As a disclaimer, I'm aware that this is technically supposed to be done by a licensed electrician. If it's possible to do this project myself, I'm willing to accept the risks in order to save money.

I have a newly constructed house, located in California, with a back yard with no landscaping yet. I'm planning to put a hot tub in the middle of the back yard and then dig a pond around it and put a bridge leading to the hot tub. Here's a picture of what I have in mind:

Backyard Plan

This is a 220 volt installation. What is the best conduit and copper wire to run from the main panel to the 50A GFCI sub panel?

It seems that the cable from the GFCI panel to the hot tub would need to run underground until i reached the bridge, then underneath the bridge, then underground until it is near the hole in the hot tub where the wiring connects, then over ground into that hole to power the tub. Since it's going both over and underground several times, it seems that liquid-tight flexible metallic conduit could work for me.

I've taken a look at the electrical codes related to this and I've read that the copper inside of the flexible conduit that will be partially buried going to the tub should be 6 gauge and individually insulated (not sheathed), and there should be 4 color-coded wires total: (1) red & (1) black hot, (1) white neutral, and (1) green (insulated) ground wire.

Any help would be greatly appreciated.

  • CA law doesn't require an electrician. Permits, yes, inspections yes). DIY is ok, just don't be a jackass. Nov 8, 2018 at 20:41
  • 1
    Liquid-tight conduit is unnecessary. Any underground cable is assumed to be in a wet location, no matter if it's in a conduit of some kind or not.
    – brhans
    Nov 8, 2018 at 20:45
  • ... doesn't require an electrician if the work is done by the homeowner. The implication is that you won't risk your life or that of your family by doing shoddy work.
    – isherwood
    Nov 8, 2018 at 20:50
  • Yes, the defense is in the insulation of the wires, not the conduit. All conduit is presumed to be 100% underwater 100% of the time, even liquidtight. UF cable and THWN-2 wire are built for that. Nov 8, 2018 at 20:54
  • Thanks for this. It saves me a bunch of money to not buy the liquid-tight conduit. I'm still unsure which conduit and wire to use between the two electrical panels.
    – Dewayne
    Nov 8, 2018 at 20:59

1 Answer 1


From the main panel to the subpanel, you'd want to run either #6 copper UF cable.... Or if in conduit THWN-2 wire, either #6 copper or #4 aluminum. Aluminum is fine for a feeder like this.

From the subpanel to the hot tub, any conduit will do, because all cabling must be wet location rated, and conduit is presumed to be 100% full of water anyway. My first choice, if you can bear the pipefitting required, would be Rigid or Intermediate Metal Conduit, which only requires a 6" burial depth and lets you use conduit for ground, saving a wire. I would not use EMT because it would rust quickly. I would not use Schedule 40 PVC, but would use Schedule 80 PVC.

Inside the conduit I would only use THWN-2 and only copper, since it is outdoors and genuinely at risk for water exposure.

You don't need to worry excessively about shock hazard past the GFCI hot tub panel, stopping shocks is its job.

However California has seen at least one monstrous wildfire started from arcing in a bad hot tub connection, so AFCI protection is warranted if you are in a wildfire area.

  • One problem -- there is no such thing as a 50A AFCI. Nov 10, 2018 at 2:05

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