Do any of you use the pet-safe antifreeze Sierra made by Peak Anitfreeze?https://peakauto.com/products/antifreeze-coolants/automotive/sierra/
Peak Sierra pet-safe antifreeze.
- Thread starter Hayden Watson
- Start date
I'm not certain I see the value of this for a boat for a couple of reasons.
Ethylene glycol and propylene glycol have different effects on rubber and similar soft materials like engine seals, impellers, and hoses. If the seals in your engine are not resistant to propylene glycol then there could be major repairs.
Second, both are toxic, propylene glycol is just less toxic. Toxicity to animals is a concern on land because an antifreeze leak in a car leaves antifreeze on the ground and animals can ingest it. An antifreeze leak in a boat leaks into the bilge, a highly unlikely place to find the family dog. So, animals ingesting it isn't a big problem.
Both glycols break down pretty quickly in the environment to non-toxic substances. One of the resident chemists on the forum can explain more fully or a google search will yield a few articles on the subject. Additionally, if any anti-freeze gets discharged from the bilge, it is quite quickly diluted so it will not be toxic to marine life and then it will break down quickly.
Ethylene glycol and propylene glycol have different effects on rubber and similar soft materials like engine seals, impellers, and hoses. If the seals in your engine are not resistant to propylene glycol then there could be major repairs.
Second, both are toxic, propylene glycol is just less toxic. Toxicity to animals is a concern on land because an antifreeze leak in a car leaves antifreeze on the ground and animals can ingest it. An antifreeze leak in a boat leaks into the bilge, a highly unlikely place to find the family dog. So, animals ingesting it isn't a big problem.
Both glycols break down pretty quickly in the environment to non-toxic substances. One of the resident chemists on the forum can explain more fully or a google search will yield a few articles on the subject. Additionally, if any anti-freeze gets discharged from the bilge, it is quite quickly diluted so it will not be toxic to marine life and then it will break down quickly.
Thanks Dave. This is for a hydronic system that will also be heating the hot water tank so my main concern was about cross contamination of the potable water if the heat exchanger leaked.
I use ethylene glycol to winterize my diesel and holding tank. It's supposed to be less harmful to the equipment. Yeah, a little goes into the water when I run it thru the engine inflow.
Many of us have ethylene glycol in our engines and heat hot water with it. I don't think cross contamination is a big concern. The HW tank should have a check valve on the inlet side to prevent back flow from the HW tank due to expansion. This would prevent contamination. If there was contamination, it would affect the hot water system not the cold, not many of us drink hot water. The dyes in the AF would also give a clue, if the water is looking a bit red or green, you know something is up.
There are a number of PG-based coolant products being sold. Fleetguard ES Compleat (Cummins Filtration) and Starbrite are two others. Thinwater has posted extensively about them. The compelling reason for using the PG engine coolant in lieu of EG coolant - our boats circulate engine coolant into a heat exchanger in the hot water heater. I switched to Fleetguard ES a few years ago, a couple of quick fresh water flushes and changed out to Fleetguard. My engine runs a stable 170 degrees all summer long, about 5 degrees lower than with the old EG coolant.
Hopefully Thinwater will comment on this formulation.
Hopefully Thinwater will comment on this formulation.
Whup! That's me...
Ethylene glycol is what is found in "normal" antifreeze. The -OH groups on the organic molecule allow it to hydrogen bond with water thus allowing an organic molecule to be dissolved in water. This lowers the boiling point. Things that can hydrogen bond also have a very large boiling point which is why they work well in car radiators.
A funny thing about Ethylene Glycol (a.k.a. 1,2-Ethanediol) is that it is very toxic and can do severe liver damage if digested. I call it a "funny" thing because simply adding one more carbon and one more -OH group produces a molecule that is essential to good health-glycerin (a.k.a. 1,2,3-propanetriol). One will kill you and the other keeps you alive. FUNNY!
