Winter is upon us and ice is forming across lakes. So now is a great time to talk about dock de-icers or aquatherms (never heard of an aquatherm? Neither had we. That is what marine patrol calls them). While the use of de-icers/aquatherms is common practice to protect permanent docks and boathouses, improper use can cause damage to the structure that needs protecting and the surrounding lake ecosystem. Poor use of de-icers/aquatherms can also lead to dangerous conditions and safety risks for winter recreators.

Types of De-Icers / AquaTherms

Not all de-icers are built or operate the same, but these two standard styles are meant to keep ice from building up around or seizing to docks and boathouses that remain in the water for the winter season.

Agitators: This device works fully submerged in the water, and then circulates water towards the surface to prevent ice from forming. Agitators should be operated with a timer or thermostat controls to operate safely, and limit the amount of open water created. This device should also be maintained regularly to ensure that the lubricating oil does not leak into the water through failed seals.

Bubblers: This device releases small air bubbles from a perforated hose attached to an air compressor. The compressor needs to be located in close proximity with a power source, either on the dock or inside a boathouse. Bubblers are less likely to cause hazardous thin ice conditions and do not stir up the lake bottom.

De-icers can be expensive to operate. Both styles of de-icers, when operated properly, only need to be on for a few hours a day which accomplishes their purpose and saves energy.

Knowing the Risks

While installing either style of de-icer may prevent minor ice damage, there are possible negative impacts to operating these devices. Here are a few things to consider:

• De-icers do not guarantee less ice damage!
• If operated improperly de-icers can open up too large an area, allowing for ice flows to pick up speed in windy conditions, causing greater structure damage.
• Thin ice caused by de-icers can be hazardous or completely prohibit winter recreation activities.
• Open water at the shoreline can alter light and temperature, negatively impacting aquatic flora and fauna.
• Agitators stir up the sediments, releasing sequestered nutrients that feed aquatic plant growth including algae and cyanobacteria.
• Circulator de-icers are noisy and ruin the tranquility and stillness of winter.

Resources and Tips for Safe and effective operation of De-icers

• Register your de-icer (aquatherm) with the state as required. This is done through your local town clerk with an associated cost of .50￠ For Wolfeboro residents click here
• Hang DANGER THIN ICE signs as required by law. Specifications for signs are listed in the state regulations below.
• Choose the smallest size device for your needs.
• Only run device for 2-4 hours a day
• Only use device when temperature is below freezing.
• If using an agitator position it vertically rather than at an angle.

State Regulations

NH RSA270:33  Heating, Agitating, or Other Devices in Public Waters; Safety Hazard. No person shall put, place, operate, or cause to be put, placed, or operated in the waters of this state any so-called heating, agitating, or other device which inhibits or prevents the natural freezing of water, or forming of ice, and thereby impedes either the ingress or egress to or from the ice from any property other than that of the owner of the device. The person or persons responsible for the placement of the device shall ensure that warning signs are posted to warn of its location. Said signs shall read DANGER, THIN ICE and shall be of sufficient size to be readable at a distance of not less than 150 feet, and shall be visible from all directions and shall be equipped with reflectors and color-coded in a pattern unique for this purpose.

270:34 Registration Required.  Any person operating or hereinafter operating any such agitating or heating device which tends to inhibit the natural production of ice on public waters must obtain a registration to be designed and distributed by the department of safety, from the municipal clerk of the town in which such device shall be operated and said registration shall contain the name and address of owner and the location of said device. A permanent file of such registrations shall be kept by municipal clerks and a fee of $.50 per registration may be charged.

Looking Ahead

When the time comes to rebuild or replace your dock, consider a style of dock that can be fully removed from the water to eliminate the need for a de-icer entirely. This will save you worry about dock damage in winter, eliminate registration requirements and help preserve water quality. As more people use de-icers lakes become more dangerous for winter recreation. Limiting or eliminating their their use increases lake accessibility during the winter.