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Why Is My RV Toilet Leaking?

RV toilet Leaking? Don’t fret! Having a leaky RV toilet is common and every one we have had has eventually leaked. Usually, it’s a cheap and easy fix. It might not be what you wanted to do on your Saturday afternoon, but it won’t take you away from your adventures for very long. Let’s look at what causes an RV toilet to leak and steps to fix it.

What Causes an RV Toilet to Leak? 

RV toilets have 3 primary leak points, the ball seal, water valve or flange seal.

RV toilet leak points diagram schematic
This exploded view diagram of an RV toilet shows the most common leak points

Most of the time, an RV toilet leaks at the base because a seal has worn out. If you keep your RV in storage a lot, the seals can wear out from lack of use. If you use your RV often, the seals simply wear out over time.

A leak could also be from the water valve that controls the water flow to the toilet. These valves can leak water into the toilet or sometimes around the base. Sometimes it’s the connections to these valves as well that can be the culprit.

Lastly and the worst reason for a leaking toilet is a crack, which means you have to replace the whole thing. But that is less common. Typically, you’ll have a flange, ball seal, or valve that you need to replace.

RV toilet leaking at base
RV toilet seals wear out over time and must be replaced.

Pro Tip: Learn all the parts of an RV toilet in our article all about them.

How Do I Fix a Leaking RV Toilet Base? 

Sometimes it can be hard to tell where the toilet is actually leaking from. Even a leak at the valve might run down inside the toilet and end up coming out the base. It’s critical to find out where the leak is actually coming from, and the first step is usually to inspect the water valve.

If you identify that the leak is coming from the base of the RV toilet only, then you probably need to replace the lower flange seal. This seal goes between the toilet base and the floor.

You know that this is the leak’s location when the toilet only leaks after flushing. Thankfully, you can easily repair it, and it should only take an afternoon. 

Make sure to purchase a new flange seal that matches your toilet model. RV toilets don’t use standard plumbing parts, so you’ll need to get an RV-specific repair kit. You can find them online at Amazon, Camping World, or an RV dealer.

To replace the seal the toilet will need to be removed, more on that in a bit.

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How Do You Fix a Drip That Is Not At The Base?

What if you notice the toilet is leaking higher up, or running down the side? This most likely indicates a valve leak or sometimes a ball seal leak. Usually, the first thing to do if you notice a leak higher up and usually from the back of the toilet is try tightening the hose fittings connecting the toilet. These are sometimes plastic threaded connections or held on with a hose clamp.

If this does not fix the valve leak the valve might need to be replaced. This will require disassembly.

DIY Steps to Fix an RV Toilet Leak

You won’t need to take your RV to the dealership for a leaking toilet. You really don’t need to call an RV mobile tech either.

Anyone can replace the flange seal, water valve and sometimes a ball seal with a few instructions. So let’s take a look at how to fix a leaking RV toilet base yourself.

Were going to share the general steps we would take to repair a toilet, but if you know your toilets model you can also search Youtube for a repair video. Chances are someone else has already done this.

Step 1: Shut Off Water 

You must shut off the water first. This ensures that you don’t have an even bigger mess to clean up. You don’t want water pouring in while you try to replace parts. 

RV water hookup
If hooked up to water at a campground, be sure to disconnect from the water supply before fixing the leaky toilet.

Most RVs have a valve leading into the toilet you can simply turn off. If yours doesn’t, disconnect from your water source if you have hookups. Turn off the water pump if boondocking.

After the water is disconnected open all faucets and depress the toilet flush to relieve pressure and drain water. Because the toilet is lower than other water fixtures, it usually will leak water even if the water has been disconnected.

Step 2: Drain and Disconnect Toilet Lines

After the water is disconnected open all faucets and depress the toilet flush to relieve pressure and drain water. Because the toilet is lower than other water fixtures it usually will leak water even if the water has been disconnected.

If the toilet continues to fill your water pump may be on, make sure that’s off too.

Once drained find the water connections to the toilet and disconnect them. They are usually on the side or back of the toilet. Have a towel nearby when doing this as the lines may still leak a bit.

removing RV toilet
You may need to remove the toilet shroud to access the water lines to disconnect them.

Step 3: Remove the Toilet from the Floor

You’ll need a good socket set to remove the toilet from the floor as two or three bolts hold it in place. A u-joint and long driver extension bar will make removing the hard-to-reach toilet flange bolts much easier. Sometimes the bolts have caps covering them.

RV toilet bolts

Pro Tip: Every RVer needs a well-equipped tool kit. Check out what’s in ours: 36 Important Tools You Need In Your RV Tool Kit.

Once the bolts are loose the toilet should wobble a bit, remove them the rest of the way and lift the toilet straight up. Have some towels nearby when removing the toilet.

I recommend using a rag or aluminum foil to cover the drain hole after the toilet is removed. This keeps the smell down and prevents any tools from falling down the hole and into the black tank. You might also want to set the toilet bowl on a garbage bag to protect the bathroom floor.

RV toilet draing hole cover
our toilet drain hole covered with aluminum foil as it conforms to the weird shape and is disposable.

Step 4: Replace the Seals or Valve

With the toilet removed now you can get at the three parts that most commonly leak.

Flange Seal

Next, find the flange seal, usually located around the drain hole. Sometimes the flange seal can get sticky, making it hard to remove. Check to see if it got stuck to the bottom of the toilet, and use a putty knife to help pry it loose. 

old leaking toilet seal
An old nasty RV toilet flange seal

Here is a video showing an easy way to get the seal to re-seat by installing it on the toilet first.

