Hello all. Thanks for everyone’s help. Got a new check valve installed thanks to y’all’s expertise. Good news is the plumbing held after the install and elsewhere since the freeze in TX. Bad news is I saw a leak while testing and realized this bad boy corroded away and finally snapped. Looks like a second relief valve for the heater (Pentair MasterTemp 400). Is this even needed? If not any suggestions on what to plug with? If it is needed are these just Home Depot style plumbing parts? Thanks for the input. Ready to put this storm behind us.