Yes, let faucets drip when the outdoor temperature is heading toward 20 degrees Fahrenheit or below, especially overnight.
It is one of the few winter habits that is genuinely worth the water, and it costs less than a takeaway coffee.
But most advice gets the reason wrong, which leads people to drip the wrong taps or to stop too early.
Here is the temperature to start at, which faucets to open, how much to run, and what dripping does not protect you from.
When to let faucets drip, by outdoor temperature
Pipes do not freeze at 32 degrees. The house holds heat, and the pipes inside it lag well behind the air outside.
The number that matters is 20 degrees Fahrenheit, and it is the point at which pipes in unheated spaces begin to freeze.
Start dripping when the forecast low reaches about 20 degrees, or sooner if the cold will last more than a few hours.
Drip earlier, at nearer 25 degrees, if your home is on piers, has an uninsulated crawl space, or lost a pipe in a past freeze.
Wind matters more than people expect. A hard wind on an exposed wall pulls heat out fast and moves your threshold up.
Keep it running until the temperature is back above freezing and staying there, not just for the coldest hour of the night.
For the full picture on thresholds, see at what temperature pipes actually freeze.
Why you let faucets drip: pressure, not motion
The popular explanation is that moving water cannot freeze. That is mostly wrong, and it leads to bad decisions.
In a hard enough freeze, water in a pipe will form ice whether it is trickling or not.
What actually bursts a pipe is not the ice itself. It is the pressure trapped between the ice plug and a closed faucet.
As the plug grows, it pushes the water ahead of it. With nowhere to go, that column of water builds enormous pressure.
The pipe then splits at its weakest point, often well away from the ice, which is why the burst is rarely where you expected.
An open faucet gives that pressure somewhere to escape. The drip is a relief valve, and that is the whole mechanism.
It follows that an open tap helps even if the line freezes anyway, which is exactly why you leave it open through the cold.
Where pipes actually freeze in a house
Knowing this is what turns a guess into the right two taps.
Pipes freeze where the heated envelope of the house ends. Anywhere the plumbing steps outside that boundary is a candidate.
- Runs inside exterior walls, especially where insulation was pushed behind the pipe instead of around it
- Unheated attics and the supply lines to an upstairs bathroom above a garage
- Crawl spaces and unheated basements, particularly near an open vent
- Garages, porches, and unheated additions built on after the original house
- The kitchen sink on an exterior wall, which is the single most common freeze point
Go find yours in daylight, before the cold arrives. A flashlight in the crawl space now saves a 2 a.m. emergency later.
Feel the cabinet under the kitchen sink on a cold evening. If it is noticeably colder than the room, that is your first drip.
Which taps to open, and how big the drip should be
You do not need every faucet in the house. Pick the ones that are actually at risk.
- The faucet farthest from where the water line enters the house, so the drip pulls through the whole run
- Any faucet fed by pipes running through an exterior wall, an unheated attic, a garage, or a crawl space
- Kitchen and bathroom sinks on the coldest side of the house, usually the north or the windward side
- Any fixture that has frozen before, because the same pipe will freeze first again
The right size is a slow trickle, not a stream. Think the width of a pencil lead, or a few drops a second.
A tiny drip that stops overnight is worse than none, because you will believe you are protected. Check it before bed.
Put a bucket or a jug in the sink and reuse the water for plants or the toilet if the waste bothers you.
Should you let faucets drip on hot and cold lines?
Open both. This is the detail most homeowners get wrong.
The hot line is full of standing water once the heater stops firing, and standing hot water freezes just fine.
On a single-lever mixer, set it to the middle so both lines feed the spout at once.
On two-handle taps, crack each handle separately. One handle only protects half of the plumbing under that sink.
Cold lines are still the higher risk, because they run further and are more often routed through unheated space.
What to do alongside the drip
Dripping is one layer. On its own it will not save a pipe in a badly exposed wall.
- Open the cabinet doors under the kitchen and bathroom sinks so room heat reaches the pipes
- Keep the thermostat at one temperature day and night, and never below 55 degrees
- Close the garage door and keep it closed, especially if plumbing runs through that wall
- Disconnect garden hoses and shut the valve feeding each outdoor spigot
- Add foam sleeves to any exposed pipe in a crawl space, attic, or unheated basement
The cabinet doors matter more than people think, because a sink cabinet is a cold pocket cut off from the room.
If you have small children or pets, move the cleaning products out before you leave those doors open.
