How to Winterize Your Plumbing System Before It's Too Late

Winterizing the plumbing in a southern New Hampshire home is the difference between a comfortable winter and a flooded basement at 2 AM in January. The good news: most of the steps are simple, take a weekend or less, and last for years. The work to do now, before the first deep cold, protects pipes from freezing and prevents the kind of damage that takes weeks to clean up.

Here is a complete checklist from a NH plumber.

Before the first hard freeze (October to early November)

Disconnect and drain outdoor hoses

Water left in a connected hose freezes, expands back into the hose bibb, and can split the supply pipe inside the wall.

• Disconnect garden hoses from outdoor faucets
• Drain hoses and store indoors or in a shed
• If you have indoor shut-off valves for outdoor hose bibbs, close them and open the outdoor faucet briefly to drain the line
• For frost-free hose bibbs (newer NH installs), draining the hose is usually sufficient

Insulate exposed pipes

Foam pipe insulation is a few dollars per length and installs without tools. Focus on:

• Pipes in unheated basements, crawlspaces, and attics
• Pipes along exterior walls
• Pipes near vents, windows, or other cold infiltration points
• Hot water pipes (insulation reduces heat loss and energy use)

Seal air leaks near plumbing

Even insulated pipes can freeze if cold outdoor air is blowing directly on them. Caulk and seal:

• Around pipes that pass through exterior walls
• Holes in the rim joist where pipes enter the basement from outside
• Foundation cracks near plumbing
• Dryer vents, attic penetrations, and other obvious air leak paths near plumbing

Have your heating system serviced

If your boiler or furnace has not been serviced in over a year, schedule it before the heating season begins. A boiler that quits on the coldest night of the year is a frozen-pipe risk in addition to a no-heat emergency.

Locate your main water shut-off

Every household member should know where the main water shut-off valve is located and how to operate it. The valve is typically near where the water service enters the home or near the water meter. If you cannot find it, your plumber can show you on the next service visit.

During cold weather (December to February)

Keep the primary heating system running

Even if you primarily heat with a wood stove or pellet stove, keep the boiler or furnace running. Stoves heat the room they are in but do not protect pipes in basements, crawlspaces, exterior walls, garages, or unused rooms. Pipes in those locations can freeze sooner than you expect if the central system is turned off.

Maintain at least 60°F throughout the home

Do not set the thermostat far below normal even when away. Avoid large overnight setbacks during cold snaps; the savings are not worth the frozen pipe risk.

Open cabinet doors under sinks on exterior walls

Letting room air circulate around the under-sink plumbing helps prevent the cold spots where freezes typically start.

Open interior doors

Doors closed to unused rooms or rooms over garages can create cold pockets where pipes freeze. Keep them open during cold stretches.

Let cold-vulnerable faucets drip

For fixtures on exterior walls, or fixtures that have frozen in the past, let a small stream of cold water trickle overnight during the worst cold. Moving water is harder to freeze. A pencil-lead-thin stream is enough.

Watch for warning signs

• Little to no water flow from a faucet
• Frost visible on exposed plumbing
• A room that is noticeably colder than the rest of the home
• Strange noises in the walls (especially banging or hammering)

If you will be away for an extended period

For trips of a few days

• Set the thermostat to no lower than 60°F
• Have a neighbor or friend check the home daily
• Let exterior-wall faucets drip
• Open cabinet doors under sinks on exterior walls

For longer absences or seasonal homes

• Consider shutting off the main water supply at the meter
• Drain plumbing lines by opening faucets after the shut-off
• Drain water heater (or set to vacation mode if available)
• Add non-toxic RV (propylene glycol) antifreeze to drains and toilet bowls to prevent trap freezing. Never use automotive antifreeze, which is toxic to people, pets, and septic systems.
• For homes with hydronic heat, have a plumber add antifreeze to the heating system if there is genuine risk of system loss
• Install a smart water leak detection system (Moen Flo, Phyn) for remote monitoring and automatic shut-off if a leak is detected while you are away

What to do if a pipe freezes

1. Open the faucet served by the frozen pipe so meltwater has somewhere to go
2. Apply heat gently with a hair dryer, heating pad, or space heater, working from the faucet toward the frozen section
3. Never use an open flame (torch, propane heater). Plumbing fires are a real and dangerous risk.
4. Once water flows, leave the faucet at a trickle until the pipe is fully thawed and you have addressed the cause

What to do if a pipe bursts

1. Shut off the main water supply immediately
2. Shut off the heating system if a hydronic (boiler) pipe burst
3. Turn off electricity to areas where water has reached outlets or equipment
4. Open faucets to drain remaining water from the lines
5. Call a licensed plumber
6. Call your insurance carrier if there is significant water damage

Schedule a winter readiness assessment

If you want a plumber to walk through your home before winter and identify vulnerable plumbing, contact A.J. LeBlanc Heating. For 24/7 emergency plumbing service, call 603-623-0412. Serving New Hampshire families since 1928.

Frequently Asked Questions

At what temperature do pipes start to freeze?

The conventional rule is that the pipe environment needs to drop below 20°F for several hours before freezing becomes a real risk. Pipes in well-insulated interior walls of a heated home rarely freeze.

What is the lowest safe thermostat setting in winter?

60°F. Below that, the risk of frozen pipes (and the cost of recovering an iced-out heating system) outweighs the savings.

Should I leave faucets dripping during cold snaps?

For at-risk fixtures (exterior walls, history of freezing), yes. A pencil-lead stream of cold water is enough to prevent freezing.

Can I use a propane torch to thaw a frozen pipe?

No. Plumbing fires from torches are a real risk, especially in older walls with combustible insulation or wood framing. Use a hair dryer, heating pad, space heater, or call a plumber.

Will my insurance cover a burst pipe?

Most NH homeowner's policies cover sudden burst pipe damage, but not damage from chronic leaks or freezing in a vacant home where the heat was turned off. Check your specific policy.