What is a reasonable period of time?
This depends on the defects and the types of repairs that are needed. The law usually considers 30 days to be reasonable, but a shorter period may be considered reasonable, depending on the circumstances.

For example, if tree roots block the main sewer drain and none of the toilets or drains work, a reasonable period might be as little as one or two days.

If the landlord doesn't make the repairs within a reasonable period of time, the tenant should notify the landlord in writing of the tenant's reasons for moving and then actually move out. The tenant should return all the rental unit's keys to the landlord.

The notice should be delivered via certified mail. The tenant should keep a copy of the notice. It's a good idea, but not a legal requirement, for the tenant to give the landlord written notice of the tenant's reasons for moving out. The tenant's letter may discourage the landlord from suing the tenant to collect additional rent or other damages. A written notice also documents the tenant's reasons for moving, which may be helpful in the event of a later lawsuit.

If possible, the tenant should take photographs or a video of the defective conditions or have local health or building officials inspect the rental unit before moving. The tenant should keep a copy of the written notice and any inspection reports and photographs or videos.