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Urine Is Not Water - Using Water In Your Holding Tank

March 03, 2020

Urine is not water - Using Water in Your Holding Tank vs. Thinking Urine is Enough

Key Points:

  • Although it contains water, urine and water are not interchangeable 
  • It is crucial to use water in your holding tank to avoid odors and backups that can come from simply using urine alone in your holding tank.

At first glance, it seems logical: if you need plenty of water in your RV’s holding tank to help facilitate the breakdown of waste and control odors, then plenty of urine ought to do the same thing, right? Actually, not so much. There are many reasons why urine is simply not a good substitute for water in your holding tank and in this guide we are going to explore why urine is not a good substitute for water in maintaining your black water holding tank. 

Chemical Differences

Most people who think that urine is an adequate substitute for water are actually thinking somewhat logically. After all, urine contains water, so why can’t you just use urine instead of wasting precious water to fill up your holding tank? Well, the big thing is while urine does contain water, it is not just water. While it's true that 91-96% of urine is made up of water, the composition of the other 4-9% completely changes its ability to be used as an effective liquid in a holding tank.

One of the substances that makes up that 4-9% is uric acid. Uric acid, or urea, is a waste product created during the digestion of food. Urea is often expelled in the form of sweat, but it is also a major component of urine. Urea is a by-product of protein breakdown and is often broken down one step further into ammonia. Ammonia is where the majority of those nasty urine smells come from!

Beyond this, while urine is generally sterile, it can in some cases contain bacteria. In fact, according to Summit Medical Group, it is possible to have some bacteria in your urine and still be perfectly healthy

When you combine ammonia with even trace amounts of bacteria, you’d better be ready for smells in your RV’s holding tank!

Urine Odors

With the chemical differences in mind, it’s easy to see why urine smells a whole lot worse than water. Moreover, when urine is allowed to metabolize inside your holding tank—combining with the bacteria in solid waste—it begins to smell even worse! Because of that 4-9% that is not water, urine can be quite a smelly substance! On this fact alone, if RV holding tank odor control is your goal, urine is not your answer!

How Much Liquid Do You Need to Use?

Beyond odors, however, there are some more practical things to consider if you’re contemplating substituting urine for water. A fundamental aspect of Unique’s proven holding tank treatment program—The Unique Method—is that you must use enough water to completely cover the solid waste in your tank. Covering solid waste with water creates a barrier between it and you, preventing odors from seeping up into your RV. 

The simple  fact is that you will not physically have enough urine to completely cover the solid waste in your holding tank, unless, of course, you’re downing several gallons of water per day (not a practical or healthy idea).We  recommend, instead, holding down your flush pedal for at least 10 seconds every time you use your RV’s toilet. That’s a whole lot of water in that ten seconds, significantly more than multiple humans could produce in urine in one day. In the end, substituting urine for water in your holding tank just isn’t practical from a production standpoint.  

Diminishing the Effectiveness of Holding Tank Treatments

Let’s assume, on the other hand, that you simply want to skip adding additional water to your tank altogether. In other words, you already know that water addition outweighs urine production, but in the end you just don’t want to “waste” water by adding it to your tank. Even in this case, you’re likely setting yourself up for disaster.

A  key step in The Unique Method is to add a high-quality, bacterial-based RV holding tank treatment to your holding tank. The bacteria in this product needs plenty of water to hydrate them in order for them to properly break down and digest the waste. If you use only urine (i.e., you simply choose not to add additional water), then the bacteria won’t have enough liquid in which to thrive. Without adequate water, these bacteria will not be able to most effectively break down waste. Not only that, but if the urine inside your tank does not completely cover the solid waste, the bacteria won’t even be able to get to the solid waste to break it down!

Fundamentally, if you use urine as a substitute for water, you’re essentially causing your high-quality holding tank treatment to work less effectively! And if the product can’t do its job, you’ve set yourself up for future failure. 

Guide Continued Below

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Problems Dumping / Pyramid Plugs

If you substitute urine for water, one key issue that you will likely face in the future is problems dumping your tank. The Unique Method recommends that you dump your tanks every 3-5 days for optimum odor control. If, however, there is not enough liquid in your tank, you will almost inevitably encounter clogs and backups when you go to dump your tank. Likely, you will discover a pyramid plug (a literal pyramid of feces that builds up inside your holding tank). A pyramid plug is the result of inadequate liquid and/or inadequate or ineffective bacteria colonies in your tank.

It Rolls Down Hill

Ultimately, if you use urine as a substitute for water, you will have inadequate liquid in your tank, which will impact the effectiveness of the bacteria-based holding tank treatment, which will cause a pyramid plug, which often makes dumping your black tank a real hassle. In short, it isn’t worth it!


While it seems logical to save water by using urine in your holding tank instead, we now know that this isn’t really a great alternative. Simply put, urine is inferior to water. By using plenty of water in your holding tank, it will help prevent odors, cause the bacteria in your high-quality holding tank treatment to thrive, and make it way easier for you when it comes time to dump your tank. As always, we understand this is a complicated topic and would love to answer any additional questions or concerns you may have. Even if you just have a comment, please feel free to reach out to us. We would love to help you! 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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