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The Absolute Truth On How Fix A Clogged RV Toilet AND Eliminate The Possibility Of Future Clogs When RVing

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By Curtis

Is your RV toilet clogged?

The typical RV toilet

I’ve discovered that the majority of online articles on the subject of unclogging an RV toilet were clearly written by someone who has never owned an RV — much less used an RV toilet!

Hence I say, with authority, if you want the straight poop on RV toilet use and maintenance, you have come to the right place!

I’m going to show you what to do if your RV toilet keeps clogging…

RV Toilet vs. Household Toilet

The only thing a regular household toilet and an RV toilet have in common is that they are both sat on and used to properly dispose of human waste. That’s it!

  • They do not operate the same way.
  • They have few components in common.
  • And most importantly, the plumbing involved and what happens when you flush them is totally different!

A household toilet has a P-Trap hidden within its ceramic body, like this:

RV plumbing diagram

The P-Trap will always have water in it — which you can see in the bottom of the bowl — and requires the gallons of water stored in the toilet tank to flush the waste through the trap and down the plumbing. When a household toilet becomes clogged, the P-trap is usually where the problem lies.

An RV toilet has no P-Trap. It’s usually a short, straight shot through the toilet and right into the black water tank — as seen in this RV plumbing diagram by RV Insight:

The little bit of water in the RV toilet bowl is enough to keep the toilet seal lubricated — so odors don’t come into the RV.

Things You Should NOT Do If Your RV Toilet Is Clogged

All the standard methods of removing a clog are useless when it comes to RV toilets:

  • Forget the plunger.
  • Drano is of no use.
  • And never use anything metallic (like a drain snake) to clear an RV toilet clog.

RV toilets are made of relatively light-duty plastic. Metal (and even hard plastic) can easily damage the flush valve at the bottom of the bowl — causing the water that should be sealing the bottom of the bowl to drain through.

Always Do This To Prevent RV Toilet Clogs

An RV toilet is very different from a household toilet.

In reality, there is no such thing as a clogged RV toilet — because everything falls straight down into the black water tank. At worst, I’ve seen the exit pipe in an RV toilet go off at a 45-degree angle, but that’s still a very short fall right into the black tank.

In RVs, a clogged toilet problem almost always lies within the black tank itself and is usually caused from lack of understanding about how RV toilets should be used.

There is one golden rule with RV toilets:

Always leave the black tank drain valve CLOSED — until you are ready to dump the tank!

(If you have any doubt, the black tank valve is the one on the large pipe. The smaller one is gray water.)

When you’re connected to full hookups in an RV campground… yes, you must still always leave the black tank valve closed until the tank is nearing full. Then dump the tank and re-close the valve.

RV water tank valves

You can leave the gray water valve open to drain all the time, but the black tank valve must remain closed.

The reason behind keeping it closed is to maintain water within the tank — so that solids will break up and easily flush out of the black tank when it’s time to drain it. If the liquid is allowed to run off, the solids will create a mass in the tank that will clog the tank and plug up the black tank drain plumbing.

Skimping on the amount of water you allow to go through the toilet will greatly increase your probability of clogging the black water tank — because waste material cannot breakdown without water.

What About RV Toilet Paper & Toilet Chemicals?

RV dealers really love selling you on special toilet chemicals and special RV toilet paper — both of which have little or no value.

I use the cheapest toilet paper from Walmart in my RV and never once has my RV toilet clogged.

In 50 years of RV ownership (7 of which have been full time), I have never used toilet chemicals or RV toilet paper.

Also, I have never had an RV odor problem. If you do, it’s likely to be a roof vent issue.

The cheapest toilet paper at Walmart breaks down almost instantly. Just don’t go nuts on the quantity you use. The fact is nature and water will breakdown the solids as well as any chemicals you could add.

What You Should Do If Your Toilet Is Clogged

If all this information comes to you after the fact and your black water tank is currently clogged, here’s how to fix a clogged RV toilet:

  1. Open the black tank valve, push a garden hose up into the tank from that end, and run lots of water into the tank. (This will be messy!)
  2. Fill the black tank with water through the toilet. Add RID-X or a similar product with septic tank enzymes that will eat away at the clog. Don’t expect a quick fix though. These products are designed to be added monthly to keep a septic system clean, rather than just once to fix a clogged toilet.
  3. If you’re going to try a toilet snake or auger, do it through the black tank valve — not the toilet! It’s not likely to do much, but it’s also not likely to damage things that way.
  4. A flexible swivel stick (black tank sprayer with a shut-off valve) may make it easier to clean out your black water tank.

Hopefully this clears up what appears to be confusion about RV toilets — specifically, how to fix a clogged RV toilet.

Remember, lots of water going down the toilet is a good thing in RVs.

In this video, I’m showing how RV toilets work and sharing a few tips for fixing a clog in your RV:

Another Preventive Option Is To Use The Black Tank Flush

Many newer RVs come standard with a Black Tank Flush connection. it’s usually located close to the City Fresh Water connection.

Two tips before using your Black Tank Flush for the first time:

Your RV's black tank flush connection is located close to the City Fresh Water connection.
  1. Be careful not to mix up the 2 connections — because if you hook the city water hose to the flush connection, you will have water overflowing in your toilet or coming out the roof vent pipe for the toilet!
  2. Be sure to not use your clean, white, fresh water hose — instead, use a dedicated garden hose that won’t be used for potable water in the future to flush out your black tank.

How And When To Use The Black Tank Flush

With your dedicated black tank hose connected, open the black tank drain valve and use water pressure through the Black Tank Flush connection to spray the interior of your black tank. This will dislodge any solid matter that’s left inside the black tank.

TIP: Regularly spraying water through the Black Tank Flush connection will possibly help keep the level sensors clean too.

How often should you use of the Black Tank Flush option?

Whenever it’s convenient for you to do so:

  • At the end of an outing
  • A few times during the season

In my case, as a full-time boondocker, I seldom get the opportunity to flush my black water tank.

What About Clogs In RV Toilets That Have A Waste Grinder?

Sometimes, due to the layout of the RV, the black water tank is not located directly below the toilet.

RV macerating toilet

In these cases, having a toilet with a built-in macerator pump (or grinder) can help prevent clogging within the piping between the toilet and the black tank.

For example, the Dometic Master Flush Macerator Toilet is one RV toilet that comes with a built-in macerator pump:

RV macerating toilets claim to be able to flush with as little as 1 quart of water. But, trust me on this — 1 quart is the minimum! More water is better, in order to prevent your toilet from clogging.

Here’s why… As with a household toilet, it takes water to literally push the waste through the piping. If you send more water through the RV macerating toilet each time, then once the pump grinds it up there will be enough liquid for the output to make it through the plumbing and into the tank. Trying to conserve water with a macerating toilet will increase your likelihood of having RV toilet clogs.

Also, less is better when it comes to toilet paper. And never try to send anything other than toilet paper through an RV macerating toilet system!

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See how to fix a clogged RV toilet yourself (most online tips are WRONG!)