Dumping and Maintaining Wastewater Tanks

Dumping and maintaining Casita gray and black waste water holding tanks isn’t the most glamorous topic we might discuss, but it certainly is an important topic for most who are new to Casita Life.

Some new to Casita Life decide to order their new Casita as a standard model, sans bathroom, to save on trailer weight, gain extra living and storage space, or because they don’t want to deal with dumping a black water tank. Others elect to order a deluxe model Casita with an onboard bathroom, that provides a marine-style toilet with black water waste holding tank. Having camped with and without an onboard marine toilet over 45 years, Dorrie and I long ago decided an on board toilet is essential equipment. And, its utility has increased as we have become senior campers.

Most RV hard shell campers and even some pop up campers today have marine-style toilets. Marine toilets aren’t like house toilets. Because there’s no toilet water tank, you need to do a two-step flush: Push the handle or pedal halfway down to fill the marine toilet bowl with water, then push it down all the way to flush into the black water holding tank.

It’s very important to do both flush steps, letting the toilet fill with water, so there’s enough water to break down solids as it splashes down into the black water tank. Bypassing the first flush step will impede waste breakdown and lead to a buildup of clumpy solids in your holding tank, and probably result in solid wastes not fully clearing out of the tank when dumped.

Most RV campers have two types of waste water holding tanks on board: a gray water tank, and a black water tank, if the trailer has a marine toilet. The gray water tank holds waste water that drains from the RV kitchen and bathroom sinks and shower drain. It is the presence of soap residue and dirt that give this waste its name and gray-ish look. The black water tank holds waste only from the marine-style RV toilet. It’s called a black water tank because … well, let’s just say, it’s called that for obvious reasons.

The black water tank holds both liquids and solids. In addition to human waste, it collects water used to flush the toilet, and of course, toilet paper. You should always use toilet paper designed for use in RVs. This toilet paper breaks down and dissolves in holding tank chemicals, preventing potential problems with the holding tank, the RV sewer system and the dump station septic system.

One golden rule for RV holding tanks is to never dump the black water tank until it is at least two thirds full. You want the tank nearly full so the weight of the water will force its contents to drain properly. If possible, don’t dump the black water tank more than once every few days to a week — longer intervals mean the toilet chemical has more time to break down solids.

The second golden rule is never throw anything into your toilet other than RV toilet paper. It won’t break down in your holding tank and will damage or clog your dump pipe and/or dump valve, creating a nasty mess you won’t want to clean up. Be sure to use RV toilet paper, which dissolves much quicker. Also, use it sparingly. The less solid waste that needs to dissolve, the better.

Use non-abrasive cleaners in you sinks - and dish soaps and hand soaps and etc - that are kind to the environment and they will be kind to your black/gray water tanks. Don’t put caustic cleaners and products - especially products like drano - down your drains.

The third golden rule is to never leave the black tank valve open at the campground and expect the toilet to drain or flush like the toilet in your home. It won't work.

Using More Water in Your Toilet is the Best Black Tank Odor and Dump Pipe Clog Deterrent

Water is your best friend when it comes to pooping in an RV toilet because it is a natural odor barrier and will soften the solid waste to the point where it won’t build up to create clogs. Some people who dry camp/boondock for long periods of time may tell you not to use too much water in order to conserve space in your tank and avoid dumping partway through the trip, but doing this could lead to clogs, odors, or both, another thing you don’t want partway through your trip. 

Here are key tips that will help prevent odors and clogs.

1. Fill your toilet bowl with water before you begin using it.

   When you use your camper toilet, you should fill your toilet bowl with a couple of inches of water before you use it. Doing so helps the waste to not cling to the sides of the bowl and smoothly flow down the pipe when you flush the toilet. Failing to do so can lead to clogs in the line.

2. Always keep some water the toilet bowl (unless driving).

   Constantly having at least a couple of inches of water in your toilet bowl will act as a natural barrier to odors; they will not be able to rise up from the tank through the toilet line because the water in the bowl will block it. It’s the same reason why your home toilet automatically refills the bowl with a certain amount of water after it is flushed.

3. Flush for a few seconds to add water into the black tank.

   In addition to ensuring the waste will flow smoothly down the dump tube when dumping, using plenty of water also hydrates the good enzyme acting bacteria in your tank, and keeps the solids in your tank covered with water to suppress odors.

4. Keep your black tank valve closed at all times (unless actively dumping a full tank).

   Keeping your black tank closed traps the liquids inside your holding tank, preventing any waste from solidifying or building up into a pyramid plug. Keeping water above the solid waste helps to keep odors contained under the waterline.

5. Flush only urine, feces, RV/Marine type toilet paper, and high-quality tank treatments down the toilet.

   Your black water holding tank is designed to only hold human waste and RV (dissolvable) toilet paper. Flushing any other solid items like flushable wipes, feminine products, paper towels, and other items that are not designed to break down quickly will lead to clogs and potentially costly problems.

