I'm looking to help my grandparents underground their overhead power & phone lines as they currently run through the middle of a tree which is increasingly threatening the lines. They also need to replace the underground water pipe as it has developed a leak and volumetric water charges are coming in soon. Luckily they are on sand, so trenching shouldn't be too hard (Grandad dug all the service trenches himself 50 odd years ago).

We will be engaging an electrician at some point, but would appreciate a bit of GZ wisdom just to scope the project.

1) I'm familiar with the Chorus lead-in guide, I'm confident to run green conduit & 2pair gel-filled cable, but I get the feeling I should leave the actual connecting to Chorus? It's a bit difficult as the phone pedestal is across the road, so the overhead line goes from the house to the nearest pole, then across the road and down another pole to the pedestal. In this case would they just install a demarc style box on the nearest pole, so that the underground lead-in connects to the overhead leadin that runs across the road?

2) What scope is there to put power/phone/water in the same trench? I gather that power needs to be >600mm deep, phone >450mm deep, and the two separated >300mm. How far should water be from these two? I'm wondering if it's worth doing separate trenches rather than one big wide trench, given we will be digging by hand rather than with a digger.

3) With power I think the options are conduit + warning tape, or direct burial + magslab mechanical protection. What is typical for a leadin to standalone house? What size conductor would I typically use for this? There is a separate incoming line for ripple control, but I believe it is redundant as they use RF over power signalling.

TIA
Nick