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  1. Most sprinkler systems directly bury the wire next to the water line. So, this is a big upgrade from that. The main purpose is to protect the wire from being cut if someone digs there.

  2. Why not use 1/2" pcv conduit? b/c it is double the price and the total distance I'm going to is ~600'. So, the cost is significant. PVC conduit is massively overkill as the wire is carrying low voltage and low current.

  3. The voltage is 24 VAC and current is 350 mA. (.35A). The wires are switched by a computer for ~ 10 min on time duration per day. And the supply current will be limited by a 1/2 A fuse. The conductor ampacity is 13A.

The code is sort of ambiguous on sprinkler wiring. I am a Professional Engineer (Electrical), and my site is a rural ranch.

So, interested to hear any viewpoints.

Thanks in advance.

Edit:

In response the thoughtful answer about using some to mark to know where to dig, I place several inches of sand around all buried pipes. The soil here is a rocky, aggressively expansive clay and the sand allows ground shifts to avoid breaking the line as well as serving as a marker, so you know when you're close.

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    Welcome. You haven't really asked a question here. We're not a discussion forum. Please see How to Ask and take the tour.
    – isherwood
    Sep 19, 2022 at 14:00
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    @isherwood Good morning! I have to disagree with your vote to close. While it's not a "how do I do this" question, it's clearly asking for advice before proceeding, thereby avoiding the XY situation. Once the OP decides on an approach, we can help him with the "how to do this" part. ...just my opinion, have a GREAT DAY!
    – George Anderson
    Sep 19, 2022 at 14:27
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    There's no question up there other than "why shouldn't I do this?" That's both vague and a matter of opinion.
    – isherwood
    Sep 19, 2022 at 14:29

4 Answers 4

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There are no code requirements that I know of regarding burying low voltage (IE sprinkler and LV outdoor lighting). PVC conduit is ridiculously expensive right now. Because there are no code requirements, you could protect it in any way you see fit. When I've installed sprinkler systems, I ran the valve control cables underneath the pipes going to the valves to protect the cable. But you could use PVC conduit (expensive), PVC water pipe, funny pipe (yes that's a real term) or just about anything.

It's a good idea to protect it, fixing a break is a PITA.

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    Depending on the depth and concern about accidentally severing either the water or control lines with digging, it might be beneficial to bury some marking tape a few inches above your pipe run, so if someone digs in the future, they'll hit the marking tape first, before going deep enough to hit your lines.
    – Milwrdfan
    Sep 19, 2022 at 14:36
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Cost and effort, like you said.

Done. Totally valid.

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It's a good idea up to about 25 feet.

For 600 feet to save cost I would prioritize. Do it only where the wire is most exposed to damage: parts that are above ground, shallow, near flower beds or anything likely to be dug up by occupants, and a few feet either side of any termination, junction box, valve box, etc.

Elsewhere, if you're just crossing expanses of lawn, I'd bury the raw wire deep enough to avoid typical yard work eg aerators and dethatchers. If you want to be fancy you could add a 3 foot loop in a splice box every 50 feet to allow for easy diagnosis and repair of problems. That would be easier and cheaper than piping the entire 600 feet.

In addition to the cost/effort I'd experiment with the pulling capability of my wire before buying and laying all the pipe. If it's not designed for pulling it may snag and break with just so much as a single 45 degree bend. If you can't pull new wire through your COMPLETED BURIED conduit without breaking it .... it's a bad idea.

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    sorry the HV run is only 300' (power pole in middle) and I always plan for more than i intend to use. I never base anything on intended use: that always turns out to be inadequate. Paid and pulled. Yes, I know the rule about sharing with the 2, although not all the rules are based on logic. Code is written by politicians, unions, and manufacturers among other ligit sources such as IEEE committees which have their own agendas such as taxing, making more work, or additional product sales (yes, it's corrupt - but I digress). The scope of this has exceeded the original intent, but interesting.
    – ramblin_wreck1
    Sep 19, 2022 at 17:08
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    on the ethernet this will be a switch at the power pole (300' mark) that will act as both a repeater and a port for a diagnostic computer. So, it is not twice the distance. I may go back and yank the cat5's out and put them in another pipe. I started this a low budget project but is becoming expensive. If I had to have it done by someone it would probably be in excess of 60k. It now involves 2 storage tanks, 2 pumps, 2 buildings, 8 sprinkler heads 10 SV valves 3 PLC's, a dual gate, HD POE cams and a more in the future - It was going to be a collection of small systems, now a large integrated 1
    – ramblin_wreck1
    Sep 19, 2022 at 17:19
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    @ jay got that; early on I said this was rural ranch which is more like industrial.... Suffice to say ...original question was answered - thank you all
    – ramblin_wreck1
    Sep 19, 2022 at 17:23
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    @jay613 ramblin says they're an EE, and seem experienced with industrial control systems. It's no wonder this system seems like an industrial one, because it is designed like one.
    – jaskij
    Sep 19, 2022 at 18:21
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    @jaskij and manassehkatz thanks, I have been convinced to make that change - it was penny wise/pound foolish; To keep the HV/LV all separate, I guess it's going to mean a separate hole in the bottom of my Hoffman box as well
    – ramblin_wreck1
    Sep 19, 2022 at 18:53
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the trench is already there and shared with another 3/4" PVC electrical conduit containing 2 #8's

Clearly you can't put the LV in with the existing cables, but there's nothing stopping you from strapping the LV cable to the outside of the existing conduit.

There's certainly less protection this way, but more than having the LV cable direct-buried. A zip-tie every metre should be sufficient to stop them separating and drifting.

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    Per above, I had already decided to remove the 2 cat5e's and run them in another tube
    – ramblin_wreck1
    Sep 20, 2022 at 17:17

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