How to Drain and Maintain Your RV Holding Tanks
Properly draining and maintaining your RV holding tanks will keep them clog and odor free. Here are the tips and tricks gathered by seasoned RV owners and full-time RV residents.
The Most Important Tips for Maintaining Your RV Holding Tanks
Tip 1: When hooked up, think carefully before the leaving drains open
When connected to a site with full hookups, leave the black tank drain valve closed until two thirds full, then dump them. Here’s why:
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- If you have your tanks set to continuously drain, the solids will partially dry and form a hard pile which is hard to remove. Solids will collect and stick to every depression in your “stinky slinky” too.
- Low water flow will cause toilet paper and other solids to collect and stick to surfaces and eventually clog the drain and your tank level sensors.
- The tank additives that reduce odors and digest solids don’t work if they are flushed right out of the tank. They need fluids to do their work.
Gray tank open or closed?
- You can let your gray tank drain freely, but close the drain and let the tank fill before dumping the black tank so it gives your stinky slinky a good gush of rinse water. However, some folks report that this allows a lot of sewer gasses, and even critters, to enter the RV. Then they suggest making a water trap in the drain hose to prevent that, but leaving standing sewer water in your drain hose is not a good idea either.
- Keeping the gray tank drain valve closed solves all of that, but open it before doing laundry so it doesn’t accidentally overflow. See more detailed instructions on this website: RV Travel.
Tip 2: Don’t put toilet paper down the toilet
Regular store-bought toilet paper is a major cause of clogs in RV holding tanks. My wife suggests putting the paper in a covered wastebasket like the one shown here.
This trash can measures 6.6″W x 14.2″D x 13.3″H – 25″ so it should fit in a camper. The lid can be opened with the foot pedal.
This covered waste can uses regular grocery store bags as liners so there’s no need to by expensive plastic bags to keep it sanitary.
It should go without saying, but do not flush paper towels, sanitary napkins, anything else that does not dissolve like medicated wipes, and cooking grease.
What goes in an RV toilet?
Opinions about how to use and/or what goes into your black tank run the gamut from, “Don’t put anything but liquids down the toilet,” to “Why do you have a toilet if you’re not going to use it?”
Your views are influenced by your experiences with clogs. I don’t like clearing a poop pyramid or toilet paper remains so my wife and I just don’t poop in the RV’s potty. There’s usually a convenient bathroom, outhouse, or bush to use for the solids.
In the unusual event that there is no facility nearby, we have occasionally used the Ozark Trail Toilet Waste Bags from Walmart. They seal shut securely and go out with the trash.
Use only recommended toilet tissue in your RV holding tanks
If you are going to be putting your toilet paper in the tank, use a quick-dissolving toilet paper made for RV tanks.
Thetford RV/Marine Toilet Tissue is formulated to rapidly dissolve in sanitation systems.
Meticulously designed by RVers and boaters who have experienced wastewater problems firsthand.
Tip 3: Use the best aerobic RV holding tank additive
Unique RV Digest-It infuses a blend of naturally-occurring aerobic bacteria into your tank to replace the anaerobic bacteria and quench the foul odors. It does this by breaking down the solid waste inside your tank while giving off only water and carbon dioxide. Unique’s proprietary blend of safe, eco-friendly bacteria is much more concentrated than competitors’ brands, and outperforms competitors’ products by breaking down waste faster, eliminating odors better, and leaving behind no residue in your tanks to clog lines, foul up sensors, or degrade seals.
Stopping your RV black holding tank stink
Odors from your holding tank get nasty when you’re not using enough water, the tanks get too warm, you’re using counter-productive treatment products, or your ventilation system is not working properly.
Aerobic bacteria (the non smelly bacteria) that can really digest the stinky solids, needs an oxygen-rich atmosphere and plenty of water to work. Anaerobic bacteria doesn’t need either, and emits the smelly hydrogen sulfide gas as it breaks down waste. The Unique, RV Digest-It is aerobic bacteria. Adding it to your tanks will crowd out the smelly bacteria while doing a better job of digesting solids and toilet paper.
Whichever additive/deodorizer you use, make sure to add enough water to cover the bottom of the holding tank. Feel free to use two or three times the recommended amount of deodorizer.
If you’re getting stench from your freshwater or hot water tank, see this page: Caring for your fresh water system
Happy Camper is the most often recommended odor reducer. It works a little differently.
This highly concentrated water-activated mineral blend eliminates odor without covering it up with perfume like many of the chemical deodorant treatments. Happy Camper works most like an enzyme or bioactive treatment but is not affected by residuals (previous tank treatment chemicals) and unlike enzyme treatments you do not need to regularly add more treatment.
