Unlike pressurized water supply lines, drain pipes are not always full of water. They freeze when water sits stagnant in a low spot or when the pipe has a shallow slope. Common culprits include:
2021 note: With more people working from home due to the pandemic, households are using more water irregularly. Strangely, less water flow at night (when everyone is asleep) allows drains to freeze solid by morning.
If the pipe is inside a cabinet or a crawl space where you cannot easily pour water: how to unfreeze a drain pipe 2021
If the above fail after 45 minutes, try this plumber’s trick:
Pipe Heating Cable (Retrofit type)
Best for large frozen sections in open areas.
Do not leave the heater unattended – this is critical. Unlike pressurized water supply lines, drain pipes are
Once water starts flowing again:
If you’ve tried gentle heat for 2 hours and the pipe remains frozen: 2021 note: With more people working from home
Emergency plumbers in 2021 are busier than ever (thanks, COVID staffing shortages), but a frozen drain is worth the call before it becomes a flood.
Gather these before you start: