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I'm planning to re-design my yard, and I'm looking to decouple the dependencies between contractors.

I am planning to add some outdoor appliances (e.g. hot tub, sauna) which would require adding new wiring from the panel to the appliances. At the same time, I want to change the grading of the soil and re-do the walk paths and surfaces where the appliances would rest. Lastly, I want to integrate a rainwater collection system which would require re-doing the sprinkler plumbing. As far as I can tell, this would introduce a dependency between the electrician, landscaper, and plumber which I want to contract separately.

One idea that I have to remove this dependency is to have the new water and electrical lines be in a conduit that is accessible from the surface. Here is a model of what I am imagining:

Low fidelity model of a utility trench at surface level

It is meant to be a trench at the surface level of the ground. It would house water and electrical lines that end up at outdoor spigots or outlets. The trench would have a removable top cover for ease of maintenance of the utility lines.

Then, I could just tell the landscapers to build the conduit, and I can have the electrician and plumber come in at a later time. In theory at least.

My questions to the community:

  • Does this plan make sense? Or would the electrician and plumber have qualms about filling in the trench after the landscapers are done?
  • What are the relevant code requirements in the United States for plumbing and electrical surface-level conduits like shown above?
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  • Check with your local building department. Code requirements vary by location.
    – JACK
    Sep 21, 2023 at 1:53
  • do the conduits before landscaping
    – Traveler
    Sep 21, 2023 at 2:40
  • It will work but will be more expensive. Also water and electric cables are meant to be at different depths, around here anyway. I would trench it to the deeper level required. Get the plumber to put in the electrical conduit with a draw wire. The electrician can then pull his cables through later. Sep 21, 2023 at 3:21
  • Yes. Electrical conduits must be at a certain depth (18" of cover) post-landscaping, i.e. the landscaping isn't allowed to run them shallow. And water pipes need to be at a certain depth. Climate change doesn't care what your historic freeze risk or freeze depth was. Sep 21, 2023 at 18:57

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Most jurisdictions don't allow conduit to be installed by contractors not licensed as Electrical Contractors. I do not know code requirements for plumbing, the NEC does not prohibit electrical and plumbing in the same trench.

Conduit is either above grade or below. Above grade the NEC requires:

352.30 Securing and Supporting. PVC conduit shall be installed as a complete system as provided in 300.18 and shall be fastened so that movement from thermal expansion or contraction is permitted. PVC conduit shall be securely fastened and supported in accordance with 352.30(A) and (B).

(A)Securely Fastened. PVC conduit shall be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, conduit body, or other conduit termination. Conduit listed for securing at other than 900 mm (3 ft) shall be permit‐ ted to be installed in accordance with the listing.

(B)Supports. PVC conduit shall be supported as required in Table 352.30. Conduit listed for support at spacings other than as shown in Table 352.30 shall be permitted to be installed in accordance with the listing. Horizontal runs of PVC conduit supported by openings through framing members at intervals not exceeding those in Table 352.30 and securely fastened within 900 mm (3 ft) of termination points shall be permitted.

Below grade the NEC requires:

352.10(H) Underground Installations. For underground installations, PVC shall be permitted for direct burial and underground encased in concrete. See 300.5 and 305.15. enter image description here

(Section 305 applies to 1000+ volts.)

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