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How To Unclog An RV Black Tank

You know when you are in for a treat when you are wondering about how to unclog something. The RV’s bathroom is an awesome thing to have when you want to use the facilities on the road without finding one. The black tank can also be pretty gross.

Unclogging your black tank can be relatively easy, thanks to some products and with some knowhow. We’ll teach you both how to know if your RV black tank is in fact clogged and what to do about it.

The first thing to do is to diagnose the problem. Then you can add some chemical fixers to the tank to break up the organic matter in the tank. The next step would be to drain again. Read on to know more.

How do know if you have a clog

The first sign of a clog is that your black tank drain gets backed up, which usually leads to a pretty unpleasant spell. The inability to get waste to stay down the drain is also a bad sign.

At this point, we suggest just trying to drain your black tank to get… something out of there for added relief. Whether it’s solid or liquid, it could help.

If you only end up draining out liquid, that’s at least a start. 

A couple of easy ways

If you know there is solid waste in your tank, but it doesn’t come up via draining, then you’ve got a problem. Your RV black tank might have a dreaded “poop pyramid” of solid waste that is stacked up but somewhat dried and unable to move. Note that some of our suggestions will probably result in shoving your hands into the toilet. Bring gloves!

Use Ice

Throw a couple of bags of ice into your toilet. Start the RV and drive around. The hope is that solid pieces of ice being tossed about might loosen up the clog without resorting to more measures. Ice is also generally quite cheap.

Try to drain your tank after driving around and see if anything else comes out.

Boiling Water

The opposite of ice! Boil water on your stove (or microwave, just got it hot) and pour it down the toilet, if it’s not already severely clogged. Boiling water can melt clogs ranging from hair to solid waste and make it possible to loosen up your system.

Be careful! Walking through your RV with boiling water can be a bit dangerous to tell others you are carrying a very hot pot.


We are not suggesting you unleash a reptile into your tank. A snake can be described a long, mechanical claw on a cable that can break up issues in your lines.

With a snake in your toilet, you might discover that the clog is in your plumbing lines instead of your tank.

One important suggestion here: Wear a mask and goggles in addition to having an assistant. The snake might come back with solid waste that you won’t want splashed everywhere. Bring a garbage bag in the event that a very solid piece of solid waste comes up.

GEO Method

The GEO method uses Calgon water softener and a transparent sewer hose adapter. The transparent adapter is to see the results as you flush.

First, pour the water softener into your toilet. Use as much as you need as it’s not harmful.

Connect your black tank to a sewer line. Once the softener is in the toilet, give it a flush. Try this every few minutes until the color of the water as seen through the transparent sewer hose adapter becomes more clear.

This won’t likely break up very badly clogged tanks, but it could make other methods easier and more fruitful.

Chemical ways to unclog your black tank

None of the above work? Well, the fight isn’t over yet. You can use chemicals, sparingly, to remove clogs in your black tank.

Don’t use chemicals like drano or other “clog removers.” They are generally not made for an RV and can be caustic to your pipes. The tank might also become more clogged in the process and you don’t want your black tank spitting chemicals back at you through your toilet.

Pour the chemical removed into the toilet. Let this sit for some time – maybe a few hours or overnight. Attempt to drain the tank after letting the waste and chemicals sit together for a while.

What if chemical remover doesn’t work?

Chemical remover is the strongest method and the last resort. At this point, you may need to either remove the black tank or find a way to get inside.

You might also need to ask for pro help at this point. A chemical remover should be capable of dissolving anything organic to the point of easy draining.

Preventing a clog in the future

Preventing future clogs is actually pretty easy. There are a couple easy things to do. Not flushing large, non waste objects is pretty obvious.

Keep your black water tank semi-full. You don’t need to completely drain it – in fact, you might want to fill it with some fresh water before leaving for a road trip. The largest contributing issue to major clogs within the tank is tissue or solid waste hardening and sticking to the tank. With consistent moisture and occasionally complete rinsing, you’ll have these issues less often.

If part of your issue was that someone (probably a child) flushed a non flushable object, consider closing the door to the bathroom when not in use. Or use a child proof knob. Most children who would throw a toy in the toilet to accidentally clog the line probably aren’t aware of the issues.


Unclogging your black tank can be an unpleasant experience. The above advice gives you many avenues to use to get your tank flowing again, using some resources you might have to go get.

We would like to reiterate the need for safety glasses and gloves while unclogging your tank. Getting splashed by waste is bad enough. Getting waste in your eyes and on your skin is pretty gross.

Start by determining if your tank is clogged or not and move from there. Hopefully the most simple method of clearing our your clog is above and helpful.

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