December 12, 2022
How Do I Keep My Dock and Boat Free from Ice Damage in the Winter?
De-icers are an effective method of protecting your dock, boat, and boathouse during winter.
For lake or pond owners in colder climates, keeping your boat and dock in the water during the winter is an appealing option. However, water when it gets to the freezing point it is a force to be reckoned with. Below we touch on why ice can be destructive to your dock, boat, or boathouse and de-icing options and methods for mitigating the risk.
Water composition and temperature in the winter:
When water temperature decreases, water becomes denser (heavier) until it reaches 39 degrees Fahrenheit. The denser water falls to the bottom and the slightly warmer less dense water moves towards the surface. 39 degrees is the point where it completely flips. From 39 degrees to 32 degrees water becomes less dense. Cooler water rises towards the surface while warmer water falls to the bottom. At 32 degrees water density is at its lowest creating the perfect conditions to freeze, which of course is what happens at the surface.
Why ice is destructive:
As ice forms and expands it encroaches the pilings of a dock, a boat, or a boathouse, squeezing the structures. Destruction comes from what is known as “ice jacking”. Ice jacking occurs when water levels rise and fall, usually from rainfall or changes in tide. When ice forms around a structure, the surface ice layer stays at the same height as the water level lowers. When the water level rises again and freezes again, the newly formed ice layer “jacks” the surface level ice upward. Because the ice is squeezing the structure, with multiple high/low freezing water cycles, ice jacking can lift a piling from its foundation, even breaking it in half. The result can be a collapsed dock, damage to the foundation of a boathouse, or damage to a boat or lift.
De-icers: an effective solution
De-icers can be an effective option for preventing ice damage. They circulate warmer water from the bottom of a pond or lake to the surface to prevent and reduce ice formation. However, too much open ice can be detrimental as ice can break off and gain momentum slamming against pilings, boats, or boathouses – referred to as an ice floe.
De-icers provide an added benefit of helping prevent fish kill and allowing for harmful gases to release as muck decomposes at the bottom – especially important in ponds or shallow lakes. For more information on fish kill and winter aeration, check out this article: https://www.hiblow-usa.com/2020/02/27/winter-pond-aeration/
Types of de-icers
There are two major types of de-icers: agitators and bubblers. While both circulate and push water to the top, the mechanics and results can be very different. Agitators are excellent for deeper water applications particularly in marinas and channels, while bubblers can be most effective for shallow water applications at or below 6’.
Agitators are powerful rotary motors that resemble a fan or propeller. They are completely submerged in the water and thrust warmer water toward the surface to prevent ice formation, or to create a hole if ice has formed. Agitators have multiple options for mounting:
- Mooring Rope Suspension: great for deeper applications particularly in a marina
- Dock mounted: typically allows the agitator to tilt and rotate 180 degrees
- Floating Mount
- Stand: if used in shallow water
Most agitators require oil lubrication which can be problematic as they do leak sometimes. The propellers (blades) can clog from plant life or even animals causing them to break down. The agitator often creates a wide diameter hole which is beneficial for some applications but detrimental to others as ice floes can occur. They are not energy efficient and can stir up muck at the bottom causing natural habitats to be disturbed.
Bubblers (aerators) – located outside of the water in some type of enclosure – pump air through a weighted tube to diffusers that are located at or near the bottom of a pond or lake. Diffusers produce tiny bubbles that circulate warmer water to the surface creating and preventing a hole in the ice. The subsurface aeration process also increases dissolved oxygen levels which helps prevent fish kill and speeds up the decomposition of organic matter (muck) that settles to the bottom. The aeration process is especially helpful for ponds and shallow lakes and typically used throughout all seasons.
While agitators are proficient in deeper water, bubblers are perfect for shallow water up to 6 feet. Multiple diffusers can be placed in the water in parallel with the dock which allows for greater linear coverage, yet less open ice, making ice floe less of a threat. There are 2 standard types of bubblers:
- Rocking Piston: Dual head rocking piston pumps are also used for deeper water pond and lake aeration (10-50’) and handle higher pressure well. Models range all the way up to 3/4 HP running on over 600 watts at about 70 decibels.
- Linear Diaphragm Air Pump: HIBLOW air pumps are most prevalent for shallow water aeration up to 10’, although for use as a bubbler, we suggest up to 6’ max depth to maximize air flow. HIBLOW aerators typically produce more air flow than rocking pistons in shallow water but can’t handle the higher pressure (10’+) as well. The pumps run oil and lubrication free, are energy efficient with most models running on 75 watts or less. Noise levels are between 32-45 dBa depending on the model. They are built to run 24/7, 365 and are very easy to maintain.
HIBLOW invented the linear diaphragm air pump in 1968. Considered to be a premium aerator, HIBLOW air pumps handle pressure better than competitors. Longevity and ease of repair allow for years and years of continuous operation. Give us a call or email to assist with pump sizing and diffuser quantity and type. 734-944-5032. firstname.lastname@example.org
Final thoughts/ tips:
- If choosing a bubbler and you are concerned with fish health, HIBLOW recommends keeping the diffuser(s) off the bottom by 2-3’ especially if you are de-icing a pond or small lake. This will allow your fish to find refuge in warmer water at the bottom, but also provide enough circulation to keep a hole in the ice
- A medium or coarse bubble diffuser is recommended for de-icing. Check out our article on diffusers to learn why. https://www.hiblow-usa.com/2021/05/03/pond-aeration-system-diffuser-options/
- Place the diffusers in a direction where the air flows in parallel with the dock
- Professionals recommend keeping the ice open just enough so it doesn’t touch your structures. Monitor the lake or pond and put a timer on your agitator or bubbler if needed. Typically, bubblers can run 24/7 because they are less powerful and require far less energy
- Check your local laws about de-icing. Some areas have laws and restrictions on how much you can de-ice
- It is always good to check with your neighbors to make sure they do not have issues with the de-icing process
- Add a sign on the waterfront to warn folks of not walking on the water to help prevent any liability claims. Many counties require this
- If choosing a bubbler, keep the air pump in an enclosure with as much air circulation as possible. Inside a boathouse or shed is perfect. A HIBLOW can stand alone outside as well, but it is best to keep it in the shade for maximum life
Author: Mike Miner
For more education content on pond aeration, check out the following articles:
- Winter pond aeration
- DIY solar pond aeration
- Fall pond aeration
- How to calculate back-pressure in a pond aeration system
- Increasing your aeration system’s longevity
- Tube sizing
- Diffuser selection
December 12, 2022