It doesn't need to be big. It will just lay with the pipe unless you ever need to use it for someone to hook a locater to it to mark your water line. Just leave a foot or two in the meter box and zip tie it to the water line on your side of the meter. It doesn't need to be hooked to anything. You can zip tie it to your water line every 6 or 8 feet before you toss the line in the ditch. Then just run it up the wall where the water line enters, or just tape it to the water line and poke it thru the sleeve into the basement. Its sole purpose is to be in the ditch with the plastic water line, so there will be something metallic to hook to with an electronic locater to find exactly where the line is 20 years from now, if you need to dig and don't want to cut it. A locate machine is pretty much a transmitter and receiver. You hook the transmitter to one end of the wire, then use the receiver to follow the path and mark. If you ever have to use it for locates even once, it will be worth the cost of the wire. If you know any guys who work for the cable tv or telephone company, they may be able to snag you what you need. Gas company guys are even better sources, because they have rolls of wire specifically for that purpose because they us it on all plastic gas lines. Home Depot probably has spools of #6 copper. I've suggested it because I wish I'd done it when I built my house. I needed to dig up the lid of my septic tank a few years ago to have it pumped and thought I knew exactly where to dig. It had been way too long since the last pumping.....and I dug 4 or 5 practice holes before I gave up and ran a long piece of guy wire down thru a cleanout and hooked a locater to it. I was off by 10 or 15'....lol. I kinda/sorta know where my water line is, but I hope I never have to dig it up. Everything you can do now to make it easier on the "Old" you 20 or 30 years from now if this is your forever home, you won't regret.