Winters can be hard on our RVs’ plumbing system, septic systems, and engines with the liquid freezing and then expanding, causing some severe damage. Luckily, you can save a lot of cash on unnecessary repairs by winterizing your RV with the right RV antifreeze, but I am sure you are wondering how the antifreeze will affect your septic system. So here is what you need to know about RV antifreeze and septic systems.

RV antifreeze is a unique non-toxic fluid that has a freezing point of -50 (or -100) degrees Fahrenheit, thus protecting your water lines in places that experience frigid winters. In warm weather, you can flush RV antifreeze down the drain or into the septic system.

An RV is a big investment and repairs from damaged systems can be very costly.  So preventing damage from frozen water lines is with RV antifreeze is important. In this article, we’ll show you how to winterize your RV and if it’s safe to pour the antifreeze down the drain.

For more anti-freeze resources, start here:

What Is in RV Antifreeze?

A bottle of Freezeproof RV antifreeze
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Freezeproof RV and Marine antifreeze

The cold winter months pose a huge threat to the system in RVs, we all know that we have to winterize them. But the automobile antifreeze won’t do the trick; in fact, it is quite toxic to any parts of an RV other than the engine.

Therefore, you must winterize your RV using the right RV antifreeze.

What is RV antifreeze and how do you find it?

RV antifreeze is a pink liquid formulated to prevent RV water systems from freezing in temperatures down to -50 (or -100) degrees Fahrenheit. It is made of ethanol or propylene glycol, is non-toxic, and is made for RV plumbing.

What Is the Difference Between Automobile Antifreeze and RV Antifreeze?

A close shot of a mechanic's hand pouring antifreeze into a vehicle's radiator.
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BanksPhotos via Canva.com

While both RV and automobile antifreeze can prevent the liquid in pipes from freezing, the difference is important.

The most important difference between RV antifreeze and automobile antifreeze is that car antifreeze is highly toxic to humans and animals.  RV antifreeze is non-toxic and made to be used in the RV water system. 

RV antifreeze features a non-toxic formula that helps prevent the plumbing pipes from expanding and bursting as the water freezes. RV antifreeze is made using biodegradable components; therefore, when accidentally spilled, it won’t affect the environment.

Remember, some of your RV’s water tanks are used to store the freshwater used to clean the RV, cook, and drink. Therefore, make sure you winterize it using non-toxic antifreeze.   

Although they perform the same function, there is a huge difference between these two types of antifreeze. But one thing that remains the same is their main ingredients. The primary components in most antifreeze products are ethylene glycol and Propylene glycol.

On an interesting note, automobile antifreeze is used in the cooling system of the engine. Therefore, the boiling point is as important as the freezing point.  RV antifreeze is not made to be boiled or heated under pressure.  So do not use the pink stuff (RV antifreeze) in your car.

Ethylene Glycol

A considerable percentage of the antifreeze products are prepared by mixing a base product like (Mono propylene glycol or mono ethylene glycol) with numerous additives and distilled water. Ethylene glycol was discovered in 1926, and since then, it has been marketed as antifreeze. And that is because its high boiling point can come in handy during the cold weather and summer months.

Even though it’s used in a wide range of systems, it can oxidize into five organic acids (acetic, glyoxylic, glycolic, oxalic, and formic acids). Ethylene glycol has a toxic effect when ingested because your liver can convert it to numerous agents that are quite toxic. In fact, about 1.4 ml/kg of ethylene glycol is lethal to a 140-pound individual if he/she is not treated within an hour of ingestion.

Propylene Glycol

Unlike ethylene glycol, propylene glycol is less toxic and has even been referred to as non-toxic antifreeze by some manufacturers. This antifreeze is used where the toxic antifreeze cannot be used like in plumbing lines and food processing systems. The FDA has allowed this chemical to be added to numerous baked goods and processed foods.

Another primary component that is used in diesel engines is the propylene glycol methyl ether.

Antifreeze Chemicals

ComponentConcentration in water (%)
Calcium Oxide32
Ethanol 50
Ethylene glycol50
Glycerol 50
methanol50
Potassium chloride11
Propylene glycol50
Sodium chloride23
sucrose42
Urea44
The chemicals in antifreese

How Do RV Water Systems Work (and How Antifreeze Affects the Process)

Even though we don’t always talk about it, the water system is a crucial aspect of your RV. And without one, you would never consider it to be traveling home. But many people refer to their RVs’ wastewater systems and plumbing as the sewer system.

Basic Components of an RV Water System

The water systems of RVs vary depending on the model and type of RV. But some of the basic components found in all systems include:

Fresh Water Holding Tank

RVs have a tank that holds water to be used for cooking and cleaning.  The water is pumped from the tank to the water heater and the faucets and toilets.

Gray Water Tank

The gray water tank is a unique holding tank that receives the water from the shower or sinks.

Just for fun, you may be wondering about peeing in an RV shower. You are in luck! Read our discussion here: Can you Pee in an RV Shower and other Graywater Questions.

Wastewater or Black Water Tank

The wastewater tank collects all the wastewater toilets only.

