You generally want to leave the cold water dripping, not the hot, when you’re trying to protect pipes from freezing in very cold weather.

Quick Scoop: Hot or Cold?

When you’re worried about pipes freezing and you decide to let a faucet drip overnight, the usual advice is:

  • If you can only drip one line: drip cold water.
  • If it’s extremely cold and you’re really at risk: dripping both hot and cold can offer extra protection, especially if both sets of pipes run through unheated or exterior areas.

A simple way to think of it: cold lines are usually closer to exterior walls and more likely to freeze first, so they get priority.

Why dripping works (in simple terms)

  • Moving water is less likely to freeze than still water, so even a small trickle helps.
  • A dripping faucet can also relieve pressure in the line if some ice does form, which helps reduce the chance of a burst pipe when things start to thaw.

A tiny stream about the size of a pencil lead is usually enough; you don’t need a big flow.

Practical tips you can actually use

  • Start dripping when temps drop near or below about 20°F (around -6°C), sooner if you have poor insulation or exposed pipes.
  • Focus on:
    • Faucets on exterior walls
    • Pipes in unheated spaces (garages, crawlspaces, basements)
  • If your water heater is in a very cold area, running hot water for a minute now and then (like before bed and in the morning) can help keep that hot line moving too.

Little “story-style” example

Imagine a cold snap hits a place like Dallas or Houston, where homes aren’t really built for long, hard freezes. Local homeowners are told to crack their faucets open just enough so the cold side drips overnight. Most of them only drip cold water to avoid wasting energy heating water they’re just sending down the drain, and that tiny cold drip is often enough to get them through the night without burst pipes and a massive repair bill.

Mini FAQ

Does it have to be cold water?
No. Any moving water helps, but cold is usually recommended because it doesn’t cost extra gas or electricity the way hot water does.

What if my area is in a serious deep freeze?
Then dripping both hot and cold on vulnerable runs (like exterior walls) is reasonable if you’re very worried about freezing.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.