RTU condensate drains together, then run it all through a common PVC pipe to the edge of their flat roof.
Are they afraid to get their roof wet?
"You never know what others don't know."
"Ma'am, watch that for me while I go turn on the breaker and SCREAM for me if it sparks or pops...."
I often see that too where they go through a lot of trouble and pvc material of piping an elaborate draining system on the roof to expel the water into a rain drain or close to it. I often scratch my head of what's the point?