You really want pea shingle around the water main, then back fill with earth to around 6-9" from finish level. From here you want lay around 7" of type one & really compact this down "preferably with a wacker plate". Then put 1" of 14mm natural gravel on top to finish. I have this as a drive & pulling the bins across it is fine if you don't make the gravel finish to deep. You could us crushed concrete instead of type one, but you might have to through out the bigger lumps or break them up. But will be cheaper.
Don't worry about the wacker plate, just don't use where the pipes are getting near the surface, do this by hand. The wacker "if a small one" only works around 2" down, so you should put the type one in a couple of inches at a time & build it up. If you don't, you will end up with an uneven path a few months down the line when it settles.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!