One of the most common questions we hear is: What’s the best way to clean RV holding tanks? Keeping your black and gray tanks clean and free from buildup is an important part of RV maintenance, and can help prevent the clogs, odors, and other tank problems that can quickly put a damper on your camping plans.
Over time, waste, residue, and other buildup can settle into the crevices and low points of your holding tanks, where a routine dump may not completely remove it. That’s why periodic deep cleaning should be part of your RV maintenance routine.
The best part? Deep cleaning your RV tanks is surprisingly simple. With the right methods, you can remove stubborn buildup, reduce odors, and help keep your holding tanks cleaner and better functioning throughout the camping season.
Important Note: If you suspect you’re dealing with a clog in your RV toilet or holding tanks, then this guide will not help you remedy the problem. For camper toilet clogs, please refer to our guide: Clearing RV Toilet Clogs and How to Prevent Clogs in Your Black Water Holding Tank
Key Points About Cleaning RV Holding Tanks
- Black water tanks should be deep cleaned and deodorized at least twice a year to maintain proper functionality.
- Gray water tanks should be deep cleaned at least twice a year regardless of whether you prefer full hook-ups or dry camping. If you are a full timer, we recommend deep cleaning the gray tank at least once a quarter.
- Deep cleaning RV black and gray water holding tanks is easy, inexpensive, and can be taken care of overnight while you sleep.
- Popular techniques and homemade treatments circulating online and throughout the RV community are not the most effective or safe.
How to Deep Clean an RV Black Water Tank
Regularly cleaning your black water tank is important because keeping the holding tanks free from build-up is key to avoiding clogs and foul odors in your RV. These issues can arise if waste is allowed to linger in crevices, tank ledges, sensor probes, and low points in your tanks.
Deep cleaning RV black water tanks is simple and straightforward, making regular maintenance easy to perform.
Supplies you need to deep clean your black water tank:
- Water
- Bacteria- and enzyme-based cleaner (Unique Clean-It)
- Time
There is a reason why Clean-It is the best selling black tank deep cleaner on the market! It is the strongest, most effective tank cleaner in the industry, it’s safe to use in all RVs and motorhomes, and is 100% satisfaction guaranteed.
When you use Clean-It, you are essentially hitting a “reset” button on your black water tank for a fraction of the price. Professional tank jetting services can be a hassle and are costly, while Clean-It is extremely convenient, affordable, and just as effective.
1. Close your black tank valve.
You should always keep your black tank valve closed unless you’re actively dumping.
Keeping your RV black water tank valve closed prevents clogs and pyramid plugs, supports proper waste breakdown, and reduces black tank odors.
Learn more about proper valve usage with our guide: Why You Should Keep Your RV Black Water Valve Closed
2. Fill your black tank completely full with water.
You will know the tank is full when you start to see water backing up the pipe that connects the toilet to the black tank.
Filling the tank as much as possible is essential because cleaning only occurs where water is touching. Find out why water is the best thing you can add to your holding tanks: Why Using Lots of Water in Your RV Toilet and Holding Tanks is Crucial
3. Dump one entire bottle of Unique Clean-It into your 40-gallon black tank and let sit for 12-72 hours.
Add Clean-It to your black tank by pouring it down your RV toilet.
While Clean-It can usually effectively clean and deodorize your tank in approximately 12 hours —- the longer you let it work, the better.
Important Note: No amount of Clean-It is too much, and you can feel free to let it sit for days, weeks, or months, as it will not do any damage to your RV. In fact, the more time you give Clean-It to work, the greater your results will be.
4. Open your black tank valve and dump your tank.
If you’re new to dumping or have questions about how to use an RV dump station, refer to our guides: How to Dump Your Black and Gray Water Tanks and How to Use an RV Dumping Station
5. Rinse your black tank thoroughly.
The most effective way to rinse your black tank is to fill it completely with clean water, and then dump the contents. Repeat this 1-2 times to thoroughly rinse your black tank.
Pro Tip: You should rinse your black tank after every dump, because after dumping, waste and debris can often linger in crevices, tank ledges, sensor probes, and low points. As the remaining waste accumulates, it can lead to foul odors, clogs, and misreading sensors.
6. Close your black tank valve.
Always keep your black tank valve closed unless you’re dumping!
RV Black Tank Cleaning Schedule
We recommend performing a deep clean on your black tank twice per year: once at the beginning of the RVing season and once at the end, or every 5-10 dumps for full-time RVers.
If your RV is stationary and rarely moves, it's a good idea to perform a deep clean like this every 60 days since waste tends to accumulate because it never, or only rarely, sloshes around.
