The Complete Guide to Fixing an RV Black Tank Clog

There isn’t much that can create panic for RV owners, like a malfunctioning RV black tank. The black water holding tank system is pretty straightforward. You have a holding tank that captures human waste from the toilet and a valve that opens up the drain, allowing you to empty (dump) your tank. However, what happens when this doesn’t work as it should, and you can’t drain your RV’s black tank?

This issue isn’t fun to write about, nor is it entertaining to read. However, you found the right place if you have a problem with a clogged RV toilet or RV black tank clog, and it won’t drain.

One of the most common issues with a black tank that won’t drain and is causing a backup in your RV toilet is something RVers describe as “poop mountain,” poop pyramid,” or “pyramid plugs.” It’s not fun to think about, but you should be aware of it using your RV toilet. This phenonium is caused by solids piling up in the black tank rather than mixing with the slurry water to dissolve. The most common cause of this situation is the lack of water. This problem can occur right below your toilet connection or at the valve, preventing the blackwater tank from draining.

Water is critical for your Black Tank.

You create a mini wastewater septic tank when using your RV toilet. By adding chemicals or RV tank enzymes, you allow toilet paper, solid waste, and liquid waste to mix and break down into a liquid slurry, which you can then easily empty when it’s full.

While you need all three of these components for a healthy black tank, you don’t want to forget to add fresh water. You need the water to disperse the solids, so they don’t pile up on the bottom of the tank and create a mountain. When solids interact with the black tank additive and water, they’ll begin to break down. While additives aren’t necessary, they will break everything down faster, which is often necessary when camping. The additives will also help with odor. However, the solids won’t break down if you don’t have enough water (or liquid).

When using your blank tank, always start with a few gallons of water in the tank. Then, after you dump, simply add at least a gallon of water by flushing the toilet and dropping in the treatment capsule or powder.

A bit about black tank treatments

There are dozens of options for tank treatment, but most will advertise odor control and different fragrances. So again, I suggest choosing function over flavor. I have tried dozens of brands, but the Happy Camper brand is my absolute favorite. This powder dissolves the solids super-fast and provides excellent odor control.

If the odor becomes an issue on hot summer days, I keep a bottle of fragrant fabric softener and put a little in the tank. However, I rarely have to do this with Happy Camper. Happy Camper also works great for the grey water tank, which I use periodically to keep it nice and clean. This additional step is especially useful for keeping your tank sensors functional.

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05/20/2023 10:43 am GMT

How to fix a clogged toilet?

Sure, prevention is the best way never to have to worry about a clogged black water tank, but what do you do if your RV toilet clogs? Luckily, This is a common problem, and solving it isn’t too difficult. Below are a few things you can try, and one is bound to work.

Water, chemicals, and time

This method is probably the least effective, but if you have time to let your black tank sit, this is one of the easiest ways to tackle a clog that’s “not too bad.” First thing, select a powerful black tank chemical treatment that advertises fast breakdown of solids. I like to use two (an extra) scoops of Happy Camper. Then, fill your black tank with water to cover the solids and add the extra treatment medium. This technique usually works best in warmer temperatures. You can even let it sit for a week or two if you’re between camping trips. Eventually, the solids will break down.

This technique is not necessarily my recommended approach because it’s not an instant solution. Also, if the clog is bad and you can’t get water into your tank, it may not work. However, it will eventually work if you do this and wait long enough. The worse the clog, the longer it will take.

Hot Water Method

Another cheap technique is to clear out a clogged black tank using hot water. Some people suggest using boiling water, but I suggest letting it cool a bit, so you don’t cause any damage to the rubber seals or plastic in your black tank. Heat some water on the stove, and once it starts boiling, turn it off and let it cool a bit. Pour at least a gallon of the hot water into the toilet bowl and let it sit for an hour or two, then try to drain your tank. You can repeat this process if it doesn’t work the first time.

