The (Cold) Case of the Frozen Antifreeze

Posted by Darrell Nicholson at 01:13AM - Comments: (3)

February 3, 2014

Pink Uni-Gard antifreeze vs. polar vortex chill: Who wins this round?

There’s nothing like buying several $3 bottles of antifreeze to protect your $30,000 boat, then coming home to discover the unused bottles frozen solid in your garage.

The blistering cold brought on by the polar vortex earlier last month elicited several queries about the effectiveness of certain anti-freeze concoctions. Among the snowbound sailors wishing he were someplace warm was Mark Baldwin, owner of a Seasprite 34, Ella, in Blue Hill, Maine. Mark sent us pictures of this Uni-Gard pink antifreeze (rated for -50 degrees) frozen solid, at -14 degrees. He was worried about what might happen to his boat’s plumbing and engine cooling system, which had been winterized using the same pink stuff.

It just so happened that when Mark’s query arrived, we were in the middle of testing various antifreeze formulas for their effectiveness. Uni-Gard pink antifreeze, which sells for about $3 a gallon at Lowe’s hardware stores and some marine chandlers, is one of the most common propylene-glycol formulas sold to boaters.

Although we have not yet analyzed the chemical composition of Uni-Gard pink, it is listed as having 25- to 35-percent propylene glycol, which should provide the -50-degree burst protection claimed on the bottle. Although it will technically “freeze” at temperatures as warm as 8 degrees, it should still be fairly soft and slushy at much lower temperatures, too soft to burst a pipe or hose.

If, however, there is a lot of water still left in the boat’s plumbing lines, the protection against freezing is diminished, and the anti-freeze can become even less effective through each freeze-and-thaw cycle. Ideally, during the winterizing process, the anti-freeze is flushed through the system to remove standing water from any low spots.

Protecting engines presents different challenges. As I pointed out in an earlier blog on this topic, propylene glycol—the non-toxic antifreeze commonly sold to RV and boat owners—is not our first choice for protecting an engine’s cooling system. In our testing, ethylene glycol, the highly toxic (when ingested) anti-freeze that propylene glycol replaced, is far less harmful to certain plastic, rubber, and nylon components in engine and plumbing lines.

Propylene glycol can harm components in freshwater and wastewater plumbing systems as well, but because ethylene glycol is not a safe choice for potable systems, there are no other antifreeze choices, other than draining the system. Some sailors have suggested using Vodka as an antifreeze for potable water systems, an approach that sounds expensive to us, but we will be testing.

For those concerned about marine toxicity, an Environmental Protection Agency (EPA) study of chemicals used in airline de-icing operations found in its tests that neither glycol formula was particularly toxic to aquatic life. However, the EPA also cited several ways in which glycol can indirectly harm aquatic life by raising oxygen levels, etc. In our view, both formulas need to be used with care on land and near the water, and disposed of properly. Ideally, all glycols should be flushed and purged so that they can be captured for recycling.

So far, our research into the various anti-freeze additives on the market is still in the preliminary stages, but PS tester Drew Frye did pass on these initial findings.

  • Never use ethylene glycol, which is highly toxic to humans, in potable water systems. The best practice is to drain the water tanks and lines of all water. When this is not possible, drain the tank and circulate propylene glycol only through the plumbing to ensure all low spots have been purged of water, then leave propylene glycol in plumbing through the winter. You should avoid adding glycol to the water tank or hot-water tank, as the glycol can attract biological growth.
  • Never use winterizing propylene glycol in the cooling system of a glycol-cooled engine. Diesel engine coolants are specially designed to prevent corrosion in the cooling system. Using a winterizing propylene glycol as an engine coolant can lead to internal pitting of the metal cooling jackets.
  • Some antifreeze formulas aimed at the RV market have ethyl alcohol in them that can damage PVC plumbing hoses. The ethyl alcohol can also cause sanitation hoses to lose their ability to prevent odors from escaping into the boat. Look for products with no ethyl alcohol.


Comments (3)

Also with a Sea Sprite 34 in Maine, I have normally emptied my potable water, hot water, and holding tanks, then pumped propylene glycol thru those systems, but used ethylene glycol in the raw water and exhaust systems. This year, I used PG in both, and have also worried about the unusually low temperatures. I've read Dow Chemical's Glycol's book (page 9 at, as Dow make both types of glycol, and feel much more comfortable that my systems will survive this winter.

HOWEVER, I finally found the Material Safety Data Sheet for the "pink" antifreeze sold by Walmart- less than 2% PG, less than 13% ethanol, less than 2% methanol, and less than 2% of butyl cellosolve- I don't think the last two chemicals should be in a potable water system! I'll look at labels more closely this Fall..



Posted by: Al Voskian | February 5, 2014 3:36 PM    Report this comment

i understand that ozone can damage some materials... perhaps gaskets, hoses, fabrics, foam cushions, ... it is very toxic at high levels and even a momentary exposure can cause harm to humans... ergo the need if used to turn off without entering the environment (pull the plug) and ventilate... -------- (several references) While ozone exposure is useful to "knock out" some smoke odor, if not used VERY carefully, it can cause rapid deterioration and oxidation of fabrics. This damage is real and irreversible! Anything with an organic structure (like textiles, carpets, furniture, books, and paper) can be severely and irreversibly damaged by ozone causing loss of aesthetic value.

The problem is that the concentration of ozone (measured in parts per million) combined with the elapsed exposure time, must be carefully monitored to achieve effective treatment without inflicting more damage from the ozone. Ozone is toxic in small amounts. Treatment with ozone should be used as a last ditch effort, when all else has failed and administered only by qualified personnel capable of monitoring the procedure very closely. --------- In addition to human and animal health, excess ozone can damage the following materials:

carpets, especially synthetic carpets; carpet padding; foam cushions; other plastic furnishings and furniture covers; rubber pads and padding; electrical wire coatings; and fabrics and art containing certain dyes or pigments.

From Ozone Generator Hazards - InterNACHI

Posted by: Windhorse | February 5, 2014 12:54 PM    Report this comment

To rid a boat of all orders, buy an ozone machine for $300. Share it with a friend or the whole yacht club. My 1984 caliber 28 had devastating mold and head odors. The sole was totally water logged. This boat had been left in a boat yard unattended for three years. After putting the machine in a closed boat for 3 days, I had a new smelling boat except for the fresh smell of new Fiberglas. Used car dealers use these devices. My unit was USA made by Jenesco located in New Hampshire.


Posted by: Georgia W | February 5, 2014 11:08 AM    Report this comment

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