Under what circumstances can I break a lease early?

You cannot 'break' the lease, at least not easily. The best way to handle this is to file a "Tenant's Assertion" in General District Court and pay your rent to the court, not to the landlord. MAKE SURE YOU SUE THE OWNER not a management company or agent. Get pictures and show the damage being done - especially if the leaks are harming your stuff. You can also call the building department for the jurisdiction in which you live (I presume the City of Alexandria) and have them inspect the leaks - they can require the owner to fix them and if there are problems can be a helpful witness in court. The court can let you out of the lease or reduce your rent or do nothing. It may be helpful to consult a landlord tenant attorney - there are several on from your area.