6. Do not use too much toilet paper.

   Using too much toilet paper can cause backups and clogs in both the toilet line and the tank itself, so be sure to use only the amount you need. Some RVers also claim that you MUST use RV toilet paper in order to avoid clogs; generally toilet paper is designed to break down quickly in water. You can test your favorite household toilet paper for use in your RV/Marine toilet by sealing a few sheets of toilet paper in a mason jar three-quarters full of water and shaking it for 20-30 seconds. If the toilet paper dissolves it’s OK to use you your RV toilet.

7. Treat your holding tank with a high-quality enzyme / bacteria based holding tank treatment.

   I consider enzyme-based holding treatments the gold standard when it comes to choosing tank care products. It will ensure that the waste in your tanks stays liquefied, allowing for better flow when dumping. Even on short camping trips, adding a high-quality bacteria-based treatment can help your camping experience and your dumping experience feel like a breeze. An enzyme treatment keeps the interior floor and walls of the black tank clean and free from slime buildup. Adding a good enzyme based RV toilet chemical aids in odor control and it helps to dissolve (digest) black water tank contents — waste and tissue — into a slurry. At dump time, the black water tank slurry is more easily dumped. And when you dump just before hitting the road, its good to have water and enzyme conditioner in the tank to slosh around to clean the tank.

Cultivate these toilet / black tank routines while camping and you should easily be able to avoid many of the odor and clog issues other campers complain about. Water is the most immediate way to curb potential clog and odor problems.

If it's time to leave the campground and your holding tanks aren't full enough to dump, flush water down the toilet and run water down the sinks to fill them at least two-thirds full.

(Never use your drinking water hose for holding tank maintenance or cleaning purposes. RV drinking hoses are normally white. Take a different color hose for other uses so you can distinguish the difference.)

Make sure you have the required sewer hose, and hose couplings and connectors. I recommend you only use heavy duty sewer hoses. They're not that expensive and they hold up much better. Do not pull or drag the sewer hose on the ground. This will cause it to tear or get pin holes in it.

To hook up the sewer tube, first make sure both dump valves are closed and remove the sewer cap. Next, connect the sewer tube by putting the tube adapter over the trailer dump outlet and turn it clockwise until it locks securely in place. Take the other end of the hose over to the campground site or dump station sewer connection.

Use the necessary adapters to make the connection and get a good seal. It's a good idea to place some weight over the hose so it doesn't jump back out when you drain the tanks. It may be necessary to use some type of sewer hose support to get a good angle from the RV to the campground sewer connection so the tanks drain properly when you dump them. The small valve is for the gray water tank and the large valve is for the black water tank.

For a single dump I usually just stick the end of the sewer tube at least four or five inches deep into the site or dump station sewer pipe and secure it in place with the sewer pipe flip cover lid, if available. (I carry a box of latex gloves to use for handling the sewer tube and elbow connector.)

When we park at a campsite for an extended stay, long enough that we must dump two or more times, I thread our elbow sewer connector into the site sewer pipe to connect the sewer tube. I just leave it connected until the final dump. And for those extend stays, I usually set up my sewer tube support cradle, that looks like a giant centipede, too.

Always dump the black water tank first, followed by the gray tank. It is important to remember to ALWAYS empty your black water tank first. Once the black water tank is done emptying, I often fill the bowl with water and depress the flush valve two or three times. You can then close the black water tank valve, or leave it open while dumping the gray water tank. Dump the gray water tank by opening the (smaller) gray water tank valve. The reason you empty the black water tank first is so that soapy water coming from the gray water tank, can flush out waste left in the hose from emptying the black water tank. Be sure to close both dump valves when the tanks are empty and before disconnecting the sewer tube. (Older Casita models do not have a common waste dump connection for black and gray tank valves. Older models have a separate garden hose connection at the gray water tank dump valve. )

The first thing you should do after dumping the black water tank, before adding an enzyme conditioner, or anything else, is to add enough water to cover the bottom of the tank, so there is a good base of water in the tank. Two or three toilet bowls full should be enough for Casita toilets. Be sure to add the proper amount of enzyme / bacteria type holding tank conditioner. 

Repeat this procedure every time you dump the black water holding tank. 

To clean the inside of the black tank you can buy a spray wand or stick to clean the inside of your black water tank. Several versions of the spray wand are availabile at Camping World and on Amazon. All versions of the spray wand have a high pressure sprayer head on one end and a garden hose attachment at the other end. To use it, open up the marine toilet flush valve, insert the wand down into the black water tank, and turn on the water. The inside of the tank is cleaned by turning and twisting the sprayer head all around the tank. Once this is done, dump the tank as normal.

