How to Unclog an RV Toilet, Sink, or Shower: Pro Tips for Unclogging Any Tank

RV plumbing is more sensitive than the plumbing in a typical home. Black and gray tanks can easily become clogged with waste (in the case of the black tank) and food, hair, or grease (in the case of the gray tank). Clogs will render your RV toilet unusable and can result in smelly gray water backing up in your sinks and shower. Clogs can happen for variety of reasons—maybe you forgot to close your black tank valve, or maybe it's been a while since the last thorough tank cleaning. Whatever the reason, most clogs can be cleared with the right method and a little patience. Learn more below, or see all RV sewer products now.
Read on to discover:
  • How to Unclog an RV Toilet or Black Water Tank
  • How to Unclog an RV Gray Water Tank, Shower, or Sink
  • How to Prevent Future RV Tank Clogs
RV Toilet and Drain Cleaner

How to Unclog an RV Toilet or Black Water Tank

The ProblemYou opened the black tank valve but can't see/hear anything draining. Or, a clog has formed in the pipe between your toilet and tank.The CauseFirst, make sure the real problem isn't actually a valve issue, rather than a clog. Sometimes the handle of the drain valve will move without opening the inside gate.If your valve is open and functioning correctly but your tank still won't drain, you likely do have a clog. A common (and dreaded) phenomenon in RV black tanks, often referred to as a "poop pyramid," is a likely culprit. These are particularly common if you forget to close the black valve after dumping, thus allowing all the liquid to drain out and leaving only solid waste behind to accumulate in the tank. Waste matter then builds on top of this initial layer, growing until the tank is completely blocked.Another possibility is a toilet paper clog. The chances of acquiring a toilet paper clog can be drastically reduced by using RV-friendly toilet paper and by keeping plenty of water in the tank at all times.The SolutionA clogged black tank is one of the worst issues an RVer can face. Fortunately, there are a variety of methods that can clear a clog and get your tank functioning again.
Unclogging an RV Toilet
Situation Level:
Basic Blockage
Situation 1 Emoji - Basic Blockage
Hot WaterMany basic clogs can be eliminated with this simple, effective method, so this is a good place to start. (Don't worry, hot water won't melt your toilet or damage your plumbing.)
  • Boil 1-2 pots of water
  • Turn off water connection
  • Pour hot water into toilet
  • Let water sit overnight
  • If necessary, add another pot the next day
Situation Level:
Pick Your Potion
Level 2 Emoji - Pick Your Potion
Chemicals and DIY SolutionsIf hot water alone doesn't do the trick, you can try hot water with a drain opener or other additive, such as dishwashing detergent. Another popular solution is Calgon water softener with Dawn dish soap. Just avoid caustic chemicals such as Drano or bleach, which can damage your tank and seals.
  • If using store-bought chemicals, follow any instructions on the bottle
  • If using Dawn, pour 1/2-cup to 1 cup into toilet (you may need to experiment to find the right amount). You can also add Calgon water softener for best results. Follow with hot water.
  • Take a drive to let the solution slosh around in the tank; let sit overnight if possible (or as long as bottle instructions indicate for store-bought chemicals)
  • Empty the tank; flush thoroughly with water
Situation Level:
Snake It Til You Make It
Emoji Level 3 - Snake it Til You Make It
Drain Snakes and Toilet AugersStubborn clogs often require a more hands-on approach. Drain snakes and augers are the next line of defense against clogs that won't quit. Some RV toilets drop the waste straight down into the black tank below; if this opening gets clogged, it's usually easy enough to shove the blockage through into the tank. Other RVs, however, use an angled pipe to transport the waste into a tank that's offset from the toilet. This type of setup is more prone to clogging and more difficult to clear. Make sure to use a hand-operated auger if you go this route—motorized augers can puncture your plumbing. Also be careful not to scratch your toilet when inserting the tool.