The full set of measures, including the away-from-home rules, is in how to prevent frozen pipes from bursting.
How long to keep the taps dripping
Longer than the cold snap itself. The materials around the pipe stay cold well after the air warms up.
Keep dripping until the outdoor temperature has been above freezing for a full day, not just above freezing at noon.
A crawl space or an attic can sit below freezing for a day or two after the outside air has recovered.
During a multi-day event, do not stop and restart each morning. Leave it running through the whole stretch.
Check each open tap morning and night. Aerators clog, handles get bumped, and a stopped drip protects nothing.
What dripping actually costs you
Far less than people assume, and a rounding error next to a burst pipe.
A tap dripping once a second wastes on the order of 8 gallons a day, which is a few cents on most water bills.
Across a week-long cold snap with two taps open, you are looking at a dollar or two, not a noticeable bill.
Compare that with the average insurance claim for water damage and freezing, which runs into five figures.
The math is not close. Read what a burst pipe claim involves if you need convincing.
When dripping is the wrong move
There are a few cases where a drip is useless, or where it creates a second problem.
- Outdoor spigots and hose bibs, which should be drained and shut off rather than left running
- A vacant home you are leaving for weeks, where draining the system down is the safer answer
- A well and pump system, where continuous draw can cycle the pump all night
- A drain line that runs through unheated space, which can freeze from the trickle itself
On a septic system, a week of dripping adds volume to the tank. It is usually fine, but keep the drip small.
If a drain does freeze, the sink backs up rather than the pipe bursting, which is annoying but far cheaper.
And if you are leaving for the winter, dripping is not a plan. Shut the water off at the main and drain the lines.
What to do if a pipe already froze
No water at one fixture while the rest of the house works normally means that line is frozen.
Leave the faucet open. Once the ice starts to melt, the open tap gives the water and the pressure somewhere to go.
Warm the pipe gently with a hair dryer, a heat lamp, or towels soaked in hot water, working from the faucet backward.
Never use a blowtorch, a propane heater, or any open flame. That is how frozen pipe calls become house fire calls.
Know where your shutoff is before you start thawing, because a split pipe announces itself the moment the ice clears. Find the main shutoff now.
When to call a plumber
Call if you cannot find the frozen section, if the pipe is inside a finished wall, or if thawing has not worked in an hour.
Call immediately if water appears anywhere once the line thaws, and shut the main off first.
If a pipe has already split, the clock is on the water damage, not the plumbing. The burst pipe first steps come next.
Pipe already split, or water in the ceiling after a freeze? Getting it dried in the first 48 hours is what keeps the repair small.
(844) 502-1354Common questions
At what temperature should I start dripping my faucets?
Around 20 degrees Fahrenheit, which is the point at which pipes in unheated spaces start to freeze. Start sooner if the cold will last, if it is windy, or if your pipes are poorly insulated.
Should I drip hot water, cold water, or both?
Both. The hot line holds standing water between heating cycles and can freeze too. On a mixer tap, set the lever to the middle so both supply lines are open.
How many faucets do I need to leave dripping?
Usually one or two. Pick the fixture farthest from where water enters the house, plus anything fed by pipes in an exterior wall, attic, garage, or crawl space.
How much water does a dripping faucet actually waste?
A drip about once a second is roughly 8 gallons a day, or a few cents. Even a week of dripping through a cold snap costs a dollar or two.
Can a pipe still freeze while the faucet is dripping?
Yes. In a hard freeze, water can freeze even while moving. The open tap still helps, because it releases the pressure that actually splits the pipe.
Should I drip the outdoor spigot too?
No. Disconnect the hose, shut the interior valve that feeds the spigot, and drain it. Leaving an outdoor tap running invites a frozen bib and an icy walkway.
Sources
- Fix a Leak Week, household leaks and dripping faucets — U.S. Environmental Protection Agency, WaterSense
- Facts + Statistics: Homeowners and Renters Insurance — Insurance Information Institute
- Preventing and Thawing Frozen Pipes — American Red Cross
- Field research on the temperature alert threshold for residential water pipes — Building Research Council, University of Illinois
- Freezing and Bursting Pipes — Insurance Institute for Business and Home Safety (IBHS)
- Cold Weather Safety — National Weather Service
- Drip Calculator and Water Density and the Expansion of Ice — U.S. Geological Survey, Water Science School
- ANSI/IICRC S500 Standard for Professional Water Damage Restoration — Institute of Inspection, Cleaning and Restoration Certification
