California Code, Civil Code - CIV § 1942.1

Any agreement by a lessee of a dwelling waiving or modifying his rights under Section 1941 or 1942 shall be void as contrary to public policy with respect to any condition which renders the premises untenantable, except that the lessor and the lessee may agree that the lessee shall undertake to improve, repair or maintain all or stipulated portions of the dwelling as part of the consideration for rental.

The lessor and lessee may, if an agreement is in writing, set forth the provisions of Sections 1941 to 1942.1, inclusive, and provide that any controversy relating to a condition of the premises claimed to make them untenantable may by application of either party be submitted to arbitration, pursuant to the provisions of Title 9 (commencing with Section 1280), Part 3 of the Code of Civil Procedure, and that the costs of such arbitration shall be apportioned by the arbitrator between the parties.