Full-Time RVers: Modified Black Tank Cleaning
If you are a full-time RVer, we know that cleaning black water tanks can be tricky when you are trying to use the tanks at the same time. We recommend that full-time campers should clean their black water tanks every 10 dumps with Unique Clean-It.
Maintaining this cleaning schedule will ensure that the holding tanks work properly and will keep odors at bay.
Modified steps for deep cleaning a full-time RV black water tank:
- Dump your black water tank.
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Rinse your black water tank thoroughly to remove as much waste as possible.
The most effective way to rinse your black tank is to fill it completely with clean water, and then dump the contents. Repeat this 1-2 times to thoroughly rinse your black tank.
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Add one bottle of Clean-It per black tank.
Once you’ve added the Clean-It, you can continue regularly using your toilet. Ideally, you should let the solution work for 5-7 days prior to dumping, if possible. The more time you give Clean-It to work, the better your results will be.
The best option is always to deep clean without using the tanks, but deep cleaning while using them will still help prevent buildup and other tank issues. Just a friendly reminder, Clean-It can only work in areas where water is touching, so tank walls that are not submerged will not be cleaned.
- Dump your black water tank.
- Rinse your tank thoroughly following rinsing guidelines.
- CLOSE YOUR BLACK TANK VALVE (always keep closed unless you’re- dumping).
For thorough details about black water tank care for full-time RVers, refer to Full-Time RVing: The Definitive Guide to Treating Your Tank.
How to Deep Clean an RV Gray Water Tank
When it comes to RV odors, the black tank gets most of the attention. But your gray tank can be a strong source of unpleasant smells, too — especially when you consider the smells that can rise from your RV’s kitchen sink and shower drains.
As things like soap scum, food grease, lotions, or human hair build up, your gray or galley tank(s) can quickly become the source of unwanted odors.
Pro Tip: To prevent solid waste from getting into your gray/galley tank(s), we recommend that you use a sink or drain strainer to catch residual food waste and other debris. Ideally, you should also remove grease and food scraps from dishes before washing whenever possible.
Deep cleaning RV gray water tanks is very easy, which should make sticking to a regular cleaning schedule relatively painless.
Supplies you need to deep clean your gray water tank:
- Water
- Grease-eating dish soap (Dawn Ultra)
- Time
Through years of experience with our customers, we’ve found that the best product for removing gray tank grease and residue is Dawn Ultra dish soap. It may seem counterintuitive to add more soap to a gray tank that is already coated in soap scum and grease, but it is an incredible grease-eater that doesn’t leave a layer of residue behind like other soaps.
1. Close your gray tank valve.
2. Fill your gray tank completely with fresh water and 20 ounces (or more) of Dawn Ultra dish soap.
While the sink is running, begin by pouring 20 or more ounces of Dawn Ultra dish soap down the drain. This will help ensure that the Dawn flows beyond the p-trap under the sink and into the gray tank.
Once the Dawn Ultra dish soap has been added, continue running the sink while monitoring the lower drain that feeds into the gray tank (typically the shower drain). You will know the tank is full, or nearly full, when you see soap suds backing up the drain pipe.
Filling the tank as much as possible is essential because cleaning only occurs where water is touching. If you are attempting to restore your gray tank sensors, be sure that water covers the highest (“full”) sensor in your gray tank.
Important Note: There is no amount of Dawn Ultra that is too much. You may see the soap foaming back out of your sink or shower lines — an indication you’ve poured enough Dawn into the tank —- which is a good sign. This lets you know that the grease-eating dish soap is actively spreading throughout your RV’s pipes and cleaning out all the built-up residue.
3. Allow Dawn Ultra to sit in the gray tank, p-trap, and lines overnight.
4. Open your gray tank valve and empty the tank.
When emptying your tank, it is very common to see grayish-white residue on the bottom of your holding tank discharge pipe. This is the grease that was previously clinging to the inside walls of your holding tank.
5. Rinse your gray tank thoroughly.
The most effective way to rinse your gray tank is to fill it completely with clean water, and then dump the contents. Repeat this 1-2 times to thoroughly rinse your gray tank.
6. Repeat these steps if necessary.
Unlike deep cleaning your black tank where time is magic, there is no benefit to leaving Dawn Ultra in your gray tank for long periods of time.
The magic of Dawn is repeat cleaning, so you may need to repeat this process a few times to achieve the desired results if your tank is especially dirty. Sometimes it can take several deep cleanings before the gray tank is spotless inside.
RV Gray Tank Cleaning Schedule
Similar to black water RV tanks, it’s a good idea to deep clean your gray tanks on a regular schedule based on the kind of camping you’re typically doing:
- Hookup Campers: If you are primarily a hookup camper (and you follow our advice about gray tank valves), we recommend deep cleaning your gray tank twice a year, once at the beginning of the season and once at the end.
