Dilute and Flush
Flushing used antifreeze down the drain is the least-preferred disposal option, but it may be the only option available in some areas. Your wastewater treatment facility should be contacted to ensure that they can accept the waste prior to using this method.
Although antifreeze is biodegradable, households on septic systems should NOT dispose of antifreeze down the drain. If your home is connected to a septic tank, give this product to someone who is connected to a municipal sewer system. Even in a diluted form, antifreeze can overwhelm and destroy the bacterial action in your septic system and drain field.
Provide adequate ventilation by opening windows and doors and/or turning on a room fan.
Carefully pour about 1 gallon of diluted antifreeze down the sink, flushing with large amounts of water. Failure to dilute antifreeze may damage pipes or other parts of your plumbing.
Continue disposing in 1 gallon batches until completely gone. Don't mix products, and wait several hours between disposing of different types of products.
The best time to do this is during the working day when the sewage system is in full use so that this material passes through the municipal sewage system faster.
These procedures are intended for small quantities of used antifreeze from a household only.