How much water pressure do you have at your house? Is the house lower in elevation than where the meter is? As water goes downhill, water pressure increases. If water pressure is over 60psi at the house, you risk water flowing past the valves in the toilets. This is very common and a big reason for massive water bills.
Since you put a valve just before the house, how sure are you that the valve in stopping the water? Especially if you are downhill and have high water pressure?
Gasketed pipe sounds like what you have. They are designed to move in and out of each other so the pipe doesn't break during the freeze thaw cycle of the soil. Every City Water Line uses this type of pipe. It is the best material for long distances. Anything over 500 should be able to move.
Black Poly is probably the very worse material ever invented for plumbing. It works great until the day it fails. It fails all the time from fatigue caused by movement. In short runs, the odds of failure decrease, but in long runs, it becomes more and more likely to happen. I understand that everyone who has used it will tell me that I'm wrong. This comes from City Water Departments that I've spoken to personally, and it's based on National Date that they have on what works and what to avoid. If you have it, be aware of issues. Saying it's worked for you so far does not mean it's a good product.
If water pressure isn't too high, the next question is, how old is your meter? How old are your City Water Supply pumps? Surging is when the pressure in the water mains increases and decreases. When the pressure decreases, the water in the lines is sucked backwards. This can be a constant thing in older systems. Backflow valves are mandatory in a lot of systems because the water flowing backwards can actually draw in contaminates from outside the water lines. Garden hoses do this all the time.
If your meter is old, or defective, that water flowing backwards from the pressure changes from the older pumps will cause the meter to turn every time the water pressure increases and moves that water back towards your house. This can be minor and add a little to your bill, or it can add hundreds of dollars to your bill.
In my experience, the Water Department will deny this is happening on their systems because that would mean they know it's causing people to over pay on their bill. I've also found that when I brought this up to the person in charge of the Water Department, the meter magically gets changed in a day or two, and the problem never happens again.
If your water pressure is good at the house, and you have a newer water meter, then you have two options for finding the water. Digging and exploring the length of the pipe, or hiring a pro to come out and find it for you. I've done both. If it's a really long line, hiring the pro is money well spent.
