tankless WH and CPVC

Local AHJ wants 8’+ copper or other material at hot water discharge side of tankless water heater; no CPVC. Anyone know a reason for this? Seems to me there would be no more “shock” fro 120 degree water from a tankless than a regular tank heater…


Code requirement and probably a manufacturer requirement also.

Its a safety backup in the event of multiple failures in the tankless unit. Flow sensing and overtemp sensing would both have to fail to melt a plastic pipe but it “could occur”.

Same idea for the one inch gap for B-vent’s, paper will not ignite when left touching a b-vent even for years. Its a safety requirement for unusual events somewhat like thermal runaway.

Thank you Mr. King. That makes sense. I must say the controls I’ve seen on tankless units look like they were made by NASA engineers though, and I haven’t heard of runaway failures. Interestingly Noritz doesn’t want a T&P valve on the discharge, only a pressure safety valve.