Antifreeze also acts as water boiling prevention in the summer, increasing the boiling point by more than 10 degrees Fahrenheit. Also, RV antifreeze gets pumped into the system and then flushed out when winter begins. RV antifreeze, on the other hand, is non-toxic and protects the water system. But (and you knew there’d be a “but” didn’t you?) You might be a little shocked, but RV antifreeze isn’t deemed to be toxic for animals. Though essential to automobiles, antifreeze is toxic to plants, animals and the environment, and should be treated and stored with great care. The inclusion of denatonium benzoate in antifreeze does not mean it is now safe for pets, wildlife, or children. Even water is toxic if you drink enough of it. While RV antifreeze is non-toxic in small, residual amounts, such as the trace amount left in the water lines, it’s still a chemical. The HSLF estimates that between 10,000 and 90,000 animals are poisoned each year after ingesting ethylene glycol in antifreeze and engine coolant. Automotive antifreeze is a whole different critter. This is because an RV antifreeze has biodegradable materials. Is RV Antifreeze Safe for Septic Systems? Is an RV antifreeze toxic to animals? Many types are toxic, and should only be put into an engine cooling system. To help protect pets, wildlife and children, the provincial government passed a regulation that requires the addition of a bittering agent to all antifreeze sold at the consumer level in British Columbia. Yes, a reliable RV antifreeze can be safely used for any type of septic tank. You’re here because you need an important question answered: If RV antifreeze is toxic to animals. Unfortunately my vet is on vacation and they referred me to the aspca Propylene ethynol used in RV antifreeze isn’t nearly as toxic to dogs and other animals as the super toxic ethylene glycol (automotive antifreeze). It is the PROPYLENE GLYCOL antifreeze and indicates that it deemed "generally safe by the food and drug administration". Yes, Automotive type antifreeze is ethylene glycol, which is sweet tasting and is metabolized in the body to many very toxic chemicals. The short answer is that a) it depends on the type of RV antifreeze, b) how much of it we’re talking here and c) what pet / animal you have.