- Dry Campers/Boondockers: If you are a boondocker (dry camper), we recommend you perform a deep clean like this on the last night of every camping trip to avoid grease buildup inside your gray tank.
Routine cleaning of both your black and gray/galley tanks will help you stay on top of any waste and grease buildup that can cause your tanks to smell or your sensors to misread. If you need help restoring your tank sensors, refer to our guide: How to Clean and Restore RV Wastewater Sensors.
Deep Cleaning RV Black/Gray Water Combo Tanks
Determining the right way to deep clean RV combo tanks can be confusing because you may be uncertain about what to do when using them as both a gray and black water tank.
Here are a few tips about how to clean your combo tank based on your usage:
- Using a combo tank as only a black water tank, refer to the steps provided in our RV Black Tank Cleaning Guide above.
- Using a combo tank as only a gray water tank, refer to the steps provided in our RV Gray Tank Cleaning Guide above.
- Using a combo tank for gray and black water, start by cleaning it as if it were solely used as a black water tank. If you think there may be excessive amounts of grease or soap scum that were not removed with the black tank cleaning method, then follow the gray water tank cleaning steps as well.
Cleaning combo tanks can be straightforward as long as you make sure to clean them based on your usage. If you’re ever unsure, start by using the black water tank cleaning method and then follow with the gray water tank cleaning method afterwards. Utilizing both deep cleaning procedures is completely fine, and can only help clean your combo tank more thoroughly.
Call in the Experts: Hire a Professional Tank Cleaning Service
It’s very common for waste to accumulate in even the most well-maintained tanks. You may be doing everything right by using high-quality tank treatment and following the recommended maintenance procedures, but your RV holding tanks still need periodic deep cleaning.
Professional tank cleaning services are an excellent way to reset your tanks and ensure that your holding tanks are spotless. These companies use pressure washers and specialized cleaning attachments to remove waste, toilet paper, grease, and other buildup that may have accumulated during the camping season.
While professional tank cleaning can be a little pricey (ranging anywhere from $175-$400), it is an excellent option for RVers who want total peace of mind. Remove the guesswork, and check out our preferred cleaning partner: Tank Rangers RV Tank Cleaning
When Should You Deep Clean Your RV Holding Tanks?
We recommended performing a deep clean at the start and close of the camping season. That means both when you take your RV out of storage, and when you prepare to winterize. This might seem like overkill, but we have found that doing a deep clean at the beginning and end of the camping season is the most consistent way to prevent problems.
Sometimes problems can also arise during the camping season that might warrant a deep cleaning. Look for:
- Foul odors rising from the black tank while flushing the toilet.
- Misreading sensors on the black tank controller.
- Visible waste and toilet paper build up inside the black tank.
Remember, deep cleaning your RV holding tanks is simple, easy, and can often be done overnight while you sleep. If you notice any of these warning signs, don’t wait for the problem to get worse — go ahead and give your tanks a deep clean.
Cleaning Advice from the RV Community
The RVing community is great about sharing best practices and tips about how to get the most out of every camping trip. However, in terms of proper maintenance and deep cleaning of RV gray and black water tanks, the advice can sometimes be less than helpful, or even completely inaccurate.
Before taking deep cleaning advice from other RVers, we suggest that you read our article outlining Common RV Holding Tank Myths Debunked. This information will save you wasted time and effort on deep cleaning methods that simply don’t get the job done.
RV Holding Tank Care & The Unique Method
For proven and tested RV deep cleaning guidance, The Unique Method is the only thing you need to solve 99% of your RV wastewater problems.
Created over 30 years of professional wastewater problem solving, The Unique Method ensures that you will have properly functioning holding tanks for years to come. There are no gimmicks involved, all you need to do is follow the clear set of rules and use the right products. It’s that simple!
Keep Your RV Black and Gray Tanks Clean and Fresh
Cleaning and deodorizing your RV holding tanks doesn’t have to be a complicated process. Regularly cleaning the RV black tank and gray tank, using plenty of water, and addressing buildup before it becomes a bigger problem can help keep your holding tanks functioning properly and reduce unpleasant odors.
Remember, the black tank isn’t the only source of RV holding tank odors. While black tank smells tend to get the most attention, the gray tank can also develop strong odors from food particles, grease, soap residue, and other buildup. Giving both tanks the care they need is an important part of keeping your RV fresh and your next camping trip more enjoyable.
Unique Camping + Marine has been helping RVers navigate their toughest wastewater problems for over 30 years and we want to help you! So if you have any questions, contact us — we have in-house Certified RV Techs and wastewater experts for this exact reason, to help RVers!