  • Insert the snake or auger into the toilet
  • Maneuver the snake or auger as necessary through any bends in the plumbing
  • Twist the handle clockwise until you catch the clog with the "hook" end—don't get discouraged, this can take a while!
  • Remove the snake/auger and flush
Situation Level:
Obstinate Obstruction
Level 4 Emoji - Obstinate Obstruction
Flush Valves and Tank RinsersFor best results, try a flush valve in combination with the hot water or drain chemical methods mentioned above. Avoid using tools that are not designed for black tanks, such as power washers, which can damage your tank.
  • For best results, first loosen the clog with hot water and/or chemicals
  • Clear the tank with a flush valve like the flush king or a wand-style rinser designed for black tanks
  • Flush the tank until the water runs clear
Situation Level:
Colossal Clog
Level 5 Emoji - Colossal Clog
Go to the ProsIf none of the above methods work, you have two options: either throw out your RV and start anew, or call in the professionals. Since the first option isn't much of an option, you'll probably want to go for the second. Taking your RV to a professional service for unclogging/cleaning is a last resort, but for the most extreme cases, it may be the only option. The good news is that you can likely prevent future clogs by practicing good RV tank habits (read on below).
The Ice MethodWe would be remiss if we didn't mention that method highly touted by RVers—the ice method. The instructions are simple: dump ice in your tank, add water (enough so that the ice moves, but not so much that it floats), and take a drive to create friction between the ice and the clog. For a lucky few, this may do the trick. However, as often as the ice method is discussed in RV circles, the consensus is that this method works better in theory than in practice. Think about it—when was the last time you scrubbed anything in your house with ice, whether a clog or just a stubborn glob of food in a pan? By contrast, how often do you reach for hot water and a cleaning solution?If you're desperate, it certainly doesn't hurt to try. However, we don't rank dumping ice down your toilet as high on the list as the other common unclogging methods mentioned above.
How to Unclog an RV Gray Water Tank, Shower, or Sink
The ProblemThe gray tank valve is open, but little to no water drains out. Or, water is backing up in the sink or shower.The CauseIf your tank won't drain:First, make sure your drain valve is functioning correctly. Sometimes the handle of the valve will move, but the inside gate won't open and the water won't drain. If your valve is open and functioning correctly, you likely do have a clog. Gray tank clogs are less common than black tank clogs, but hair, food, and grease buildup can still gum up the tank and prevent it from draining.If water is backing up in the sink/shower:It's possible the gray tank is simply full. When the gray tank is full, water can flow back up and out through the lowest drain, which is why many RVers experience water backup in their showers. Some RVs have two separate holding tanks for the kitchen and bathroom waste water (the kitchen tank is often called a galley tank). If this is the case for your RV, make sure both tanks are empty. If a full tank is not the problem, you likely have a clog caused by hair, grease, or food buildup in your tank or drain.The Solution:Don't let a stubborn clog ruin your RV adventure. There are a variety of methods that can unclog an RV tank or drain, so you can get back to enjoying your camping experience.
Sink Filled with Water
Situation Level:
Basic Blockage
Level 1 Emoji - Basic Blockage
Hot WaterIf your tank isn't draining, the simplest clog-clearing method is to flush your pipes with hot water and clear out any gunk that has built up inside.
  • Boil 2-4 pots of water
  • Remove any strainers, caps, or drain grates if possible
  • Pour hot water into sink/shower
  • Let water sit overnight
  • If necessary, add another pot the next day
Situation Level:
Pick Your Potion
Level 2 Emoji - Pick Your Potion
Chemicals and DIY SolutionsIf hot water alone doesn't do the trick, you can also try drain chemicals specifically designed for clearing RV drains, or you could use what you have at home. Popular DIY options include Dawn dishwashing liquid and Dawn with Calgon water softener. Just avoid caustic chemicals such as Drano or bleach, which can damage your tank and seals.
