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WTF - What To Flush

April 25, 2019

What can I flush down my RV Toilet - Flushable wipes, tampons, condoms, poop, pee, urine, rv toilet paper


  • Only allow human waste (poop and urine) and toilet paper into your black tank. No trash, plastics, flushable wipes, femenine hygiene products, etc.
  • Don’t allow food waste into your gray tank.
  • Caustic chemicals—like chlorine, bleach, alcohol, formaldehyde, and oxidizing agents—will kill off the necessary beneficial bacteria inside your holding tanks.

To Flush Or Not To Flush

If you've been RVing for any length of time, you know what you allow down your sink and toilet drains has a big impact on how well you can prevent holding tank troubles, including clogs and harsh odors. Building good holding tank habits (like being picky about what you are willing to flush) will help you avoid these frustrating and expensive problems. 

But for those who are newer to RVing, figuring out what is and isn’t safe to flush is a fairly anxiety inducing task. Not to worry. In this article, we will dive into what chemicals and products you can and can’t allow into your holding tanks.

Your RV Wastewater Systems

Your RV contains both a black water and a grey water system. These systems can be very sensitive in regard to what we put down them. And because these two wastewater systems are so sensitive, it takes some good maintenance habits to make sure to avoid black or gray water system disasters. But don’t worry, maintaining these systems and keeping them completely free of odors and clogs is actually pretty simple. 

Let's briefly go over what each of these systems does, and then cover what items should and shouldn't be allowed inside your black and gray water holding tanks.

The RV Black Water Tank

The black water holding tank is where all the human waste is stored. Your toilet leads to your black water holding tank. There are actually only a few things that should be allowed inside your RV black tank:

  1. Human feces and urine
  2. Toilet paper
  3. Water 
  4. Non-hazardous RV Holding Tank Treatments

Anything other than that can and often will cause issues. These prohibited items include:

  1. Trash
  2. Plastics
  3. Hazardous chemicals
  4. Caustic cleaners
  5. Feminine hygiene products
  6. Flushable wipes

In essence, only allowing the correct waste into your black water holding tank is the first step in avoiding black water holding tank problems.  For more information on the other steps to take when treating your black tank, check out The Unique Method — a comprehensive, proven guide for treating and maintaining  your RV black tank.

The RV Gray Water Tank

The gray water tank holds all the water from your sinks and shower. This water shouldn’t contain any human waste, simply water that is used for rinsing, showering, etc. But just like your RV black tank, there are only a few things that should be allowed inside your RV gray tank:

  1. Water 
  2. Soap
  3. Non-hazardous RV Holding Tank Treatments

Soap scum, decomposing food, and grease going down into the lines and tank from the drains are what cause odors as well as misreading level sensors inside gray tanks. It’s especially important that you do everything you can to prevent food from getting into your gray tank. This food (which causes grease) can wreak havoc on your gray tank. Here’s how it happens: As the food-contaminated water sits inside your tank (if, that is, you leave your gray tank valve closed when camping), it will deposit a thin layer of food residue and grease on the tank’s floor and sidewalls. This grease residue also coats your sensors and causes them to misread. But misreading sensors isn’t the only issue that can come from grease buildup inside the gray tank. Believe it or not, grease buildup creates immensely harsh odors. In fact, this grease buildup can even start to smell worse than the human waste odors that can creep out of your black tank!

For that very reason, water, soap, and safe holding tank treatments are the only things that you should allow to go down your sink or shower. 

As far as keeping food from getting into your gray tank, an in-drain sink strainer can easily prevent solid food waste from going down into the drain.

To break down any odor-inducing grease or waste that has already gone into your gray tank, we recommend treating your holding tank regularly with a bacteria-based treatment like RV Digest-It

Chemical Products To Avoid

It is crucial to avoid using any chemical product in your gray or black water water systems. These products will actually harm the necessary bacteria inside your tank that promotes waste breakdown and removal. If these harmful chemicals do eliminate the bacteria inside the tank, waste breakdown is halted, resulting in clogs, backups, and expensive fixes. 

The chemicals or products that will kill the beneficial bacteria inside your holding tank are:

  • Alcohols
  • Antibacterial Soap
  • Bleach
  • Chlorine
  • Formaldehyde (any aldehyde)
  • Iodine
  • Strong acids, like sulfuric acid
  • Very strong alkaline chemicals, like lye or sodium hydroxide.

These items are the most common chemicals that can disrupt your holding tank and lead to waste buildup and odors, so it’s best to avoid them altogether.

NOTE: It is also possible that any antibiotics you may be taking could negatively affect the beneficial bacteria inside your holding tanks as well.

Guide Continued Below

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What RV-Safe Products Can I Use?

If you want your holding tank to perform at its maximum potential, you should choose the right products that will keep your tanks and water systems safe. These products include safe drain cleaners, safe toilet bowl cleaners, and safe holding tank treatments. Again, using the The Unique Method will also greatly reduce your risk of any future trouble that can arise from your water systems. 

In Summary

Because RV wastewater systems can be ultra-sensitive, being aware of what is safe to put inside the tanks is crucial for avoiding odors and backups. But restricting the kinds of things you allow inside your black and gray tanks is just the beginning. It takes good daily habits and following The Unique Method to keep things running smoothly at all times. 

We hope that this guide has helped you understand what you should and shouldn't flush into your RV gray and black water holding tanks. Of course, we’re with you every step of the way! If you ever need any help or have any questions, please feel free to contact our customer support team! Happy camping!

Adopt The Unique Method

You bought your RV so you could enjoy life and spend time with family and friends. The last thing you want to do is waste precious time and money on fixing wastewater holding tank problems. Keeping your tanks in peak operating condition doesn’t have to be hard, confusing, or expensive if you follow our proven process: The Unique Method.

The Unique Method is a comprehensive tank care plan that we developed after years of conversations with real customers facing real problems. The Unique Method provides you with simple, preventative steps to stop odors, clogs, and sensor problems before they start so you can spend less time worrying about your holding tanks and more time enjoying the freedom and adventure of RVing. Try it yourself and see why thousands of campers trust their RVs with The Unique Method every day.

If you need more help with anything covered in this guide or simply have a comment, we’re here to help you anytime!

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