The wire in conduit will be cheaper and safer. Pvc is cheaper and will not corrode. Bury it at least 18 inches to the top of the pipe. You may also want to bury some caution tape about midway between pipe and the surface to alert anyone digging of danger below. Pvc should be bent in gradual sweeps, when using 90 degree prebent pieces it is best to use pvc coated rigid. This will prevent the possibility of the pull rope from cutting into the 90. Always Check Code. It is best to oversize the pipe, If pulling in 3 #6 and a #8 ground 1 inch pipe may be sufficient but 1 1/4 inch would be better and allow for future upgrade in wiring for a larger service. A 60 amp panel can be fed with #6 which should be enough for a workshop if you are not going to get too radical with power usage. You can choose to not pull a Ground back to the main panel But you will need to drive a ground at the new panel and bond it to building steel and any metal water pipes in the new structure, also you will need to bond it to your neutral bar in the new panel. IF YOU DO PULL A GROUND DO NOT BOND IT TO THE NEUTRAL IN THE NEW PANEL. Do not exceed 360 degrees of bend in the pipe. Choose the proper overcurrent device. Install the Feed under a breaker in the Main panel sufficient for the load and in aggreement for the wire size being used. ie. 60amp breaker and #6 wire. Also it is a good practice to select a panel with a main breaker for the workshop. This will be a safer installation. The NEC code should be followed in any Electric Installation. Buy yourself a copy and read Section 250 on grounding. Grounding is very important in this and all installations. One more thing, Use either Gfi breakers in the workshop or Gfic receptacles, since you will undoubtedly be using power tools there. Good luck.

If you chose to use the PVC, your next question may be how to get a pull string in the conduit. 125' feet is longer than most standard fish tapes. I learned a slick trick watching some commercial electricians getting a pull string in to a long conduit run, Go to your nearest Craft store and pick up some fuzzy balls the same size or just a little larger than your conduit.. Then get a a 150' to 200' spool of light nylon line (kite string). Tie the ball to the string and **** it through the conduit with your shop vacuum. Use this to pull in your pull string and you are ready to go.

that is a good tip,but you can do the same thing with a small plastic bag. Take the bag and fill with a little air, then twist it off to the size of your pipe i.d. then tie it with the string and tape around it's opening to the string. Electricians call this a mouse. It may take an inexperienced person a couple of tries,but it works very well. If you do not use rigid 90's be sure to use a larger pull rope for the wire and have someone pushing the wire from the feed end. If you do not then the pull rope will eat into the pvc 90's and get stuck.

Thanks for the hints.

I was thinking I would run the pull string through each section of conduit as I glued it together.

But I was wondering?

What would be wrong with laying the wire out next to the trench then sliding the conduit sections on from one end one after the other and gluing them each in turn? That way I wouldn't have to "pull" any wire at all.

Thanks again.

Bill

If you try to do that there is a good chance the pvc glue will eat into the insulation on the wire. You will also find that this is a cumbersome undertaking and will not work well, the N.e.c. also states that all pipe shall be completed from end to end before wire is to be installed. In Short, this simply is not the way it is done.