How to Winterize a Seasonal Home in New Hampshire Before the First Deep Freeze

Seasonal homes, camps, lake houses, and cottages are part of life in New Hampshire. They also have to withstand long periods of freezing temperatures, snow, ice, and winter power outages. When a home sits empty through winter, even a small amount of trapped water can turn into cracked pipes, damaged pumps, ruined fixtures, septic problems, or heating system failures.

A proper winterization is more than turning down the thermostat and shutting the door. It protects the plumbing, heating, well, water treatment, appliances, septic system, and outdoor equipment before cold weather has a chance to cause damage.

In our experience servicing New Hampshire homes, freeze damage often starts in places homeowners cannot easily see: a low section of piping, an appliance valve, a filter housing, a pump casing, or a line running through an unheated crawlspace.

Here is what New Hampshire homeowners should know before closing a seasonal property for winter.

Why Seasonal Home Winterization Matters So Much in NH

New Hampshire winters can bring long stretches of freezing temperatures, heavy snow, ice buildup, and power outages. Seasonal homes are especially vulnerable because no one may notice a problem until weeks or months later.

Freeze damage is not always obvious while a pipe is frozen. Leaks may appear only after the pipe thaws and the plumbing system is repressurized. That can lead to soaked floors, damaged ceilings, ruined cabinets, mold concerns, and expensive emergency repairs.

The exact winterization process depends on whether the home will be completely shut down or kept heated through winter. The goal is to remove water where it should not remain, protect systems that cannot be fully drained, and keep critical heating and safety equipment ready for cold weather.

Start With the Plumbing System

The plumbing system is usually the biggest winter risk in a seasonal home. Water can remain trapped in pipe dips, fixture valves, supply lines, water heaters, filters, toilets, and appliance pumps.

Depending on the home’s plumbing layout and equipment, professional winterization may include:

• Shutting off the main water supply
• Turning off the well pump or municipal water feed
• Opening faucets to relieve pressure
• Draining the water heater, pressure tanks, and treatment equipment
• Protecting traps, toilets, and appliances with non-toxic RV/plumbing antifreeze

Gravity draining alone is often not enough. Horizontal runs, fixture valves, check valves, appliance connections, low spots, and changes in piping elevation can all retain water. Properly regulated compressed air can help clear those areas when the system is designed and handled correctly.

Do Not Forget Wells, Filters, and Water Treatment

Many seasonal homes in New Hampshire rely on private wells. A drilled well may use a submersible pump located well below grade, but that does not mean the rest of the water system is protected from freezing.

Areas that may still need winterization include:

• Above-ground piping
• Pressure tanks
• Jet pumps
• Water filters
• Softeners, neutralizers, and backwashing filters

Water treatment systems can be especially easy to overlook. Putting a system in bypass does not necessarily remove the water trapped inside it. Softeners, filters, UV systems, and other equipment should be winterized according to the manufacturer’s procedure or by a qualified water-treatment or plumbing professional.

Appliances, Toilets, and Traps Hold Water Too

Washing machines, dishwashers, ice makers, and some refrigerators can hold water in small internal valves, pumps, hoses, and drain lines. These components should be winterized according to the appliance manufacturer’s instructions. Depending on the appliance, that may involve draining internal parts or using non-toxic RV/plumbing antifreeze where specified.

Even after water lines are drained, traps still need protection. Sink traps, tub drains, shower drains, floor drains, and toilet bowls all hold water to block sewer gases.

Water left in traps or fixtures can freeze and damage components. Traps that dry out can also lose the water seal that normally blocks sewer gases.

Use only non-toxic RV/plumbing antifreeze in approved areas. Never use automotive antifreeze in plumbing fixtures, drains, or septic systems.

Heating Systems Need a Different Plan

Some seasonal homes are fully shut down for winter. Others stay heated at a low temperature to protect finishes, plumbing, and mechanical systems.

Domestic plumbing and a closed-loop hydronic heating system are two different systems and should not be treated the same way during winterization.

If the home uses a hot water boiler, the heating system may need glycol protection. Glycol can help protect pipes and boiler components during a power outage or heating failure, but it must be mixed, tested, and maintained correctly.

Too little glycol may not protect the system. Too much glycol can reduce heating efficiency and strain circulator pumps. If a hydronic system contains glycol, the fluid should be checked for freeze protection, condition, concentration, and pH. The heating system should also be inspected for proper pressure, leaks, circulation, and overall operation before winter.

