Preventing Frozen Pipes in a New Hampshire Winter

A frozen pipe is an inconvenience. A frozen pipe that splits is thousands of dollars of water damage, and it usually happens while nobody is home.

Water expands when it freezes. That expansion has to go somewhere, and in a closed pipe it splits the pipe or a fitting. Here is the part people miss: the pipe usually does not leak while it is frozen, because the ice is plugging the hole. It leaks when it thaws. So the damage happens after the cold snap breaks, often when somebody is finally back in the house and cranks the heat.

Where it happens

Not randomly. Freezes cluster in predictable spots:

• Exterior walls, especially where somebody ran supply lines through an outside wall to reach a kitchen sink
• Crawlspaces and unheated basements
• Garages, particularly a laundry sink or a hose bibb on a garage wall
• Attics, where somebody ran a line for an upstairs bath
• Under kitchen sinks on outside walls, which is a classic
• Outdoor hose bibbs that were never disconnected in the fall
• Vacation properties and camps on minimal heat

Wind matters more than people expect. A twenty degree night with hard wind on an exposed wall does more damage than a ten degree calm night, because wind strips heat off the building surface.

Before the cold

Disconnect the hoses. Every fall, no exceptions. A hose left connected traps water in the bibb and holds it against the valve. Frost free hose bibbs are only frost free with the hose off, because the whole design depends on the line draining back past the frost line. This is the single most common freeze we see and it is entirely preventable.

Know where your main shutoff is. Everyone in the household who is old enough should know. Test that it actually turns. Old gate valves seize, and finding that out during an emergency is a bad time.

Insulate pipe in unheated space. Foam sleeves from any hardware store. Cheap, and it buys you real margin. Insulate the pipe, not just the space.

Air seal near the pipes. Insulation without air sealing does not do much. A rim joist with a gap to the outdoors will freeze a pipe through insulation. Find the drafts and seal them.

Heat tape where it makes sense. Use a UL listed cable made for water pipes, follow the instructions exactly, and do not overlap it on itself. Plug it into a GFCI. Replace old cable rather than trusting it, because failed heat tape has started fires.

Open the cabinet doors under sinks on exterior walls during a cold snap so room air can reach the plumbing.

During a hard freeze

Let a faucet drip. Moving water freezes at a lower temperature and, more importantly, a dripping faucet relieves pressure. Even if ice forms, the pressure that would split the pipe has somewhere to go. Pick the fixture farthest from where the water enters the house, and use a slow steady drip on the cold side, or both sides if that fixture is served by both.

Keep the heat up. Not the week to try a deep setback. If you are going away, do not set the thermostat to 50. Sixty is a reasonable floor, and it costs far less than a burst pipe.

Going away for a while? Either have somebody check the house every couple of days, or shut the water off at the main and drain the system. On a camp, winterize it properly with antifreeze in the traps.

If a pipe is already frozen

Symptom is no water, or a trickle, from one fixture while others work.

1. Open the faucet that pipe feeds. Gives melting water somewhere to go and relieves pressure.
2. Find the frozen section. Follow the line toward the unheated area. Frost on the outside of the pipe, or a section that is colder than the rest, or a visible bulge.
3. Warm it gently. Hair dryer, heat gun on low, warm towels, a space heater aimed at the area. Start at the faucet end and work back toward the frozen section, so meltwater can escape rather than getting trapped behind more ice.
4. Never use an open flame. Torches on frozen pipes cause house fires every winter, and on top of that you can steam explode a section of trapped water.
5. Watch for leaks as it thaws. Stay there. Be ready to shut the main off.

If you cannot find it, cannot reach it, or you see water once it starts moving, shut the main off and call.

The one nobody thinks about

If your heat goes out in January, the clock on your plumbing starts running. A house without heat in single digits can freeze pipes within a day depending on the construction.

If you lose heat and cannot get it restored quickly, shut the water off at the main and open the faucets to drain the system. Cleaning up a cold house is much easier than cleaning up a flooded one.