A common question asked by the RV community is whether you should keep your black water valve open or closed. Before we go any further, the definitive answer is:
You should always keep your RV black tank valve closed unless you’re actively dumping.
Unfortunately, if you ask a random group of RVers this question, you’ll receive mixed responses that suggest that leaving your black tank valve open is completely fine. This is dangerous and problematic, because the truth is that leaving your black water tank valve open is one of the fastest ways to develop inconvenient and messy clogs in your RV.
In this guide, we’ll provide you with all the details you need to know about how to use your RV’s black water tank valve, and how using it properly can keep your black tank free from clogs, foul odors, and misreading sensors.
Key Points About Keeping Your RV Black Water Valve Closed
- The most important thing to remember is to keep your RV black water tank valve (sewer valve) closed unless you’re actively dumping the tank, regardless of whether you’re on hookups or dry camping.
- Keeping your RV black water tank valve closed prevents clogs and pyramid plugs, supports proper waste breakdown, and reduces black tank odors.
- Keeping your black tank valve closed is the first rule of The Unique Method, an expert-backed system that was created over 30 years of solving wastewater issues professionally — providing clear, easy-to-follow instructions that will help you prevent 99% of RV wastewater problems before they even occur.
- If you mistakenly left your RV black tank valve open and you’re trying to get rid of a pyramid plug, we recommend using a high-quality, bio-enzymatic treatment like Unique Clear-It, the strongest and most effective RV black tank clogger on the market.
Keep Your RV Black Tank Valve Closed: Why it Matters
When you leave your black water tank valve open, liquid inside your holding tank drains out as expected, but toilet paper and waste are often left behind. Over time, this solid waste builds up on top of itself and can cause a pyramid plug. Poop pyramids can grow so large that they eventually prevent anything, even liquid, from entering the tank.
Many RVers don’t know that their black water holding tank is generally flat across the bottom, meaning that if solid waste is added to a tank devoid of liquid, it will simply sit on the bottom and continue to pile up in the same spot.
Caution: You may be one of the lucky campers that has left your black water tank valve open and have never experienced any issues. But after working with hundreds of RVers to address clogs, we can confidently tell you that it’s only a matter of time before your luck runs out. We strongly recommend that you change this practice while you’re still ahead!
Find out how to use your RV wastewater valves correctly with our helpful guide: The Definitive Guide to Using Your Wastewater Valves
RV Black Tank Valve Usage: Hookups vs. Dry Camping
Regardless of the type of camping you’re doing, you always need to keep your black water tank valve closed unless actively dumping. Let’s take a closer look at each camping style to learn why it’s important.
Full Hookups
You might assume that if you’re camping with hookups that you can leave your RV black tank valve open, because everything will flow directly into the sewer. Unfortunately, leaving your black tank valve open will still allow the liquid to flow out and leave waste and debris behind, causing pyramid plugs, clogs, and foul odors to develop.
Dry Camping
Keeping your RV black tank valve closed is even more important when dry camping or boondocking because open dumping (emptying any RV holding tanks directly onto the ground, in storm drains, or in national parks), is illegal in the United States.
Beyond the legal ramifications, the same consequences like pyramid plugs, clogs, and foul odors can develop if you leave your RV black tank valve open.
Learn about where to safely dump your RV holding tanks: Where to Dump Your RV Holding Tanks
What are the Benefits of Keeping Your Black Tank Valve Closed?
Keeping your RV black water tank valve closed provides you with a lot of benefits, and helps your RV’s wastewater system continue running smoothly.
1. Prevents RV Clogs & Pyramid Plugs
Pyramid plugs generally develop slowly over time as toilet paper and waste accumulate into a pyramid shape right below the RV’s toilet line.
When the black water tank valve is left open, it’s true that all of the liquid flows out as expected, but the gently-sloped bottom of the black water tank that most RV’s have, allows the waste and toilet paper to be left behind. This can be compounded if the RV is not properly leveled at each campsite.
Over time, the waste and toilet paper bind together and can stack on top of each other to form a poop pyramid. When left unchecked, the pyramid can grow so large that it blocks the pipe from the RV toilet to the black water tank, creating the pyramid plug.
By keeping your RV black tank valve closed, you can avoid dealing with trying to clear a pyramid plug while camping.
Learn more about pyramid plugs with our helpful guide: What is an RV Pyramid Plug
2. Helps RV Treatments Work Effectively
Your RV black water holding tank relies on gravity to move liquid and waste out of the tank. In order for everything to flow out of the tank effectively while dumping, you need to ensure that all of the waste and debris is as liquefied as possible.
