As described here (http://www.avsforum.com/avs-vb/showthread.php?t=782601) I am converting a detached garage into my home theater.

There is some power and phone cabling running from the main house to the garage -- which is strung from the roof of the house to the roof of the garage.

Not only is the wire really old, it's running right through some trees, and probably cannot handle the additional amperage it will need to carry.

So we're going to run new wire. And it's going to be in a buried conduit.

In addition power, however, we need to run two RG6, at least two CAT6, one phone, and probably a component video+audio and/or hdmi cabling between the house and the garage/theater -- again in buried conduit.

I know we cannot run the power and the a/v and computer cabling all in one conduit.

The question is: How far apart do the buried conduits need to be? I'm planning to only dig one trench. And how deep should they be? I'm thinking 4 feet?

Well, if you are running any low voltage cabling next the High voltage the minimum requirement is to be at least 12 inches away, and if you have to cross high voltage lines do it at a 90 degree angle so there is as little interference as possible.

It it were me I would put as much room between the power line as possible. Since it seems like the run could be quite long you will need that low voltage signal to be as clean and noise free as possible when it gets to the receiver. Go for about 24 inches you can't ever be too sure.

Makes sense. Maybe I bite the bullet and run two trenches, separated by a few feet. Luckily the critical viewing all takes place out in the garage theater. It's just casual viewing signals that will have to pass along the buried conduit and into the house.