In this video, I diagnose and bypass a plumbing leak on the hot water side under my concrete slab. We cap off the leaking pipe and run PEX through the attic.

Sta-Brite #8 Solder + Flux - https://amzn.to/2NRfnOd (this is excessive for a simple plumbing repair, but it is really good stuff and all I use)
Shark-Bite 1/2" Red PEX Pipe (300'): https://amzn.to/2P9DqZg (the length you need may vary)
Mapp gas torch kit: https://amzn.to/3d9GY5M
PEX crimping tool + rings: https://amzn.to/3sqd0Bc