November 1, 2025 – WISCONSIN
Wisconsin Lakes and the Last Wilderness Alliance are calling for urgent state action to halt the spread of Aquatic Invasive Species (AIS) via the ballast systems found in wake boats.
AIS management already costs MILLIONS of dollars annually in Wisconsin. Evidence shows that wake boats contribute to this problem by transferring invasive species between lakes.
The Problem with Ballast Systems
Studies confirm that ballast systems, which are filled with lake water to weigh down wake boats to create surfable waves, retain water and invasive species:
- A University of Wisconsin study by Campbell found that, on average, wake boat ballast systems contained 8 gallons of residual lake water after being removed from a lake. Some boats held over 22 gallons.[1]
- This residual water was found to contain AIS, including zebra mussel larvae and zooplankton. Spiny Water Fleas (zooplankton) have been found in 24 Wisconsin lakes, and no effective eradication exists.
- A University of Minnesota comparison of eight boat compartments showed that ballasted boats contained the most zebra mussel larvae. Median data indicated 296 veligers (larvae) were found in ballast systems.[2]
- Transferring a ballasted boat from an infested lake to a new lake carries a 7 in 10 chance of transferring 100 mussel larvae.
The Common-Sense Solution: Hot Water Flushing
Fortunately, a common-sense, common-ground solution to this problem is Hot Water Flushing.
Some boat manufacturers, such as Malibu [3], recommend flushing the ballast system with hot water to prevent the spread of invasive species like quagga and zebra mussels.
- Flushing the system with hot water at 120 degrees or greater kills quagga, zebra mussel juveniles, larvae, and spiny water fleas in seconds.
This procedure not only helps prevent the spread of AIS but also allows boaters to comply with existing state and federal laws prohibiting the spread of quagga and zebra mussels.
Proposed Regulation
The boating industry and lake advocates agree on this hot water flushing solution, representing a point of “common ground.” The decontamination protocol and equipment already exist.
1. All recreational boats with ballast systems must be flushed with hot water (120 degrees or greater) before being launched into a different Wisconsin lake.
2. All flushing certifications would be required annually, with a new certificate required at the start of each boating season. This annual requirement would also prevent ballast tank antifreeze [4 ]from being discharged into a lake after winter storage.
3. If a boat is used on only one lake all year, it would only require cleaning once per year.
This prevention measure is considered a reasonable, common-sense approach.
Funding the Program
The cost of this prevention program should not fall on taxpayers. Instead, the industry and wake boat owners should cover the funding. The industry should have originally designed ballasted boats to drain completely and allow easy cleaning to comply with existing state law, but it did not.
What are we waiting for? Every lake in Wisconsin should not have to become infested with quagga mussels, zebra mussels, spiny water fleas, and the next new invader before action is taken.
Call to Action:Please contact your legislators and urge them to require mandatory hot water ballast flushing for the 2026 boating season.
Please forward this message to a friend.
Protecting our lakes is worth this level of prevention.
Wisconsin Lakes is the only statewide 501 (c) (3) non-profit organization working exclusively to protect and enhance the quality of Wisconsin’s lakes. We are the citizen arm of the Wisconsin Lakes Partnership.
The Last Wilderness Alliance’s 501 (c) (4) mission is to advocate for the protection of our natural resources to support Wisconsin’s long-term environmental and economic viability.
CONTACT:
Last Wilderness Alliance: Jeff Meessmann, , 715-385-0268
Wisconsin Lakes: Ben Wojahn – Executive Director, , 608-661-4313
[1] Volume and contents of residual water in recreational watercraft ballast systems,” Management of Biological Invasions (2016) Volume 7, Issue 3: 281-286, first published online 04/18/2016, https://www.reabic.net/
[2] “Occurrence and Survival of Zebra Mussel (Dreissena polymorpha) Veliger Larvae in Residual Water Transported by Recreational Watercraft,” University of Minnesota thesis, Adam Doll, Dec. 2018, https://conservancy.umn.edu/
[3] https://drive.google.com/file/
[4] https://drive.google.com/file/
Malibu warns that zebra mussels can “attach and infest inside” ballast systems. Screenshot:
Flushing the Ballast Tank System
These procedures have been developed to help prevent the spread of aquatic invasive species, especially quagga and zebra mussels that attach and infest inside ski/wakeboard boat ballast tank systems. Flushing the system with hot water (120°F or greater) kill quagga and zebra mussel juveniles and larvae in seconds and protects water bodies from
Malibu says ballast tanks must be filled completely with very hot water to decontaminate. That is several hundred gallons. It’s not a do–it–yourself job! (Residential water heaters are only about 50 gallons)
.Fill each of these four (4) ports with hot water of at least 120°F.
- The corresponding ballast tank will completely fill with hot water and begin flowing out of the adjacent port and/or the port located on the bottom of the boat.
⚫ Allow the hot water to continually flow for 10-15 seconds before moving to the next port.
. After all four (4) locations have been successfully flushed for 10-15 seconds, the process is complete.
Screenshots from the Malibu 2024 owner’s manual, p 120-122
https://cdn.malibu
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boats.com/docs/owner-manuals/2024%20Malibu%20Owner%27s%20Manual.pdf?_ga=2.136996405.482784965.1713270232-1686420796.171327023
Winterization
Ballast tanks, pumps, hoses and fittings must be properly winterized to prevent freezing damage during winter storage. Because of the complexity of preparing a ballast system for winter storage, as well as the possibility of extreme damage to the ballast system if a preparation error is made, MasterCraft recommends scheduling an appointment with an authorized dealer’s service department to have a certified technician to perform all winterization procedures, including ballast winterization. Master Craft uses a -50 F RV type, nontoxic, propylene glycol based antifreeze to winterize every boat built at the factory. Any antifreeze meeting these requirements is acceptable for MasterCraft engine, ballast, and freshwater system winterization. Be aware that colder climates may require antifreeze with a -100 F temperature rating.
Winterization Process
- Completely empty all ballast tanks and bags of any water that may be in the ballast system.
- With all bags still hooked up to the system, identify the ballast thru–hull vents (see guide to each model in this Owner’s Manual).
- Add two gallons of -50 F RV type nontoxic propylene glycol based antifreeze to each of the thru–hull vents. Colder climates may require antifreeze with a -100 F temperature rating.
- Once the antifreeze is in all ballast zones, use the manual ballast switches in the helm area to drain the antifreeze through the system. This will push antifreeze through the ballast system, across all pumps, hoses, fittings and intake valves.
- Be cautious while using the ballast switches as antifreeze will be pumped out of the intakes mounted to the bottom of the boat. Once antifreeze begins to pump out of the boat through the 4 ballast intakes (three aft, one forward), turn the pumps off.
From p 245 at https://www.mastercraft.com/media/ywxbltjn/mastercraft_my2022_ownersmanual.pdf