Insulate the line, run it to an interior drain, or install a condensate pump with heated line. 8. Key Takeaways | True / False | Statement | |--------------|------------| | ✅ True | Drain pipes can freeze if water sits in them. | | ✅ True | Unheated crawlspaces and exterior walls are high-risk. | | ❌ False | Drains freeze as easily as supply pipes (they don’t – less standing water). | | ✅ True | A frozen drain will cause backups, not immediate flooding (unless cracked). | | ✅ True | Prevention (insulation, slope, heat tape) is easier than repair. | | ❌ False | Running cold water helps prevent freezing (warm water is better). | Final Verdict Yes, drain pipes can freeze , but it typically requires a combination of subfreezing temperatures, standing water, and poor insulation or slope . The most vulnerable are kitchen sinks on exterior walls, condensate lines, and drains in unheated crawlspaces or attics. Regular maintenance, proper insulation, and occasional warm-water flow during extreme cold spells are the best defenses. If you suspect a frozen drain, thaw gently and inspect for cracks before resuming normal use.