How To fix an RV toilet leaking on the floor

Sitting down to take care of business only to realize that you have a smelly liquid leaking from under your RV toilet is a rude awakening for anyone living in a camper. 

If there water on the floor around the base of your toilet, this means there’s a leak in your toilet.

A leaky camper toilet never feels like a simple problem to deal with. Whether water is leaking into the bowl or onto the floor, some plumbing work will be required to fix it. 

So, Why is My RV Toilet Leaking At the Base and how to fix it

You can fix a leaky RV toilet by first diagnosing the problem. RV toilets generally leak onto the floor for 1 of 4 reasons - a bad flange seal, a cracked water valve, bad internal seals, or a cracked bowl.

Second, once you know why your RV toilet is leaking, the solution can involve a simple DIY fix, a new RV toilet, or professional help.

This post will show you how to figure out why your RV toilet is leaking on the floor and the steps you’ll want to follow to fix the problem.

What Causes an RV Toilet to Leak on The Floor

What Causes an RV Toilet to Leak on The Floor?

First, let’s learn a bit of RV lingo. The rubber ring that seals your RV toilet to the floor is professionally known as the “Closet Flange Seal.”

It’s called a “closet” flange seal because your RV toilet is also known as a “closet”.

Don’t ask us why, we just know that it’s the case 🙂

The flange seal is usually but not always the cause of a leaky RV toilet. 

But before you go replacing your flange seal, you should know what else might be causing your RV toilet to leak around base.

Here are other several possible Causes of a Leaky RV Toilet that might be leaving your camper floor wet:

1. Cracked toilet bowl

While rare, your RV toilet bowl might have a crack in it that is allowing water to drip down.

In order to diagnose this, you would need to look all around the toilet bowl with a flashlight for any signs of leaks or cracks.

You could also wrap the bottom of your toilet bowl with an old towel and let it sit overnight. If you wake up to a wet spot on the towel, that should help you pinpoint the location of the crack.

How to Fix: You could try using sealant to fill the crack, but usually the best repair is to simply purchase a new RV toilet and replace your old one. 

That’s because you never know how many more cracks might be forming or if you can actually seal the crack well enough to stop a leak.

2. Bad Water Valve

RV toilet water valves are notorious for cracking and leaking if you allow your camper to get hit by a freeze.

Usually, if your RV toilet is leaking from the water valve, you’ll know it because water will be spraying out somewhere near where the water line hooks into the toilet.

How to Fix: Purchase a water valve kit like this one and be sure you get one that’s designed for your specific model RV toilet.

Then, you can follow the instructions in the water valve kit to replace the water valve on your toilet.

3. Bad Internal Seals

RV toilets have seals inside them that - among other things - seal the toilet bowl to all other pieces of the toilet. If these seals go bad, you’ll notice water leaking on the floor.

However, water will leak even when you’re not flushing. If water leaks onto your floor when you are not flushing, this could be the result of bad internal seals in your RV toilet.

How to Fix: You can either purchase a new toilet or hire an RV technician to disassemble your toilet and replace the seals.

This is not a project we’d recommend DIY’ing because it can get very messy if you don’t know what you’re doing. 

Replacing an RV Toilet Flange Seal to Stop a Floor Leak

Replacing an RV Toilet Flange Seal to Stop a Floor Leak

The “good” news is that it’s much more common for a flange seal to go bad than any of the above problems (e.g. bad water valve, bad seals, etc.) 

It’s relatively easy to confirm that a flange seal is causing your RV toilet to leak on the floor: 

  1. 1
    If your RV toilet leaks on the floor only when you flush, the chances are it’s a bad flange seal.
  2. 2
    Double check your toilet bowl for any visible cracks. If you don’t have any, you can probably rule this out as the source of your leak.
  3. 3
    Use a mirror to inspect all around your toilet as you flush to confirm that water is not escaping from your water line, or any area other than the bottom of your RV toilet (your flange seal lives on the bottom of your toilet).
  4. 4
    We’ll show you how to lift your RV toilet up in a moment, and when you do, you should double check the inside of the toilet stand for any signs of leaks.
  5. 5
    If you don’t see any leaks inside the toilet stand, this is a good sign that water is only leaking from the bottom - right where the flange seal meets the floor.

Assuming you confirm that your closet flange seal is causing the leak, please move on to the next steps to replace your RV toilet flange seal.

Tools You’ll Need to Fix an RV Toilet That’s Leaking

Fixing a leaky RV toilet doesn’t require any special tools. You should be able to complete the job with tools that most folks have laying around the house or RV.

Most modern RV toilets are also fairly standard, meaning you shouldn’t need any special skill or knowledge to fix a leaky toilet. Here are the tools you’ll need:

  • Replacement Closet Flange Seal for your specific RV toilet - RV toilets use a special kind of seal that is different from those used in household toilets. This Thetford seal, for example, is one that will fit a large variety of RV toilets. Note that RV toilet seals are made of rubber and have a special shape. CAUTION: Do not use a house toilet seal. These seals are usually made of wax and are not designed to handle the bumps of the road. If you use a wax seal on your RV toilet, you’ll be setting the stage for another leaky toilet very soon.
  • A Socket Set or Wrench - RV toilets are held down by 2-3 bolts that can be easily removed with a standard socket set or wrench. You might want an extension for your socket set if you have one, but this is not a requirement. An extension can help you get to hard to reach toilet bolts.
  • Old Towels - Water is going to get on the floor when you remove an RV toilet. Have lots of towels handy to dry it right up.
  • Utility Knife, Putty Knife, or an Old Screwdriver - You might need to pry off the old flange seal because it has gotten sticky over the years. Any one of these tools will help you in case there’s anything you need to pry off your RV toilet to make way for the new flange seal.
  • Teflon Tape - Always a good thing to have when working with plumbing. This handy tape will help you create a watertight seal on any threaded pipes. 
  • Cleaning Supplies - No matter how much water you drain out, you’re still going to get water on the floor. Also, when you pull your RV toilet up, you’ll expose areas that haven’t previously seen the light of day. Why not clean these areas while you’re working?
  • Rubber Gloves - RV toilets can be nasty. Wear gloves to protect yourself and others from the germs that might be down there.

