May I assume you are using the water supply for both irrigation and household use? If so, then you need a true back flow preventer to prevent cross contamination. A check valve does not qualify for cross contamination protection. You will want to tee off of the household supply line below frost level and put in a stop and waste valve with the key access above ground level. The irrigation line need to come up toward the surface and if you use a double check back flow preventer, that can be below ground level if you desire, but you do need to have access to it for winterizing. After the back flow preventer, you can go to a manifold where the zones are split off and the electric valves are located. In my setup, I have the BFP in a box set at ground level. I remove the BFP in the winter and blow the water from the lines from the BFP connecting union. I store the BFP indoors just to be certain it does not have a trace of water that can freeze. The BFP should be tested and certified annually as they do wear and occasionally need new seals. This must be done by a certified inspector, it is not a DIY job.