Haven’t seen this one before (in attic space obviously - directly into vent stack)
SWEET!!:shock:
wrong in so many ways
irc p2803.6.1
I wonder how Mr. Murphy will be involved when the valve releases super heated steam into the system and it discharges out every fixture drain while the kids are brushing their teeth?
And that very well may happen - it’s a 1993 unit :shock:
That’s a new one on me. Curious is that CPVC vent?
Since the valve opens below boiling point, I don’t think that’s going to be an issue. It’s whole purpose is to prevent superheating. Of course the valve might have been discharging for years and who would ever know?
PVC schedule 40 is only rated for 180 degrees???
Yes, correct, and 1) I did mention Mr. Murphy, and we all know he doesn’t play by the rules, and 2) you are also assuming a maintained and fully operational valve. A valve manufactured to open at 210 degrees, and a 10 year old worn valve opening at 212+ degrees is a HUGE difference. And 3) did I mention Mr. Murphy? 
If the valve fails to open when it should, fear of the discharge is a distant second to fear of the vessel rupturing and suddenly expanding at a 1,700:1 ratio. With a failed valve and superheated water, the vessel becomes the hazard much more than the discharge. The excitement begins when someone flushes a toilet or opens a faucet and pressure drops allowing water to immediately flash to steam.