When replacing or repairing a toilet flange, you'll find that you'll need to apply mortar around the edges of the flange. This will provide a waterproof seat for the bottom edge of the toilet. In applying your mortar, you'll need to know how long the mortar should be allowed to dry, or cure.
Cure time for toilet flange mortar will depend on the type of mortar you use. You should check for recommended cure time on the container of the mortar you use. One of the most effective mortars for this use is an epoxy mortar. Cure time for this mortar is usually 4 hours when room temperature is 70 degrees F.