How To Fix An RV Toilet Leaking Around the Base

Step 1: Shut Off the Water

Unless you want a bath as you fix your leaking RV toilet, you will need to shut off water going into your toilet.

Almost all RV toilets have a simple valve on the water pipe going into the toilet that will allow you to shut the water off. Turn this valve off to ensure that no water is going to the toilet.

Once you have water shut off to the toilet, you should flush it one last time to make sure that all the water is out of your RV toilet. 

If you don’t see your RV toilet shut off valve or simply want to be extra careful, you can shut off all water going into your RV and turn your RV water pump off to make sure no water gets into your toilet while you’re repairing your RV toilet leak.

Step 2: Disconnect Your RV Toilet from Water

Now that you’ve turned the water off and gathered your tools, you need to actually disconnect your RV toilet from the pipe that is providing it water. 

To do this, locate the water pipe running into your RV toilet. When you’re facing the toilet, this pipe will usually be on the bottom right side of the toilet. 

Once you’ve found the water pipe, you should notice a threaded end that is screwed onto your toilet.

See if you can unscrew it with your (gloved) hand first.If you can’t loosen the pipe with your hands, use a wrench to gently unscrew the water pipe from the toilet. 

Step 3: Pull the Toilet Up

Once you have the water pipe completely free from your toilet, locate the 2-3 bolts holding it down.

These bolts might be covered by white plastic caps which you can simply pull or pry up (while being careful not to damage them).

Once the bolts are exposed, you can simply use your wrench or ratchet to loosen the nuts holding the toilet down.

This is where you might want to use the extension for your ratchet set (if you have one) to reach the toilet bolts on the floor.

Be sure to put the toilet bolts in a safe place when you take them off so you don’t lose them!

Once you’re certain that the toilet bolts are removed and the water line is disconnected, simply lift your RV toilet straight up. It should slide off easily.

Be sure you have a towel or perhaps even a garbage bag ready to set your RV toilet on. 

Once your RV toilet is removed, you will need to locate the flange seal. Usually, this seal will be stuck to the bottom of your toilet.

Sometimes the closet flange seal will remain in the hole in the floor that goes into your black tank.

Either way, the flange seal is a small black rubber ring that you will need to remove to make way for the new seal. 

Step 4: Cover the Sewer Hole

Once you remove your RV toilet, you’ll see a hole in the floor with a black ring around it.

This is the drain going into your RVs black tank. You’ll want to stuff a garbage bag or old rag in this hole so you don’t lose any tools down the stink.

Step 5: Remove the Old Flange Seal and Clean Area

Once you locate the old flange seal, you should be able to easily remove it by pulling it off your toilet or prying it from the ring in the floor.

Sometimes the old seal might’ve gotten stuck to something in which case you’ll need to work a bit harder to get it out. 

Once the old flange seal is removed, clean the bottom of the toilet bowl and the sewer area in the floor so you have a good clean surface to install the new seal. Be sure there is no debris that would prevent a tight seal.

Step 6: Install Your New Toilet Flange Seal

The new flange seal will be a rubber ring. Many toilet seal makers also add an extra layer of rubber that tapers in.

This tapered layer serves to guide the water from your toilet into your black tank and provides an even better seal. 

If the flange seal you purchased comes with instructions, follow those for installing the new seal on your RV toilet. 

Generally speaking, however, it is best to put the flange seal directly on the bottom of your toilet rather than onto the hole in the floor.

If your seal has extra rubber that tapers in, you want this end going down toward the floor.

For example, a flange seal that has a tapered part will look sort of like a cone. You want to put the bottom of the cone down toward the floor so water flows through it more easily. 

Be sure that you don’t push the flange seal too far up the bottom of your toilet - you want to create a tight seal between your flange seal and the sewer drain in your floor. 

Step 7: Carefully Put Your RV Toilet Back Down

Now that your flange seal is on the toilet, you’re ready to place it back onto the drain.

Start by removing the bag or old rag you used to plug the drain hole, make sure all surfaces are clean and free from debris, and then gently set your toilet back down.

You will need to be careful to line your RV toilet back up with the screws in the ground that were originally holding it down.

Once you have put your RV toilet back down and feel that you have an even seal, you can use your wrench or ratchet to re-fasten the bolts you took off in step 4. 

Step 8: Reconnect Water and Test

Now that the toilet is bolted back down, you should reconnect the water. Start by putting new teflon tape on the threaded end to create a watertight seal.

You can then hand tighten the water pipe back to your toilet in the exact same place where you originally unscrewed it.

Once you hand tighten the pipe, you can use your wrench to tighten the pipe a few turns, but be careful not to overtighten.

Lastly, you can test your RV toilet with a few flushes. Make sure everything is flushing properly and also be sure to feel around the water line connection to ensure there are no leaks that started when you disconnected it.

And there you have it!  You’ve just fixed an RV toilet that’s leaking without having to take it to the shop.

Be sure to double check that the leak doesn’t continue, but so long as your floor stays dry during the week following the repair, you should be set for years of leak free bliss!

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