Irrigation pressure regulator?

I would not put them below ground. You should have the pressure regulator installed right after the filter and I would put an elbow in there to leave them above ground or install the head assembly in an irrigation box to leave access to it.Personally I like to leave every thing above ground for easier installation and maintenance. I don't think that the regulator should be leaking any water. Check to see if the leak is coming from the regulator or from around the threads. If it is coming from around the threads you probably have hose threads on one piece and pipe threads on the other. The two are not compatible and you will have to buy a new connection to make sure that the threads on both are the same. (Hose threads appear just a little more coarse.)