I need to know what to do to make my landlord fix the plumbing!?

I live in the SF Bay Area. My shower drain and toilet keep bubbling up waste water and sewage. It keeps flooding my bathroom. My landlord has been here several times trying to fix it himself but it obviosuly needs a professional. Now the landlord either ignores my calls and isnt fixing it. What can I do to make him get a pro to fix it asap. It's not even livable in here.