One of the greatest benefits to having your own recreational vehicle, be it called a coach, motor home, 5th wheel, a camper, or simply an RV, is the privacy, convenience, and cleanliness of having your own bathroom facilities wherever travels take you. Having an onboard “loo” is considered a luxury by many when it comes to journeying the highways and seeing the great outdoors.
With this nicety, however, comes the inevitable requirement of cleaning, upkeep and maintenance. And just like a septic tank at a home, an RV holding tank requires regular attention and cannot just be neglected. You, and no one else on board either, wants an outing affected by a clog, an unkept holding tank or the undeniable odor of sewage within the cabin, so it’s important to know how to care for one.
Before we go into how to clean however, let’s first understand the ins-and-outs of your rec vehicle toilet system, then we can better understand how to best take care of it.
RV Holding Tank Basics | The Blackwater Tank System
The term “RV holding tank” is most often used to mean the blackwater tank, sometimes simply called the black tank. It is also known as an onboard sewage tank and waste management system as it’s designed to do one thing only: accept the water, human waste, and paper that flushes down the RV’s toilet. The black tank then holds this sewage water until it’s time to be disposed of properly, often at an RV dumping site.
The blackwater tank as used in motorhomes, pull behinds and even tiny houses, is usually a rectangular box that is fairly simple in design. They are often made from strong, long lasting modern materials such as high density polyethylene plastic.
Storage volume capabilities for these tanks can range from as small as 4 gallons to as large as 150 gallons. For insight, water weighs 8.34 pounds per gallon (and sewage will weigh more due to solid materials). With this, a 50 gallon blackwater tank would weigh around 400 pounds when full; a hefty sum of additional weight for a vehicle.
Most RV holding tanks only have a few ports and fittings. They have the inlet port that connects to the bottom or neck of your toilet and an outlet port that connects to the discharge hose when it’s time for emptying. They may also have open/close valves for use during cleaning and dumping.
Many blackwater tanks are fitted with sensors that will tell you how full the tank is getting. These can be a common problem for RVers as they frequently get dirty or covered by septic tank contents. This can result in false readings and is a reason why a proper cleaning is needed every so often.
Why Clean a RV Holding Tank
In case you need some extra motivation, here are some reasons why the blackwater tank in your recreational vehicle should be regularly cleaned and properly maintained.
- Reason 1: Regular proper cleaning prevents the accumulation of any solids that can clog the tank, your plumbing, or dirty the black tank sensors and cause false readings.
- Reason 2: Lack of maintenance can cause you to transport extra weight from fluid/sewage in the black tank. The extra weight can lead to potentially significant issues like dislodging of a well-used tank, resulting in costly damages and repairs. It can also cause other problems such as affect drivability and fuel economy. Bottom line: discharge and/or clean your holding tank prior to travel.
- Reason 3: A favorite motto: less problem now, less work now or more problem later, more work later.
Now that we know about our RV holding tank and why it should be cleaned, let’s look at the best recommendations on how to clean it.
How to Properly Clean Your RV Holding Tank in 6 Steps
The steps to cleaning your RV holding tank will be much the same and regardless of your model or style of motorhome, 5th wheel, etc. In this RV Tanks Series post, we provide a step-by-step outline on how to properly clean your RV holding tank in 6 steps:
Step 1
Know when it is the right time to drain and clean your holding tank. When the blackwater tank is between 1/2 to 2/3 full (50%-75%) is the best time to drain. Draining the black tank at 50% to 75% will actually help the tank to drain better without leaving behind much solid waste.
To know how full an RV holding tank is, either:
- Use your RV’s built in black tank sensors (if present and operational).
- Use a dedicated measuring tool/stick to gauge tank fullness directly from the toilet.
- Make an educated guess based on how much the toilet’s been used, ensuring it doesn’t get too full.
- Simply go on the safe side and drain and clean the tank to start fresh, perhaps this time with working sensors.
Knowing when it’s time to clean your tank is less exact. If sensors are misreading, it’s a great indicator that it’s probably a good time to clean. When your holding tank/toilet is being regularly used, it may need draining/cleaning once a week.
Before storing or winterizing an RV, draining and cleaning the holding tank should always be done.
The overall idea is to keep the tank and system working optimally, with minimal odors, and before a problem arises.
Step 2
Drain the RV holding tank. When it’s time to drain the black tank, take your RV to the approved dumping location, then securely connect the end of the sewer drain hose to the holding tank outlet and open the valve.
Using a clear hose connector, elbow, or sight glass is helpful as you can visually see when the final amount of fluid has drained from the holding tank.
Many times, not all of the sewage in the blackwater tank is released on the first drain. Filling the black tank up again with clean water than draining it a second time can help to break up and flush out remaining sewage.
Step 3
Clean and flush the tank. Cleaning time means it’s time for a holding tank rinse and flush. Here we will divide into three separate sections based on whether or not you have (1) a flush valve, or similar device, (2) a factory installed rinsing system, or (3) a rinsing wand.
