It seems to be that the Snap A/V wire that I’ve used for speaker wiring, maybe 20 years now, was rated or called direct burial wire. I don’t think it uses that designation nowadays.

In any case, it is obviously sheathed cable that one would consider to be waterproof. And there have been no failures in any cables I ran in the ground going back 20 or 25 years.

What are your thoughts on standard cables run in the ground, whether direct burial or not? We don’t get frozen ground in the winter here in California, so no issues there. Once sunk in the ground, never disturbed.

Appreciate your thoughts.

Any jacket on any cable can get wet and it's not going to hurt anything.

It's a different story however when that cable jacket is 'immersed' in moisture 24/7 365. Water will slowly penetrate that jacket over time and eventually get to the copper. Very obvious when you take a piece of wire that has been sitting in water for years, cut it in half and strip it back - you see the corrosion on the conductors (and wicking was not the cause).

Polyethylene (and a few other types) are what you'll typically find direct burial cable jackets made from. They completely block water intrusion and don't break down over time (at least not in 50+ years). They also tend to be sunlight resistant (UV resistant to be exact).
These cables cost a little more because of the materials used.

I wouldn't use cable that's not designated as 'direct Burial'. I don't think it's worth the problems if it goes bad.

Even in conduit, I use DB cable in case of a leak.

"Never disturbed" in California, land of earthquakes?

When I worked for a CI contractor, they only used Liberty DB cable for outdoors- good cable, but if the jacket was nicked, bending it resulted in the jacket breaking open and exposing the insulated wires.

i don’t sell any products that last half that 50 year span. Maybe it’s ok to sell a system that won’t go past 25 years (or might - 15 inches of rain a year and no freezing).

Ironically, the only inground cable that has failed in my experience was a direct burial cat6 that would no longer send HdBaseT from a house location to the patio.

In conduit?

Direct burial has nothing to do with freezing conditions.

Water infiltration like Brad mentioned is the number 1 issue, and when encased by soil that is holding that moisture or a conduit that is guaranteed to have water sitting in it there is degradation to the outer jacket. The issue that Brad didn't mention is pests. A lot of DB cabling now also has something in the outer jacket to help prevent pests from chewing through it (assuming you are not using a conduit system). I have seen ants destroy an electrical cable in a house causing circuits to stop working, trying to find that in a buried cable would be impossible.

No idea, I didn't run it.