If the Home Will Stay Heated, Add Remote Monitoring

Seasonal homes that remain heated have a different risk: the house may be fine until a boiler, furnace, heat pump, fuel supply, or electrical service fails.

If plumbing remains pressurized, consider a low-temperature alarm, remote thermostat, water-leak sensor, or monitored freeze alarm. These devices do not replace proper winterization, but they can alert someone to falling indoor temperatures or a leak before an unattended problem becomes major property damage.

Just make sure someone can actually respond to the property if an alert occurs.

Mini-Splits, Propane, and Fuel Systems Need Winter Access

Ductless mini-splits are common in New Hampshire homes, including seasonal properties. Their outdoor units need room to breathe during winter. Snow and ice can block airflow, interfere with defrost cycles, and damage the outdoor unit.

Mini-split outdoor units should sit high enough above expected snow buildup and should be protected from falling roof snow, icicles, and runoff. Do not shut off power to a mini-split for an extended winter period without checking the manufacturer’s instructions.

Propane and fuel systems also need winter access. Before closing the home, make sure:

• Propane tanks and regulators are marked and accessible
• Delivery drivers have a clear path
• Vents, intakes, and exhaust terminations are clear of snow risk
• Heating oil levels are adequate for expected winter operation
• Tanks, fill pipes, vents, and fuel lines show no obvious leaks or damage

Snow or ice blocking a combustion-air intake or exhaust vent can interfere with appliance operation and may create a carbon monoxide hazard.

Septic Systems Need Winter Protection Too

A septic system is easy to forget because it is underground, but freezing can still happen. The soil and snow above the system act as insulation. Driving, parking, snowmobiling, or heavy foot traffic over the septic area can compact the snow and soil, reducing that insulating effect.

For seasonal homes, avoid traffic over the septic tank, main line, and leach field. If a system is new, shallow, or exposed, a loose layer of straw or mulch may help insulate it before the ground freezes.

Never pour automotive antifreeze, rock salt, harsh chemicals, or drain-clearing chemicals into a septic system to prevent freezing. These products can damage the bacteria that make the system work and may create bigger problems in the spring.

Waterfront Homes Have Extra Winter Responsibilities

Lakefront homes often have docks, boathouses, or shoreline structures that need winter protection. However, New Hampshire has specific rules for devices that prevent ice from forming around shoreline structures.

As of August 4, 2026, state law limits the use of de-icing or agitating devices to what is necessary to protect legally existing permanent structures adjacent to the shoreline from ice damage. Devices operating on public waters must also be registered with the local municipal clerk, and required DANGER, THIN ICE warning signs must be posted.

The device cannot interfere with ice access from neighboring property. Homeowners should review RSA 270:33-34 and current local requirements before installing or operating a de-icer.

A Simple Seasonal Home Winterization Checklist

Every property is different, so this list is a planning checklist rather than a universal winterization procedure.

Before leaving a New Hampshire seasonal home for winter, make sure these areas are addressed:

• Main water supply shut off
• Well pump or water feed turned off
• Water heater and pressure tanks drained
• Plumbing lines professionally drained or blown out where appropriate
• Water treatment systems winterized according to manufacturer guidance
• Toilets, traps, and appliances protected with non-toxic RV/plumbing antifreeze
• Boiler system checked if the home remains heated
• Remote temperature or leak monitoring considered if systems remain active
• Mini-split outdoor unit clear of snow and ice risk
• Propane, oil, vents, regulators, and septic areas checked

When to Call a Professional

Winterizing a seasonal home is not one single task. It is a coordinated process involving plumbing, heating, water treatment, wells, appliances, fuel systems, and sometimes septic or waterfront equipment.

Professional winterization is especially valuable when a property has multiple heating zones, a private well, water treatment equipment, hydronic heat, finished spaces over unheated areas, complex appliance connections, or plumbing that cannot be completely gravity-drained.

A missed valve, trapped line, forgotten filter housing, or unprotected appliance can create thousands of dollars in damage. For New Hampshire homeowners, professional winterization gives peace of mind that the home is protected before the first hard freeze.

Al Terry Plumbing & Heating has been serving New Hampshire homes for 50 years. Our plumbing and heating team can help evaluate seasonal properties, winterize vulnerable plumbing and mechanical systems, check boilers and heating equipment, and identify areas where trapped water or freeze exposure could create problems.

Need help closing up a seasonal home before winter? Contact Al Terry Plumbing & Heating to schedule professional winterization service.