In all cases, we recommend the use of a clear hose connector for the sewer pipe. This simple accessory allows you to see the water as it drains and monitor it for its level of cleanliness.
Flushing is recommended to continue until rinsing produces clear, running water.
(1) Blackwater Tank with Flush Valve – Some tanks have a pre-installed flush valve. If your tank doesn’t have one, various types can be purchased. Some require permanent installation while others simply attach to the tank drain during use and can be removed when finished.
Most flush valves work to rinse the tank to break up and remove solid materials that didn’t drain. Most are fairly straightforward to use, only requiring a water supply and garden style hose. Connect the hose to the flush valve device, rinse and drain and rinse until water drains clear.
(2) Tank with Built-In Rinse Device – Some recreational vehicles feature a manufacturer installed rinsing device built into the blackwater tank. These devices are designed to perform cleaning flushes for you. Operation may vary and an instruction manual should have accompanied RV purchase and is the best option for verifying use.
(3) Tank Rinsing Wand – A tank rinsing wand is an RV holding tank product designed for this purpose, sometimes called a toilet wand. There are many models available and can be very successful in power washing inside the holding tank to clean and remove stuck-on solids.
Flexible wands with manual shut offs are the most recommended.
Use the power rinsing wand and a water supply hose, (never use your potable water hose for anything else), insert into the tank through the toilet and wash until the water drains clear.
Note on Step 3) This how-to guide recommends the use of a flush valve device due to their simplicity, cost effectiveness, and minimalized effort afforded by the technology. Many types exist from attachment styles that lock on for use and can be removed when done, to permanent installations that require relatively simple tank drilling.
Step 4
Step 4 is an RV Pro Tip. Following your tank flush and/or interior power washing via a wand or other method, flush your gray water tank. Flushing the gray water tank afterwards will help to rinse and clean the sewer hose you just got done using. You don’t want any sewage solids remaining in your lines, and flushing your gray tank after the black tank helps with this.
Step 5
Final check and clean up. Ensure all equipment has been cleaned and properly stored away for next use. Dispose of any disposable gloves. Wash hands and any clothing if splashed by blackwater.
By this point in the process, your RV holding tank should be drained, rinsed, flushed, and ready to be primed for use until the next you need to clean it.
Step 6
Prime and pretreat the holding tank for use and for the next time cleaning is needed.
If your blackwater tank is new or empty from a successful drain and clean, always prime the tank for use by adding at least one (1) gallon of water prior to any use. Some recommendations are to add enough water to fill 10% of the holding tank. If you have a 50 gallon black tank, this would mean add 5 gallons of water. This provides a stock water supply similar to the water in your toilet that helps keep solids from sticking and helps reduce odors.
It is often recommended to add some type of blackwater treatment chemical at this step also, but it is not required. There are many tank chemicals and additives on the market advertised for pretreatment and many are effective.
In this guide, we recommend the use of enzyme treatments. Enzymes aid in the digestive breakdown of waste and paper materials until the next draining. This in turn makes the tank easier to clean and promotes healthy upkeep of your blackwater tank.
Remember and note, RVing is a privilege and dump sites are provided for your convenience. Do your best to be environmentally considerate. Some chemicals should never end up in a dump site or be released to nature. There are many environmentally safe, nontoxic and/or natural products available that are more than effective and recommended by many, with us included.
Further Considerations Concerning RV Holding Tanks
- Always use bathroom tissue labeled for septic tanks or recreational vehicles. Single ply, fragrance and additive free paper that is quick to break down is the only type that should be used.
- Never put anything inside a holding tank unless you want a troublesome clog. Nothing other than quick-degrading tissue, your own human wastes, water and your holding tank maintenance additives should ever end up in your blackwater tank.
- Same goes for gray water tanks. Nothing other than water and soap residues should go down the drain to the gray tank. The outlet valve can be as small as 1/2 inch in diameter. This size is small enough that a single simple pea could cause a clog.
- Sometimes an RV holding tank, either black or gray water, may need to be replaced. This can be due to years of use from rough, avid campers or worst case, abuse from lack of maintenance. Thankfully, manufacturers provide replacement holding tanks designed for the majority of recreational vehicles that can be modified and fitted as needed. We offer a full line of RV holding tanks in a wide range of storage volumes.
Takeaway | How to Clean a RV Holding Tank
Correct maintenance of an RV holding tank is a requirement of being a responsible owner of a travel-bound rec vehicle. Your very own RV is just that – your own RV. So, using and cleaning the blackwater holding tank is your responsibility and yours alone if you want a healthy, non-odorous toilet system in your rec vehicle.
Thankfully, modern tools as well as knowing and having a set procedure in place can turn this fairly unpleasant job into a streamlined, rewarding job of RV home care. Ending up with a well-functioning and odorless camper blackwater tank is not an action of chance, but one of care and following the right steps.
We hope our how-to article has helped shed some light on the workings and use of your blackwater tank. If looking for RV holding tanks as a replacement or for other uses, we offer them here.
If you have any questions, comments or concerns, we would love to hear from you. All the best and as always – happy RVing!
