Yea well I been in many houses with T and p not hooked up to anything at all some in the the hallway closet . Great Ideas Mark the solenoid valve at W/H in the pan if there is a pan? Doesn't help if you've got a tand p legally dumping on the floor because to dump it in a pan is illegal but in such a case inspector may allow a pan under the heater that's capped off but has a sensor in it .
Reach 4 a t and p must not discharge less than 6 inches above floor that's the minimum and 2 foot max just one of our differences in code
UPC Section 608.5 gives those numbers for outdoor discharge. I don't know what they would apply for discharge onto the floor.
IPC 504.6 Requirements for discharge piping. says
5.Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor or to the outdoors.
12. Terminate not more than 6 inches (152 mm) above and not less than two times the discharge pipe diameter above the floor or flood level rim of the waste receptor.
So yes, quite different. Georgia has a cool IPC amendment, allowing discharge uphill with a special configuration.
https://terrylove.com/forums/index....and-amendments-to-the-georgia-ipc-code.89929/ This would be especially nice for water heaters in basements.
For cold places, I would like to see discharge outdoors but with a relief method to feed indoors if the outdoor path got blocked. If the dry outdoor path suddenly had hot discharge, that is not going to freeze up.