Solid human waste and toilet paper will not break down fast enough between dumps on their own. However, two things can help speed up this process dramatically:
- Water: Water helps to soften everything inside the black tank, blocks odors by keeping waste below the waterline, and allows RV black tank treatments to reach ledges, crevices, and other areas where waste and debris often accumulate.
- High-Quality Black Tank Treatment: Waste-digesting, aerobic bacteria- and enzymes in RV black tank treatments like Unique RV Digest-It Ultra, rely on water to both survive and reach all of the waste and toilet paper they will quickly break down.
By keeping your RV black water tank closed, you allow the liquid level in the tank to rise and soften the contents, block odors, and allow the bio-enzymatic tank treatment to safely and completely digest and liquefy the waste between dumps.
3. Reduces RV Toilet Odors
Foul odors are one of the most common RV problems, and they’re usually caused by not having enough water inside your black water holding tank.
Water is the most important thing you can add to your black water holding tank because it acts as a natural odor barrier. When you keep your RV black tank valve closed, you allow the water level to rise, which helps your black tank stay clog- and odor-free.
By closing your black tank valve, water can help prevent odors in the following ways:
- Vapor Barrier: Adding water to the toilet bowl before you use it, and after every flush, acts as a vapor barrier, blocking odors from the black water tank and preventing them from reaching the rest of the RV.
- Physical Barrier: Avoid the “porta potty effect” by keeping waste and toilet paper below the water line, significantly reducing the odors wafting up from the black tank.
- Cooler Tanks: Hot tanks are the leading cause of stinky black tanks and fresh water will cool down the RV black tank, and help to eliminate odors.
Discover all the ways that water can support your RV black tank with our guide: Why Using Lots of Water in Your RV Toilet and Tanks is Crucial
How to Unclog Your RV Black Tank After Leaving Your Black Tank Valve Open
Pyramid plugs develop slowly over time as waste and toilet paper build up on top of itself.
Clearing a pyramid plug may seem frustrating, messy, and gross, but it doesn’t have to be. If you use Unique Clear-It, you can avoid an inconvenient trip to the RV service department, and unclog your RV black tank without getting your hands dirty.
For step-by-step instructions about how to deal with a pyramid plug, refer to our guide: How to Get Rid of an RV Pyramid Plug
Important Note: Pyramid plugs can often be confused with blockages in the toilet line because they share one critical symptom: water pools in the toilet bowl because the clog prevents water from reaching the black water tank.
If you aren’t sure if you’re dealing with a pyramid plug, make sure to review our guide 3 Common Types of RV Toilet Clogs You Should Know About
How to Protect Your RV Black Tank With The Unique Method
The Unique Method is a proven, science-backed, and easy-to-follow approach to treating your RV wastewater holding tanks. The core of The Unique Method is a 50/50 approach: 50% about the right process, and 50% about using the right product.
The Unique Method provides clear guidelines about how to prevent odors, clogs, and misreading sensors in your RV black water holding tank.
The Unique Method’s Rules for RV Black Tank Care
- Always keep your RV black tank valve closed, unless you’re dumping a full tank.
- Only treat your RV black holding tank with a high-quality bacteria and enzyme treatment (such as RV Digest-It Ultra).
- Keep several inches of water in your RV toilet bowl (unless driving), which creates a water barrier, preventing foul smells from seeping into your RV living space.
- Fill your RV toilet bowl with water before you use the toilet; this will help solid waste flow easily down the line, and deter any trapped odors from rising during the flush.
- Use ample amounts of water each time you flush your RV toilet. Hold down the flush mechanism for at least 10 seconds each time you flush your toilet to continually add water to your black tank.
- Try to keep your RV tank temperatures between 45-85°F [7-29°C]. When temps reach extreme highs and lows, holding tank treatments may not work as effectively. Additionally, as temperatures rise, so do odors.
- Dump your RV holding tanks every 3-5 days for optimum odor control. If you extend the time between dumps (like when dry camping/boondocking), treat your tanks every 4 days with a bacteria and enzyme treatment and keep plenty of water in your holding tank.
- Rinse your RV black tank every time you dump, by filling your tank to full capacity, and then dumping the contents. Waste collects and accumulates in the low spots and crevices of your holding tank; rinsing removes any lingering waste or toilet paper.
- Avoid cleaning your RV toilets with chemicals or bleach. Use RV toilet cleaners that will increase beneficial bacteria, like Unique Scrub-It RV toilet bowl cleaner.
