Replacing Main Water line

Two years ago I purchased a home built in 1940. This past March, I was notified by the city that my main water line was probably leaking, as my home had used 198,000 gallons of water. After figuring things out with the City, I was told that if I repaired/replaced my main water line I would not be held accountable for the leaked water. I paid a plumber to patch the leak, and left the pipe exposed for the summer while I decided if I was going to undertake pipe replacement or not.

Recently, I decided to follow through with replacement and have notified the city. After little response, I went ahead with the project (as winter is approaching) and I hired a friend's father (who is a landscaper) to dig my main water trench. He suggested installing schedule 40 PVC pipe and began laying the pipe. MIdway through the project, the city came out to finally mark the other utility pipes. My issue is now two-fold:

First, I am told I need to procure necessary "permits" to pursue further replacement of my water main. Also, I am told that the depth at which we have buried the pipe (approx 28-34 inches) is insufficient and they recommend I go "at least 4 feet deep." I have heard from numerous sources around where I live (Eastern Oregon-- near Boise, ID) that the ground should not freeze at that depth, but as a first timer in issues of this nature, I do not know who to trust. I do not want to have to put excess labor into this, so I would like to get it right, but with a portion of the pipe already buried, it is unclear if the best thing to do would be to proceed with the project as it has been started, or to stop now, obtain necessary information, dig up the previously laid pipe, and do it again.

Any insight?

Generally, if the inspector wants the pipe a certain depth, you don't have much choice I think.

Any local plumbing company should be able to tell you what the depth needs to be to meet code in your area so should the inspector. I would also find out if PVC is allowed to be used for the water piping. It is not allowed here and I don't know of any where it is allowed.

A person marking utilities may not know the required code. You need to find the answer to the 2 questions B4 you proceed and maybe waste more time and $$$.

pipe

If it were not allowed here, most houses would not have a main water line. The city code will determine how deep it has to be. Once you have the permit, you will need a visual inspection of the line by the inspector. If it is not deep enough, according to the code, you will have to dig it up and lower it, regardless of whether you think it is deep enough or not.

Now I can say I know 1 place PVC water pipe is allowed, Arizona.