PEX can’t be straight connected to a water heater. To start with extend a pipe 18 in. from the water heater and link the PEX to the pipe. • The Zurn formulation additives lead to tubing that qualifies for the best chlorine and UV resistance as described in ASTM F876, https://cesarvbhnt.blogars.com/32227551/top-guidelines-of-whole-house-repipe