Glycerin combines with three fatty acid molecules to form triglycerides and is how the body stores energy (fat). Glycerin is also used as a food moisturizer (think 7-year shelf life for Twinkies or that moist pouch of chewing tobacco you have hidden under the seat of your car)
Now! take one -OH group off of the end of Gylcerin and you have propylene glycol (a.k.a. 1,2-propanediol). It is sort of "in between" the two extremes of "will kill you" and "must have to be healthy".
BTW: The "glycol" nomenclature indicates a molecule with TWO -OH groups side-by-side.
BTW-again: The reason we don't have glycerin based anti-freeze is that too many yeast and bacteria like critters can use it as food.
I've tested ES Complete and Startbrite engnie coolant (ASTM test methodologies) and they are both excellent products. I was a chem E in the AF business in a former life, involved in formulation.
Yes, the cross contamination issue is an interesting one. I would probably use Fleetguard ES if I had such a system.
There are multiple reasons not to use glycerine:
- First, you are only allowed a few percent glycerine in engine coolant. More than that and it is difficult (impossible?) to hit all of the freeze, boil, and viscosity specs at the same time (gylcerine is too viscus).
- Glycerine is not a glycol. a technicality, but there you have it. Because it is a byproduct of biodiesel production, there was a push to use it in AF. It failed.
- Glycerine is not a very effective antifreeze.
- Glycerine is generally more toxic and more expensive than PG (the use of glycerine on babies is restricted).
There was one other factor that caught my eye while evaluating engine coolants - the high-speed, lightweight (Yanmar and Kubota)diesels have thin piston cylinder walls that can be damaged by coolant cavitation erosion, Fleetguard ES Compleat is formulated to provide cavitation protection. Maybe we need a mechanical engineer in this conversation! 
Yanmar is pretty specific about their antifreeze, they recommend Dex cool, the GM compliant antifreeze.There was one other factor that caught my eye while evaluating engine coolants - the high-speed, lightweight (Yanmar and Kubota)diesels have thin piston cylinder walls that can be damaged by coolant cavitation erosion, Fleetguard ES Compleat is formulated to provide cavitation protection. Maybe we need a mechanical engineer in this conversation!
How stable are EG and PG? When they enter the environment what causes them to break down and what do they break down in to?
Yanmar sells their own brand, Mack-Boring has a list of AF that they have tested and recommend but note that there “may be some solutions that are acceptable but have not been tested”. What M-B doesn’t acknowledge is wet cylinder cavitation corrosion, a concern for high-load marine diesels.
http://ldmarineservice.com/files/yanmar_bulletins.pdf
Heavy duty diesel antifreeze does address cavitation erosion and there are several forumulations, commonly NOAT and OAT mixes. You can get them in EG and PG versions.
https://www.practical-sailor.com/issues/37_46/features/Coolants-that-Fight-Corrosion_11523-1.html
The one thing that Yanmar and M-B both specify is that the engine coolant be replaced yearly, something I suspect few skippers actually do.
PG is toxic? I'm pretty sure that it's still commonly used as an ingredient in rootbeer & other consumable items. I think that it is listed in both the US Pharmacopeia & the Food Chemical Codex. It's even on the FDA GRAS list (21CFR181).
I use the exact Peak Pet safe formula from the original post in our Espar with zero issues. It's good stuff, and if you get a leak it is way less toxic than other alternatives. Only issue is it's pricier.
Although Dexcool is not specifically rated for diesels and thin cylinder walls (cavitation), it has performed very well cavitation testing. In fact, this is generally true of OAT formulations, even light duty ones. Yanmar is right about it being quite suitable.
EG and PG are effectively equal both in terms of biodegradability and marine toxicity. Both are low hazard in the environment in moderate quantities. EPA and Fish and Game agree on this.
It is a continuum, and the rank order depends on the organism in question. None are carcinogenic, accumulate, or are toxic at low levels. For example:
Chemical LD 50 Rat
Ethanol 7,000 ppm
PG 22,000 ppm
EG 4,800 ppm
Glycerine 12,000 ppm
Salt 3,000 ppm
Not much, the units are off
He is trying to quantify the relative toxicity of those chemicals using a standard test method where 1/2 of lab rats died for the given dosage.