Re-routing discharge pipe from hot water heater's T&P relief valve

Question

Our new construction home (completed build in August 2018) in northwest Georgia (about 40 miles NW from Atlanta) has an electric water heater installed in an alcove in the corner of the garage.
The current discharge pipe setup from the T&P relief valve seems incorrect and self-defeating and maybe even dangerous, depending on what sort of discharge event happens (if one were to occur):

1. The discharge pipe runs up vertically (into the ceiling, then over and across the garage, down into an exterior wall, where it finally terminates outside)
2. Before encountering the upwards path, there is a tee, where the other path (downward) terminates into a ball valve, to allow for drainage (according to the builder)
3. There are several 90° elbows, which, from my limited understanding, can potentially restrict discharge

Current setup:

"Snapshot" of what the beginning portion of the pipe looks like behind the drywall (the red PEX pipe):

What I'm contemplating doing is:

1. Remove most of the current setup (capping off the now-useless pipe, extending from the ceiling)
2. Re-orient the T&P valve such that it points towards the front of the water heater
3. Run a new length of (probably copper?) pipe that extends from the T&P valve towards the front of the water heater, then down the front, and finally terminating near the floor.

Idea for new pipe run:

There is no floor drain in the garage, so I am not sure if terminating the pipe into the garage is a viable (and safe) option?
Or, should I just leave this as-is?

The garage (and home) is on/part of a monolithic concrete slab, so there is no worry about flooding/damaging a basement.
The garage floor is "recessed" such that the interior walls of the house sit about ~2 inches higher than the garage floor, so unless there'a catastrophic event where water is being released non-stop for hours before being noticed, it might be OK?

Example of "recessed" floor:

Answer 1

Draining up does not work

The T&P valve drain pipe is no different than any other drain, in that it relies on gravity to function at the end of the day. As a result, your builder's completely bizarre installation needs to be removed and redone, as you show in your pictures, as it violates several of the operative points in IRC P2804.6.1, including points 9:

9. Be installed to flow by gravity.

and 12:

12. Not have valves or tee fittings

PEX is listed in IRC Table P2906.5 as an allowable material for water service, though, so Point 13 permits its use for T&P relief valve piping.

Your plan might work; you may need a pump, though

Your plan may or may not be acceptable, it depends on how the AHJ interprets IRC P2804.6.1 point 6 in your (admittedly odd) case, though:

6. Discharge in a manner that does not cause personal injury or structural damage

If draining, via the obligatory airgap of between twice the pipe diameter and 6", to a floor that is not further drained is not acceptable, what you can do is use a basin and float-operated pump setup so that any drainage can be pumped to a place that doesn't risk damaging the house. (They make all-in-one kits of this nature for draining things like washers.)