The performance of Happy Camper is not affected by extreme hot or cold temperatures and is not harmful to the environment; in fact, it’s biodegradable. Happy Camper is a highly concentrated mono-hydrate blend of minerals and micro nutrients.
Happy Camper has been banned in California because of some of the ingredients.
Stench while showering
Some folks complain that they smell sewer gas from the gray tank while showering. It’s very likely this smell is is from the hot water heater. See this page to determine if that is your issue and what can be done: Caring for your fresh water system
Tip 4: Check your RV toilet for cracks, seal leaks, and recalls
The Dometic 300 RV Toilet issued a recall to correct a flaw in the seal design. If you have this type of RV toilet, contact the manufacturer for replacement instructions. Dometic would rather call the problem a “warranty issue” but, whatever…call this number 800-544-4881. You should be sent a Dometic 310 as a replacement.
Plastic toilets can crack if not treated gently. The ball valve seal can also have issues closing tightly. If the toilet bowl holds water the, seal is good. If the water drains out without flushing, the seal is bad and black tank stench can come thru. A replacement seal kit is about $15.00*. You could also try a seal lubricant and conditioner.
The gray RV holding tank can stink too
If you have stink in your RV that’s not from the black tank it may be coming from the gray tank.
Check under the sink to see if there is a vent like this. These go bad sometimes and allow air out instead of just in. You might find these under the kitchen or bathroom sink or by the laundry connections. Easy to replace.
Feel free to add the same deodorizer to your gray tank that you use in your black tank. Pour it down a sink drain with some water.
Larger RV’s can have two gray tanks. Look under the RV to see if you see plumbing running from a second tank. Add some deodorizer down a drain in the area of the second tank.
How to Dump Your RV/Travel Trailer Water Tanks
Everyone develops their own meticulous method of dumping their RV’s tanks, but the basics are the same. This is how I do it:
- Don your rubber gloves.
- Connect your tank drain to the dump stations inlet with your “stinky-slinky.”
- Dump your black water tank first. Fill the toilet with soapy water and flush to rinse the tank.
- Once drained, close the black tank drain valve and open the grey water tank valve.
- Drain the grey water tank. Fill the sink with soapy water and drain it to rinse out the grey tank.
- Once the draining is complete and valves are closed, add the Digest-It fluid and some water.
Seeing what’s happening
Click on image to order from Amazon. There are many types to choose from, but this is my favorite.
My dad always had me run a garden hose into the bathroom of the travel trailer and flush the black tank via the toilet until it was completely clean. Never use your fresh water hose to do this.
The elbow shown here securely connects into dump station connection. It fits four sizes of dump station inlets. Elbow is clear so you can see when your sewer hose has finished draining and is clear of debris. The fitting rotates 360 degrees and detaches from 4 in 1 adapter to fit into 4″ square RV bumper.
If your black water tank is directly below the toilet, you can get a pretty good view of the inside but there are some areas you can’t see or reach with a hose.
There is a version of this Elbow joint with a hose attachment so you can blast water up into your tank and make sure the drain is well cleaned out.
Finding RV Dump Stations
See RVer’s Guide to Dump Stations shown here. It’s a list of over 2000 dump stations across the US.
Also see this app “Map of RV Dump Stations“. This app shares the location of dump stations you have found and added. It’s growing and becoming more useful. Here’s another list called “Sanidumps: RV Dump Station Directory.”
How to Clean a Dirty Black Water RV Holding Tank
It’s very important to thoroughly clean your black tank after dumping. If you don’t, it will smell bad and your tank level sensors can become hopelessly clogged.
Here are some easy ways you can accomplish the cleaning without too much fuss:
RV black water tank cleaning method #1
Take this tip with “a grain of salt.” If your RV or travel trailer is able to be moved without too much fuss, dump a 10 lb. bag of ice cubes down the toilet after dumping. Add some cold water and dish soap, then take your rig for a drive. The ice cubes supposedly will dislodge hardened excrement, then melt away. This YouTube® video pretty much disproves this method, but a lot of people say it works.
Black water tank cleaning method #2
The Camco RV Flexible Swivel Stik with shutoff valve creates a powerful cleaning action that dislodges and flushes stubborn waste deposits and combats odors.
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- Powerful rotary cleaning action dislodges and flushes the stubborn waste deposits and odor-causing particles left after holding tank is emptied.
- Solid section including handle measures 24″ long; the flexible section measures 34″ long with a 2″ diameter nozzle.
- Flexible section is perfect for use with holding tanks that are offset from the toilet.
- Easy grip handle with a standard 3/4″ female garden hose connection.
Watch this video to see how easy it is to use:
Black water tank cleaning method #3
Over time, waste can accumulate inside even a well-maintained black tank for any number of reasons: parking an RV out of level, sagging tanks, the shape and/or design of your black tank, or even because of the way the discharge pipe is positioned. Deep cleaning your black tank with Clean-It is like power-washing your tank to ensure nothing gets left behind to cause problems.
