It’s important to remember the definition of your lot. It’s the cubic space within the dark lines on the strata plan. And it’s between the floor surface and the bottom of the ceiling.
Therefore if the pipes or meter are in the cubic space, it’s lot owner responsibility.
If the pipes are embedded in the common property walls or floors or ceilings, they are OC responsibility.
Sometimes it doesn’t make sense, but the definitions have to be framed somehow so thst owners and OC aren’t going to court for the court to decide who is responsible for what.