You have to disconnect the line from the breaker and connect this to it so if you are not comfortable opening your panel and taking the line off the breaker, then this won’t be an option.
Also, I’m not endorsing this product, I’ve never used this one in particular, but it looks like the cheapest one that might possibly work for that depth… it says it detects up to 1 meter. Usually residential lines going to detached buildings are 24" but I’ve seen them deeper and I also have seen them barely scratched into the dirt a couple inches too, just depends on the contractor that put it in when your building was built initially.
They will not mark the private lines that go on your property. Water and sewer lines are usually customer owned after the curb. Oftentimes gas and buried electric and communications as well.
And to expand on this and give more examples of private utilities just so people have an idea of what is around their house: landscape lighting, sprinkler systems, invisible dog fences, power/gas/water lines ran to a detached garage/shop/shed/pool/garden/greenhouse from the house, driveway alarms/bells, and motorized gates. If you live out in the country and you have a propane tank for gas, a septic system, and a well for water… those will not get located for free by 811 either, those are also private utilities that will require you to hire a locator to do for you.
I buried drops for an ISP one summer long ago, so I have a tiny bit of experience with the locate process and burying lines.
