If your landlord has failed to keep your rental unit livable, you may be able to stop paying rent until the repairs are made. Your right to withhold rent—and the specific procedures you must follow to do so—vary from state to state. See the Nolo article How Rent Withholding Works for advice and rent withholding laws by state. In most states, tenants must give landlords written notice of the problem and of their intent to withhold rent. We include here a Sample Letter Telling Landlord of Intent to Withhold Rent that is for California tenants. If you are not a California tenant, consult your state law before writing a similar letter to your landlord.
For details on tenant rights to rent withholding and other options if a landlord fails to provide habitable premises, see Every Tenant's Legal Guide or (if you're renting in California), California Tenants' Rights.