How not to fix an RV toilet floor flange

Clean the area well because you don’t want to insert a new flange seal with a lot of gunk and grime around the hole. You may not have as tight of a connection if debris gets in the way.

Water Valve

If your water valve is leaking it’s usually easiest to take the toilet outside because it may leak more when doing this procedure. It is sometimes possible to replace the valve with the toilet in place if you have room, but it’s usually advisable to replace the flang seal when doing any other work as well as it is a common failure point.

Find the valve on the toilet, usually located on the back or the side. Usually, there will be two or three screws holding it in place. Remove the screws and pull on the valve. It is usually set into the toilet with a thick gasket or clips that can be a tight fit.

Once the valve is removed reinstall the new one in its place then reinstall the toilet with a new flange seal as above.

How To Fix A Leaking RV Toilet | Valve Replacement- Dometic 300 301 310 series how to fix rv toilet
This video explains a valve replacement, it will be a bit different for each toilet type.

Ball Seal

If your toilet doesn’t hold water, you might need to replace the ball seal. Thankfully, this is also a cheap and simple process that you can do yourself. Order a replacement ball seal that fits your model.

Ball seals differ the most in the replacement process but are usually the easiest. Many of them can actually be replaced with the toilet in place. Its best to do a search for your toilet type using the search term “{insert Toilet Type} Ball Seal Replacement”. There are many videos showing the different types and how to replace them.

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When you’re ready to fix the leak, turn off the water. Once back inside, hold down the pedal to open the drain. 

Like mentioned above there are lots of different types of toilet ball valves but here are a few videos of the most common types.

EASY RV Toilet Seal Replacement - Thetford RV Toilet
How to replace your RV Toilet Flush Seal Travel Trailer Toilet bowl Ball gasket Replacement #rv
Straight valve toilets are usually this type
Leaking rv toilet? Diy toilet seal replacement
Dometic’s are usually 2 piece toilets.

Step 5: Put the RV Toilet Back in Place and Test for Leaks

If you covered the drain hole, remove the rag and set the toilet back on the bolts. Make sure to center it over the new flange seal and drain hole.

Once you’ve connected it correctly, sit on the toilet. This will help secure the connection and set it in place. Then tighten the bolts. Beware that overtightening can break the toilet. You want the bolts to be secure but not torqued down.

repairing leaking RV toilet
You’ll need to remove the toilet to replace the flange seal.

After the toilet is back in place, clean the threads on the water supply nozzle. Sometimes the old sealant won’t hold well after you disconnect it, so you might want to add a new sealant or Teflon tape for added protection. 

Finally, turn the water back on and test the connections. Flush the RV toilet and check for any leaks around the base.

RV toilet
After you’ve secured the toilet in place, turn the water back on and flush to check for leaks.

Pro Tip: Need to replace your entire toilet? Use this Practical Guide to the 6 RV Toilet Types to determine your best option.

Is Fixing a Leaking RV Toilet on Your Own Worth It? 

It’s not a matter of fixing or not fixing a leaking RV toilet. You have to repair the leak if you don’t want to clean up water every day, repair water damage, or deal with awful smells.

Fortunately, you can save money by doing it yourself. The process isn’t difficult and doesn’t take very long. It might be gross, but it’s worth it. Did you do it? Let us know how it went in the comments below!

RV bathroom
Fixing a leaking RV toilet is a relatively simple and cheap repair.

We replaced our RV toilet with a composting toilet, so we never have to worry about leaks again. Find out the other benefits of this RV upgrade: What’s So Great About RV Composting Toilets?

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About Tom Morton

Tom, a Pacific Northwest native, is our technical genius. Born in Washington and raised in Alaska before settling in Michigan. He's the man who keeps our operation running, both figuratively and literally.

With a background in Electrical Engineering, Tom specializes in RV solar systems and lithium batteries. He made history as the first documented individual to use a Tesla battery module as an RV battery. Tom has personally assisted countless RVers with system installations and has educated thousands more through his videos and articles.

Cinematography is another of Tom's passions, showcased in his work on the Go North series. You can see his camera skills on display in The RVers TV show on Discovery Channel and PBS where he also stars as a co-host.

Tom's mechanical expertise extends beyond RVs to boats, planes, and all things mechanical. He's renowned for taking on maintenance and repair projects single-handedly and is often spotted underneath RVs, making him the technical backbone of our endeavors.

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Kitty G

Tuesday 19th of December 2023

One other leak culprit could be the vacuum breaker - we had intermittent big-time leaking from the upper back of our Dometic 310-series toilet - it would be fine for days, then fresh water would pour out the back, then OK again for a few more days. Their web site trouble shooting guide pointed to a failing vacuum breaker, which we replaced no problem.

Alan Buckner

Tuesday 19th of December 2023

For the toilet not holding water, I've found that using a liberal amount of Danco Waterproof Grease 80360 (found at Home Depot or maybe Lowes) around the seal works great but needs to be done about once a month. This works better & longer than other versions of Plumber's Grease, and beats replacing the ball seal often.

Mark

Friday 11th of August 2023

I have a Thetford AM 5 toilet that I have replaced the ball seal twice and it still will not hold water in the bowel. I am at wits end! I don't know what else to do. I tried using plumbers grease on the second seal replacement and it still is leaking. I guess I will have to change out the Toilet unless some one might have a better idea.

Mortons on the Move

Monday 18th of September 2023

Ugh, i know that problem. There is probably a warp in the plastic. Sometimes you can replace the entire ball mechanism.