  • If using store-bought chemicals, follow any instructions on the bottle
  • If using Dawn, pour 1-3 cups down each sink/shower drain (you may need to experiment with the right amount, depending on the severity of your clog). You can also add Calgon water softener for best results. Another popular solution is baking soda with white vinegar. Follow with hot water.
  • Take a drive to let the solution slosh around in the tank
  • Empty the tank; flush thoroughly with water
Situation Level:
Snake It Till You Make It
Emoji Level 4 - Snake It Till You Make It
Sink Plungers and Drain Snakes/Hand-Operated AugersFor a more hands-on approach, sink plungers and drain snakes/augers can also be used to clear a backed-up drain. Make sure to use a manual/hand-operated auger if you go this route (rather than a mechanical auger, which can damage your RV plumbing). A pair of long tweezers or pliers can also be used to remove hair from drains. You can also try removing your sink's P trap and manually clearing out any gunk causing the clog.
  • Carefully insert the snake or auger into the drain
  • Twist the handle (if there is one) clockwise or maneuver the tool to hook the clog—don't get discouraged, this can take a while!
  • Remove the clog and flush the drain with water
Situation Level:
Obstinate Obstruction
Level 4 Emoji - Obstinate Obstruction
Flush ValveFor best results, try a flush valve in combination with the hot water or drain chemical methods mentioned above.
  • First loosen the clog with hot water and/or chemicals
  • Clear the tank with a flush valve like the flush king
Situation Level:
Colossal Clog
Emoji Level 5 - Colossal Clog
Go to the ProsIf none of the above methods work, it may be time to bring in the big guns. Taking your RV to a professional service for unclogging/cleaning is a last resort, but for the most extreme cases, it may be the only option. The good news is that you can likely prevent future clogs by practicing good RV tank habits (read on below).
How to Prevent Future RV Tank ClogsClogs are a major inconvenience, to be sure, but the good news is that they are not inevitable. With proper tank maintenance and a few simple precautions, you can spare yourself the headache of having to clear out a clogged black or gray tank ever again.
Black Tank Clog Prevention Tips Infographic
Black Tank Clog Prevention Tips:
  • Use RV-safe toilet paper: Regular toilet paper designed for household plumbing can cause clogs in RV black water systems. RV-safe toilet tissue breaks down quickly, helping to prevent clogs.
  • Clean and treat your tank regularly: For tips on properly maintaining your black water tank, read more here.
  • Use plenty of water: When it comes to black tanks, the more water, the better. Make sure to use enough water whenever you use the toilet to prevent paper and solids from sticking. Also make sure to add a layer of water to the bottom of the tank each time you dump.
  • Never leave your black tank valve open: Although the gray tank valve can remain open at the campground, you should never leave your black tank valve open. The liquid inside the tank will drain out, leaving behind a mess of solid waste in the flat tank bottom. The waste will harden and cause a clog, or "poop pyramid."
  • Dump the black tank at 2/3 full: It may seem like a great idea to empty your black tank as often as possible at the campground, but it's actually better to wait until your tank is at least 2/3 full. This way, there will be plenty of water to suspend the solid matter and allow the tank to drain.
  • Never use your toilet as a trash can: It may seem obvious, but your toilet is made to flush human waste and RV-safe toilet paper. Nothing else. Spare your plumbing (and spare yourself a future headache) and toss any cleaning wipes, hygiene products, etc. in the trash can where they belong.
Gray Tank Clog Prevention Tips Infographic
  • No food, hair, or grease: Your RV plumbing system is more sensitive than a typical household system. Even a small, seemingly harmless amount of food (coffee grounds, peas, etc.) or hair can gum up the works. Always scrape your dishes clean before rinsing them in the sink.
  • Use a strainer: Sink strainers are an easy, economical way to prevent solids from making their way down your drains.
  • Clean your tank regularly: Yes, your gray tank needs maintenance too! For tips on cleaning and treating your gray tank, read more here.
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Related ProductsWritten by: Amber S.Updated on: 11/16/18


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