I have a 50 amp 240v 4wire hot tub that I need help with. (1) Can I run 6/3 romex from the main panel in the garage, down to the basement, thru the basement to a Junction box, then out of the JB thru the basement wall with pvc 30' to a disconnect at hot tub. (2) Drive a ground rod at the tub with #6 ground wire. (3) Where the wiring passes from the garage wall to the basement it will be below 18" but it will be in a drywall wall is that ok. (5) I have been told that if the tub is setting on a concrete slab with no steel in it it must have a rubber mat under it if so who sell this mat.
You can use the Romex inside the house. That part is OK.
Legally the ground rod has no significance. It might help establish your ground plane in a practical sense but the code is silent on it. If I was doing that I would add a #8 ring around the pad. I am not sure about the rubber mat thing. That may be a local accommodation but I am not sure where they justify it in the code. I have seen 3 foot or wider decks around a spa going for the same thing and that sounds better to me. A wet rubber mat sitting on an energized concrete pad would be energized. You need to get a ruling from your AHJ on this part. I am not sure what a totally legal solution would be without chipping concrete. (Maybe saw cut a groove around the spa, push in a #8 and pack it with grout?)
Bonding conductors are not #10, they have to be #8 solid copper.
Lite bulb: I can give you the NJ take on the non-conductive mat part. Yes, per our DCA it is compliant in lieu of a ground ring for a hot tub on an existing slab.
Items are available at the 'spa stores' and they make a killing on that item here.
Most ECs will either rent a concrete saw, or 'sub' it out and do what Greg said. Sawcut +/- 2" deep, install solid, bare #8 Cu, get it inspected and grout it closed. A tail is put into the tub box & tied to the mfg bonding within.
I've seen switchboard mats, cheap vinyl runners used by homeowners who like red tags. There was debate on 'Trex', but last I heard, DCA said....'no'.
As to pinning it on a code article, it is mentioned within the UCC (NJ 5:23-6) or somewhere within a Bulletin.
(C) Interior Wiring to Outdoor Installations. In the interior of a one-family dwelling or in the interior of another building or structure associated with a one-family dwelling, any of the wiring methods recognized in Chapter 3 of this Code that contain a copper equipment grounding conductor that is insulated or enclosed within the outer sheath of the wiring method and not smaller than 12 AWG shall be permitted to be used for the connection to motor, heating, and control loads that are part of a self-contained spa or hot tub or a packaged spa or hot tub equipment assembly. Wiring to an underwater luminaire shall comply with 680.23 or 680.33.
Clearing what Greg said above. Amazing how many words it takes the code to say what he said.