Here is what you’re going to do:
- Close your black tank valve
- Fill your black tank with water
- Pour an entire bottle of Clean-It into your black tank (don’t forget to shake it well!)
- Let Clean-It sit in your tank for 48 – 72 hours (or more!)
- Dump and rinse your tank, ideally for 20-30 minutes
The magic is in the time that you allow Clean-It to work inside your tank. Clean-It is powered by extra-strength bacteria and fast-acting enzymes that chew through the accumulated waste that is causing your tank to fill up prematurely.
There is no amount of time that is too long to let Clean-It work! There is nothing in Clean-It that will cause any damage to your tanks, valves, seals, or sensor probes, so you can rest easy leaving it in your tanks for extended periods of time! Just be sure you don’t leave your tank full of water if there is a chance of freezing.
Unclogging Your Black Tank
Most clogs are caused by not using enough water. Digesters like Unique, Digest-It can’t get to the solids unless they are under water.
Unique Clear-It RV black tank unclogger is the most concentrated and most effective microbial tank cleaner available today. Put billions of bacteria to work for you. Enzymes will immediately begin multiplying. These enzymes break down more complex molecules into something easily digested by the activated cleaners, completely eliminating sewer odor, sludge, blockages, human waste and all brands of household toilet paper.
- UNCLOGS ALL TYPES OF CLOGS including pyramid plugs, compacted waste inside black tanks, and blocked plumbing lines.
- BREAKS DOWN SOLID WASTE, including toilet paper, poop, and residual sludge – no matter how old it is.
- Dissolves toilet paper from sensors so they indicate tank levels properly.
Back flushing with the gray tank
Here’s a short YouTube® video demonstrating a simple method to clear a clogged black tank using the gray water in your drain hose to back flush it.
Before replacing faulty black water holding tank sensors try this
Misreading black tank sensors are an all-too-common problem and though many products claim to help restore sensors, all of them fall short of success, except Unique Restore-It. Sensor restoration is a tough problem and Restore-It is the toughest, most effective treatment on the market. If you want a real solution for your misreading black tank sensors, Restore-It is it!
Reusing Your Gray Water
If you are a full-time RV’r on your own property, you can install a diverter in your drain line to send gray water to your garden and plants. It does need to be filtered properly. Here’s more on reusing your grey water.
If You Smell your RV Holding Tanks While Driving Your RV
Opening the front windows of the driving area of your RV will suck air from the back of the RV to the front. If there is no inlet for air in the back of the RV, the air will be sucked into the sewer vent on the roof and come in through the sink drains and toilet.
Here are some things you can do to combat this sewer back-drafting
This sink strainer was the key to blocking off the black tank stench while driving. Screw in tight.
- Pour some water down each drain, sinks, shower, and laundry. This will fill the P-trap that is supposed to normally block sewer gas. The back-draft can be strong enough to bubble past, however.
- Ensure that all of the sink drain caps are pushed closed.
- Replace the sewer roof vent cover with a Camco Cyclone Rotating Sewer Vent Cover.
- Put about an inch of water in the toilet to ensure there’s a good seal. If the water drains away, the seal is dirty, defective, and leaking. Add a layer of Vaseline or plumbers grease to create a better seal.
Here’s a manufactures video about installing the Camco Cyclone Rotating Sewer Vent Cover
Replacing A Broken Waste Valve for Your RV Holding Tanks
Sooner or later, the black and/or gray tank waste valve is going to break or jam. Don’t fret. It’s easily fixed. Don your rubber gloves first. Simply remove the four bolts, slip out the old valve, and slip in the new one. Replace the bolts.
It’s simple, if your waste tanks are empty. If your tanks are full, you’ll still use the same procedure but you’ll need to get creative in catching the poop water (eeew) that will escape through the valve area during the exchange.
Sometimes you can loosen the bolts and spray in some lubricant from the top so it drains down into the valve and frees it up.
Occasionally the metal handle unscrews from the shaft. If you can, screw it back on. If the threads on the shaft are stripped, grab the shaft with a pair of vise-grips and try to open the valve that way. Replace the valve once the tank has drained.
Mess-Free Waste Valve
For those of us who have a hard time bending over and reaching under the RV to open the waste valve, here is a waste valve with a six foot cable so you can open it standing upright.
More pages on this website you’ll want to visit
For ways to reuse your gray water visit this page.
To learn how to empty your tanks remotely visit this page.
Here’s how to add extra stinky-slinky storage.
Some good info about adding a DIY septic system to your permanent site.
Here’s more about septic systems if you’ll be living full time in your RV.
Thank u