I live in an apartment in Southern California. For the past three days at around 2:30am there has been a almost mechanical thumping noise in the walls. It's loudest in one of the bathrooms. It goes on for approximately 10 minutes then abruptly stops. It is only at this time of night. Our landlord called a plumber who tests the temperature of the water heater and said nothing was wrong. He just kind of shrugged. He said that if the noise continued to annoy us to call the landlord again. It is very annoying to be woken up by this sound every night at 2:30am. Does anyone have any insight into why this might be happening so we can tell our landlord what needs to be fixed?

How many other tenants are in this building? This could be caused by some automatic system like a water siftner or lawn sprinkler or even a tenant who showers very early for a early job. The bad news is this is the problem of the landlord to fix and he seems uninterested. Don't do any work yourself because you may make a mistake and be held liable.