HELP...Water Leak from Upstairs Unit

[Roger T.]

Greetings,

I hope you are all well and safe! 

Here's my situation:

I own the bottom unit on a 2 story condo in Concord, CA. My tenant notified me yesterday that there has been a water leak (from upstairs unit) which damaged the ceiling to our unit. He went upstairs and the tenant said there is a toilet and sink above the damaged ceiling (see picture below) but they did not find any issues or leaks. I would need to open my ceiling and flush their toilet and run their sink to see if there's a leak coming from their unit. 

At 10:30 am this morning, I contacted the landlord of the unit upstairs and she said she could not be there when my contractor arrives this coming Thursday, March 25, but she will ask her mother if she could open the door for us (it has to be this Thursday because that's when the contractor is available and when my tenant is off from work). 

I waited several hours and since I did not hear back, I sent a text message at 1:30 pm with the pictures of the damage and asked if they could be available for the contractor and she still hasn't responded. My sister suggest I wait 24 hours because the appointment is till 4 days and to be patient.

Here are my questions/concerns:

• - What if the landlord doesn't comply, is unresponsive or uncooperative? Are there any laws granting me permission to access their unit to find out where the leak is coming from? 
• - What steps should I take next if she does not answer my text/calls?
• - I called the HOA and they said that if the pipe is servicing my unit then it is my responsibility and if the pipe is servicing their unit, then it is theirs. The HOA is only responsible for the pipe that goes to both units. I read the covenants, conditions and restrictions and it states that the Common Area is "conduits, pipes, plumbing, wires and other utility installations (except the outlets thereof when located with-use of two (2) or more units which may protrude into the airspace of a unit;" Does the HOA hold any responsibility?

I would prefer to keep it friendly and professional with the landlord upstairs, but I am willing to seek legal assistance if necessary. I am a bit anxious because this is water damage and it looks like black mold is growing, plus I want to prevent further damage and I never dealt with another landlord before. 

I would appreciate any and all advice or opinions. Thank you in advance!