Note: some systems also collect water from a sink or outdoor sink that may be piped to the blackwater tank. I personally think it is a terrible design but my travel trailer is piped this way.

Dumping System

Generally, the above tanks collect all the wastewater while you’re away camping and when full, you connect them to the sewer hose and empty them into a sewer connection. The dumping system on RVs can differ, with some coming with pumps that remove the waste while others use gravity.

How Does the Antifreeze Affect the Water System?

A child filling the sink with antifreeze chemical
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Winterizing an RV with RV anti-freeze. Pouring to fill the p trap.

The ethanol or propylene glycols used to make RV antifreeze are safe and nontoxic.  So as long as you are using the pink RV antifreeze you can add it to the fresh water holding tank, pump it through the drinking water lines, and add it to the wastewater holding tanks.

When winterizing your RV, you should flush all the water from all your tanks by opening the low drain valves. Make sure you flush the toilet to ensure that all the water is flushed out.

Once it’s drained, you can cap all the valves and prepare to add the antifreeze into your water system. You should make sure the water heater is drained but bypass your RV’s water heater when filling with antifreeze. Therefore, you may need a bypass kit that some new models come with, and if you don’t have one, you should get one from a trusted mechanic.

There are three methods for pumping antifreeze into your septic system and includes:

  • With or without the bypass kit
  • Using a hand pump from the outside
  • Using the water pump from inside the RV

All you have to do from the inside is disconnect the water line and insert it in the bottle containing the antifreeze. Allow the pump to run as it pulls the antifreeze into your water system. And then run the faucets starting from the kitchen to the outdoor shower, ensuring that they turn pink before turning them off.

Can You Pour RV Antifreeze Down the Drain?

You can pour RV antifreeze, that was in the holding tanks, down the drain at your house, or into the dump station.  RV antifreeze is non-toxic. The volume of RV antifreeze used in a camper is minimal compared to the amount of water in the sewer. 

Once it is time to de-winterize your RV and get out camping, what do you do with the antifreeze that is in the system?  You will need to dump the greywater and blackwater holding tank.  Also, you will need to flush the water lines and freshwater holding tank.

Generally, I flush all the lines until I do not see any pink.  Then, I flush for a few more minutes.  However, we do not drink the water in the fresh water holding tank, so I do not worry about ingesting any leftover antifreeze.  

If you have the bottle of RV antifreeze that you used, it will generally say right on the bottle nontoxic and safe.  The bottle will also say for RV and cabin use and toilet water from a cabin washes into the sewer or septic. 

Can You Pour RV Antifreeze into a Spetic System?

What if you have a septic system for your house or cabin?  Will RV antifreeze damage the septic system?

RV antifreeze is labeled non-toxic, and the bottle will say “septic safe” if you can do this. Generally, dumping the few gallons from the RV lines and holding tanks will be adequately diluted in the septic system.

However, flushing your system with large amounts of water may damage the water balance in your septic system.  So, you should flush any freshwater (not wastewater) onto the ground or into grassy areas.

Some people report dumping the RV antifreeze directly on the ground in areas that allow this practice.

FAQs

Can I Pour RV Antifreeze on the Ground?

As a rule, dumping RV antifreeze on the ground should be avoided.  However, when RV antifreeze is labeled as non-toxic and safe, some areas allow dumping small amounts (2-4 gallons) directly on the ground. 

Although it’s not toxic, you should not pour a lot of RV antifreeze into the ground. Antifreeze is still made up of numerous chemicals and dumping a large amount of this solution can have an adverse effect on the environment.

Can I Pour the Antifreeze in My RV’s Freshwater Tank When Winterizing?

RV antifreeze is non-toxic and made especially for RV water lines.  You should pour a gallon in the RV fresh water tank to winterize it.  However, you will need to adequate flush the tank to remove the antifreeze when de-winterizing. 

The best way to winterize your water lines inside the camper is to add the antifreeze directly to the water pump. You should not pour this solution into your freshwater tank and then run it through the plumbing system. Remember, even when fully drained, some water remains at the tank’s base, reducing this solution’s protection level.

We have a guide to winterizing your RV that you need to read before the temperatures drop: A Guide To Winterizing Your RV (Temperatures And More)

Should I Pour Some Antifreeze in the Black and Gray Tanks?

Pour about 2-3 gallons of antifreeze into each of the gray and black tanks to help protect the seals and drain valves. The antifreeze can be added through the toilet and the sinks. 

Make sure to add antifreeze to every sink and drain so that the pee trap and lines fill with antifreeze.

Final Thoughts about RV Antifreeze

RV anti-freeze is specially designed with no toxic liquid to protect the water system in your RV.  This pink substance should be added to the RV system before temperatures dip and damage occurs to your RV.  When spring comes you need to know how to properly dispose of the antifreeze into the sewer or septic.  

Make sure you know how to winterize your RV properly and what temperatures will cause damage to your RV.  I panicked one night when the temperature dipped but I was not sure exactly what temperature and duration would cause problems.  I wrote all about that here.

For more anti-freeze resources, start here:

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