Culver City is largely mid-century housing with newer multi-family and commercial mixed through it, and the older residential stock is mostly slab construction of that era.
Copper supply from that period is now old enough to develop pinhole failures, and a pinhole under a slab or inside a wall runs for a long time before it surfaces.
What goes wrong in Culver City properties
Slab leaks and in-wall supply failures lead the residential work. In the newer multi-family and commercial buildings it is more often a fixture failure or a supply connection.
Ballona Creek and the low ground near it matter in a heavy storm. Where the drainage backs up, water arrives at properties across the ground rather than through any plumbing.
I heard running water at night with everything off.
That is one of the more reliable slab leak symptoms. Check the meter with every fixture closed; if it is moving, water is going somewhere it should not.
Is a pinhole leak urgent if it is only a drip?
Yes, because it is inside a wall or under a slab and it never stops. A slow leak running for weeks does more damage than a burst pipe caught in an hour.