Another old timer’s trick to clean the black water tank before you park your trailer in the storage lot at end of season is to clean it with a mixture of water softener and laundry detergent. Fill the black water tank two-thirds full with water. Next, mix two cups of Calgon water softener with one cup of laundry detergent in a gallon of hot water and pour it down the toilet. Water softener and detergent makes any solid waste clinging to the inside of the tank release. (Some old timers advocate adding a pint of chlorine bleach to the cleaning mixture.) Let the tank set for a day before taking a short drive around town to slosh the mixture around in the tank. Then drain and throughly rinse the waste tanks as usual to winterize your trailer for the season. Alternatively, on your last camping day of the season, pour the water softer and detergent mixture down the toilet as you set up your trailer at the campsite, use the toilet normally until it is full, and then dump normally as you prepare to leave the campground.

All those black water tank cleaning options work to varying degrees, but in my opinion, the best way to clean the black (and gray) water tank is to use a natural probiotic / enzyme bacteria type tank treatment for RV, marine, camping, portable toilets. The microorganisms literally digest all the organics in the tank and that built up on tank walls. If you ever open your dump valve and nothing happens because the dump plumbing is blocked by a big clog of organics (paper and other stuff), a couple of ounces of enzyme additive will liquify the blockage clump in a day or two. I use TankTechsRx RV Holding Tank Treatment & Cleaner. (Amazon)

We have a removable screen trap in the kitchen sink drain to make sure only soapy water and no solids - not even bread crumbs - drain into the gray water tank. Even so, over time, grease and residue can build up in the gray tank and cause a foul odor, not to mention how it is affecting the tank and valve assembly. Periodically I also treat the gray tank with environmentally safe chemicals as described above to eliminate the risk of odors. You can also annually clean the gray water tank as described above for the black water tank.

While there is toilet paper that’s specifically made and marketed for use in RVs, many people wonder whether or not it’s really necessary. Toilet paper that is made for RV or marine use is designed to reliably break down (dissolve) in water much faster than toilet papers designed for use in your household. Some regular household toilet papers can wind up sitting in the bottom of a RV black tank, holding odor and attracting flies and other insects down the vent pipe. This is not what you want going on in your RV.

That isn’t all that can happen with the wrong toilet paper. If wads of intact TP become lodged in the dump tube, it can cause a backup and prevent the waste from moving into the septic system efficiently.

First and foremost, toilet paper for any RV should disintegrate quickly. Look for statements such as “Safe for RV Use,” “RV/Marine Toilet Tissue” or “Safe for Septic Systems.” If it's safe for your septic system, it will be safe for your RV.

The important thing is to find a product that is readily water soluble. You can test your favorite household toilet paper brand to see if it’s acceptable for use on the road in your RV. Fill a jar with water and put a couple of sheets of your favorite brand of toilet paper inside, then put the lid on and shake it. If the TP starts to dissolve after a few seconds of vigorous shaking, it should be fine for RV use.

Following these simple holding tank tips can prevent problems and provide you with long lasting trouble free holding tanks.

• Always dump the black water first then the gray water second.
• Allow black water tank to be at least two-thirds full before dumping. The weight and gravity will force the contents of the tank to drain properly. If you must dump before you are two-thirds full, add enough water to be sure you are at least two-thirds full.
• Always flush in 3 to 5 bowls of water with RV toilet chemical after dumping.
• Never dump anywhere but an approved dumping station.
• When hooked to a site with sewer connections always keep tanks closed until ready to dump. Never leave them open while camping. Gravity is needed to wash waste down.
• Put on latex gloves
• Remove sewer hose from carrier
• Remove the round sewer cap on trailer dump connection and connect the sewer hose by turning counterclockwise, locking the end levers over the termination end.
• Place the other end of the hose into the refuse disposal hole in the ground. Use a rock on hose to hold it down and not slip out when stuff comes rushing out. Do this before releasing sewage valves.
• Pull black water sewage handle directly toward you to its full extension.
• Wait until sewer fully drains. Do not close valve yet.
• Now pull open the gray water valve directly toward you to its full extension, releasing all waste from the trailers gray water tank.This will help wash out the hoses.
• Wait until fully drained and then close the gray water valve first by pushing it in to its original locked position. Next close the black water valve the same way.
• Disconnect the detachable sewer hose and place cover cap on the dump outlet.
• Rinse the hose and put it back in the storage compartment and put the cap back on. Use the available hose at the dumping station to rinse and never use your drinking water hose.
• Dispose of gloves.
• Wash and clean around the dump station.
• Flush approximately three to five bowls of water and toilet chemical deodorant/breakdown agent approved for RV use to black holding tank. If someone is waiting behind you at the dump station, move your trailer out of the way before doing this step.
• Wash your hands thoroughly and use an alcohol wipe for car door handle and steering wheel if you touched anything in or around the vehicle.

Additional Notes:

• Never put facial tissues, paper towels, sanitary products (including those labeled flushable) in the toilet.
• Never use detergents or bleach in the toilet. Use a sewage tank deodorizer specifically for RV use.
• Never use automotive antifreeze, ammonia, alcohols, or acetones in toilet.
• Never put grease from cooking, table scraps or other solids that may cause clogging into toilet.
• Always use a biodegradable toilet tissue specifically manufactured for RV use.Amazon