

Mapei grouts don't need sealing. They're formulated to resist water and stains as is. You should, however, seal around the edges of your tiles in wet areas to ensure a watertight result.
Mapei grout sets in about 24 hours. However, it's best to wait three to four days before exposing it to water to allow it to fully cure.
Mapei Ultracolor Plus is water-repellent but not completely waterproof. It's suitable for most bathroom and kitchen applications. For areas that are constantly wet, like pool surrounds, Mapei's epoxy grout might be a better choice.