Ice and drive method

Another method suggested by fellow campers is the ice cube method. The theory behind this technique is that the ice cubes act as an agitator when you drive around. The tank liquids and ice will slosh around and hopefully dislodge the solids pile, causing your clog when moving. It’s best to try to fit in two full bags of ice if you try this. Also, add it before you drive so it doesn’t melt and become ineffective.

The downside to this method is that you must do it when you leave, or you’ll have to pack up your RV. Also, once you dislodge the clog, you should try waiting a couple of days for the solids to dissolve before you dump it. This solution is best to try at the end of a campground stay or travel between sites. This solution is not terribly helpful if you’re in the middle of a camping trip and need to dump your tank.

The Broom Stick Method

This technique is probably my least favorite method since it can be messy, and you may never want to use the broom again. You don’t need a broomstick, but you want something rigid that won’t break. With the toilet valve open, stick a long rigid pole down into the tank and push things around.

This technique will only work if you have a straight opening into your RV toilet holding tank. If the clog is within reach of the stick, you should be able to break it up and solve your problem.

RV toilet wand

This following technique requires an extra tool, but it will work almost every time. If you don’t currently have a black tank wand, it’s a good idea to pick one up so you have one when you need it. A wand is a simple black tank cleaner tool consisting of a pipe or hose with a nozzle at the end that provides a power-blasting spray to break up whatever’s causing the clog. It’s kind of like a drain snake for the RV toilet. RV toilet wands are often a lifesaver for stubborn clogs.

There are two types available: 1) A straight, rigid pipe and 2) a flexible hose. If your toilet has a straight opening into the black tank, that rigid one is for you. However, if your toilet has an angled pipe into the black tank, you’ll need to flexible hose model.

A wand is an inexpensive piece of equipment for your RV toolbox. A few manufacturers make a wand, but my favorite is the Camco brand. Camco offers both a rigid and flexible model. They also sell an accessory, the flush valve prop, which holds your toilet valve open and prevents spray water from coming back up the toilet.

05/20/2023 11:33 am GMT

Black Tank Flush

If your RV has a built-in black tank flush, definitely give this a try. It will work similarly to the wand using high water pressure to blast away clogs with a built-in spray nozzle, but you don’t need a separate piece of equipment. The flush is often used for cleaning the tank, but if waste water can drain from your black water valve, you can connect a garden hose to the flush port on the RV and let it run for a while.

I highly suggest you invest in a separate hose and not use your fresh water hose for this purpose. This step is best done when connected to a sewer or dump station. You can use a lot of water, so a portable waste tank is time-consuming. You may want to try the wand if it doesn’t work at dislodging the clog.

Gray water backflush

This easy technique may be the solution if you’re at the campsite and run into a clogging problem. This technique works best for clogs at the flush valve of your black tank. I’ll do my best to describe it, but it will make sense when you watch the following video example. The good news is that you don’t need any additional equipment, just the sewer hose connected to your RV black water tank.

This technique uses water from your gray tank to backflow into the black tank and removes the clog. It’s best to attempt this technique with two people. First, close the black tank gate valve when you notice that your black tank isn’t draining. Next, you will want to open up the greywater dump valve and fill the sewer hose with water from your grey tank. Next, as soon as the hose is full and before it drains into the sewer connection, lift the hose above the height of the gray water tank. Next, close the grey tank valve(s). Then, open the black tank valve with the hose still held up in the air. This step will allow the water in the hose to flow up the outlet of the black tank, hopefully dislodging the clog. Once the water backflows into the black tank, quickly drop the hose to the ground. The force should be enough to suck the clog right out of the tank. If it doesn’t work the first time, you can repeat it until it does.


While a clog in your RV black tank or toilet is annoying, it doesn’t need to put a damper on your camping trip. The main reason for this problem is typically not using enough water in your tank or failing to add a treatment chemical on a regular basis. The suggestions listed in this article should be enough to fix almost any RV black tank clog. However, if all else fails, and as a last resort, you can always call a septic cleaning company. Hopefully, with the tips provided above, you can handle it on your own.

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