You must have given a written request for repairs to be done in a certain amount of time which is set according to the law of state. You can cancel the lease if landlord doesn't make repairs or you can make repairs by your own and deduct the amount from the rent due.

 Most states such as California also allow you to withhold a percentage of your rent due to uninhabitable conditions, such as plumbing, heating, electrical issues etc. As stated it is required, and just plain good idea that all request for repairs be made in writing, so that when using any of the remedies such as withholding rent, or deducting for repairs, your landlord cannot retaliate against you in any way.