- Deep clean your RV black tank twice per year with Unique Clean-It (season beginning and end for weekend campers), or every 5-10 dumps (for full-time RVers). Deep cleaning fully resets your tank to a level of cleanliness that you cannot achieve on your own.
- Never store your RV with waste in the tanks. Storing your RV with waste in the tank is the best way to create a compacted tank, making it impossible to dump. The best policy is to dump at a station on your way home, or immediately upon your return, so you don’t have to deal with a compacted tank during your next trip.
- Store your RV with a black tank full of water that is treated with Unique Store-It. Be sure to dump your tank, and rinse well before refilling it with water and adding the treatment. This will help deep clean your black water holding tank while the RV is being stored.
These simple rules will help keep your RV’s wastewater systems running smoothly year-round, allowing you to enjoy your trips without clogs, foul odors, and misreading sensors.
FAQs: Keeping Your RV Black Water Tank Valve Closed
Here we’ve put together a convenient list of some of the most frequently asked questions we receive from campers about using their RV black water tank valves.
1. Why Should I Keep The RV Black Tank Valve Closed?
It is important to keep your RV black water tank valve closed, except when actively dumping, because it protects your black water holding tank from clogs, pyramid plugs, and foul odors.
2. What Happens if I Leave the RV Black Tank Valve Open?
If you leave your RV black tank valve open, the liquid will flow out of the tank as expected, but solid waste, toilet paper, and debris will be left behind.
Over time, the waste and toilet paper can pile up on top of itself forming a pyramid plug. When a pyramid plug isn’t addressed, it can grow so large that it blocks the RV’s toilet line, preventing you from flushing anything into the black tank.
3. Can I Leave the RV Black Tank Valve Open While On Hookups?
No, even when you are on full hookups, you should always keep your RV black tank valve closed unless you’re actively dumping.
If you leave your black tank valve open while you’re connected to a sewer, clogs may develop, foul odors may rise into your RV, and sewer flies can make their way into your camper.
4. Should I Use a RV Black Tank Treatment If I Leave the Black Tank Valve Open?
No. If you try to use an RV black tank treatment while your black tank valve is open, you’ll be wasting time and money as the treatment simply drains out of the tank.
You should always leave your RV black tank valve closed. As the water level rises, it will keep the aerobic bacteria and enzymes alive, and allow them to reach the waste they need to break down inside the tank.
5. Why is Water Important in an RV Black Tank?
Water is the most important thing you can add to the black water holding tank in your RV.
It prevents pyramid plugs and compacted tanks by softening waste, it reduces odors by keeping your black water tank cooler while acting as a vapor barrier, and ensures your tank is full enough (2/3 full or more) for an effective dump.
6. Can Sewer Flies Enter an RV Through an Open Black Tank Valve?
Yes. Leaving your RV's black tank valve open will cause the liquid to drain out, leaving solid waste and toilet paper behind to dry, which attracts sewer flies by creating a breeding ground of organic matter and odor.
7. How Can I Clear an RV Pyramid Plug After Leaving My Black Tank Valve Open?
Clearing a pyramid plug may seem like a difficult task, but it can actually be very easy and straightforward with Unique Clear-It and our helpful guide: How to Remove an RV Pyramid Plug.
8. How Full Should My RV Black Tank Be Before Dumping?
For an effective dump, you should ensure that your RV black tank is 2/3 full or more prior to dumping. This ensures that there is enough liquid to flush out most of the solids without leaving debris behind.
9. Is It Ever Safe to Leave the RV Black Tank Valve Open?
No. Unless you are actively dumping your tank, you should always leave your RV black tank valve closed.
10. Are the Rules for RV Black Tank Valves and Gray Tank Valves the Same?
No, not exactly. Black tank valves should always be kept closed, and if you’re dry camping or boondocking, your gray tank valve also needs to remain closed. If you’re on hookups, you can leave your gray tank valve open.
Important Note: You should investigate the sewer at the campground before leaving your gray tank valve open, and if there is evidence of sewer flies, you’ll want to keep your gray tank valve closed to prevent them from finding their way into your RV.
Prevent Common Problems In Your Tanks!
From misreading sensors, preventing clogs, or eliminating odors, we've got you covered no matter how you camp! All our best holding tank tips and trick information plus more can be found conveniently in one place when you download our FREE Unique Method Field Guide PDF. Achieve holding tank bliss today!
Get The Free Download Get The Free Download
