The answer to 'why is my drain frozen' is that a drain can freeze due to cold temperatures, especially in the winter months. When water in the pipes freezes, it expands and blocks the drain, preventing water from flowing freely.
Common causes of a frozen drain include outdoor pipes that are exposed to cold air, drains located in unheated areas like the basement or crawl space, and drains that have poor insulation or ventilation. Symptoms of a frozen drain include slow or no water drainage, gurgling sounds, and sometimes visible ice buildup around the drain.