There’s not much worse than discovering your RV toilet is leaking (except perhaps discovering your black tank is leaking! ), but knowing what’s causing the leak will help you repair it as quickly as possible.
In today’s post, we’ll go over the numerous reasons why an RV toilet may be leaking, as well as what you can do to troubleshoot and remedy the problem.
Table of Contents
What Could Cause a Leaky RV Toilet?
When you discover a leak that looks to be coming from your toilet, the first thing you should do is explore the area to determine where the leak is coming from and when it is occurring.
Is water dripping from the upper section of the toilet when you flush it, for example? When the toilet bowl is full, does the leak occur? Do you have any water around the toilet’s base?
After you’ve pinpointed the source of the leak, you’ll be able to take immediate action to fix it.
Most RV toilets leak for one of the following reasons:
BAD FLANGE SEAL
This is the toilet-to-floor seal (like the wax seal under your home toilet). These seals can loosen or develop gaps over time, resulting in leakage.
Here’s an illustration of a Dometic flange seal and a conventional (supposedly universal) 3″ flange seal:
DOMETIC 385311267 Floor Flange Seal Kit
- Floor flange fits 110 and 210 Series Domestic RV toilets
- Seals to prevent leaks
Thetford 33239 Closet Flange Seal , Gray
- Closet flange for Thetford toilets
- Replaces 02125
CRACKED WATER VALVE
A leaking water valve could allow water to continue to flow into your toilet bowl, causing it to overflow. Check out this video from RV Living Yet to show how a water valve in a Dometic RV toilet is replaced.
A Dometic Sealand water valve kit consists of the following components:
DOMETIC 385311641 Sealand Water Valve Kit , white
- Includes water valve, hose clamp, fasteners and instructions
- Package Dimensions: 12.7 L x 2.54 H x 10.414 W (centimeters)
BAD VALVE SEAL/FLUSH BALL SEAL
The “valve seal,” sometimes known as the “flush ball seal,” is the seal inside the toilet bowl that keeps water (and other contents) until flushed… AND it prevents odors from entering your RV’s living space from the black tank below.
DOMETIC (385311658 Flush Ball Seal Kit
- Includes seal and instructions only
- Package Dimensions: 0.254 L x 16.764 H x 14.224 W (centimeters)
CRACKED BOWL
An RV toilet with a plastic bowl is more likely to experience this issue. It’s possible that a small crack has formed in the bowl, allowing water to run out during usage.
Dometic 302320081 320 Series Standard Height RV Toilet, White
- Deep, 100% Vitreous Ceramic Bowl | Full-Size Residential Style Wood Seat
- Dimensions – 22” L x 14.75” W x 19.75” H | Weight – 36.99 lbs. | From the centerline of the bolts to the back of the base at the bottom…
LOOSE OR CRACKED FITTINGS
New fittings would be required here, or you may simply re-wrap the existing fitting/fittings with new Teflon tape and tighten the fitting.
What is the most common cause of a leaking RV toilet?
A faulty flange seal is the most prevalent cause of leaks in RV toilets.
The rubber ring that connects your RV toilet to the floor is known as the flange seal. This seal, also known as a closet flange seal, is comparable to the wax seal found beneath your home toilet. This seal can fail over time due to movement during driving and flexing from the weight on the bowl.
The first thing you should do is double-check that the bolts that hold the toilet to the floor are secure. Loose bolts could be the source of your “leaking flange seal.” If that doesn’t work, and your problem is that your toilet leaks at the base when you flush, you probably have a faulty flange seal. Let’s have a look at how to replace it in a do-it-yourself manner.
What is the procedure for replacing the flange seal on my RV toilet?
The following elements are required:
- Replacement flange seal – this one fits a standard 3” ring:
Thetford 33239 Closet Flange Seal, Gray
- Closet flange for Thetford toilets
- Replaces 02125
- Socket set or wrench
- Towels
- Putty knife or utility knife to remove the old flange seal
- Teflon tape
- Rubber gloves
- Cleaning supplies
Follow these steps to replace the old flange seal:
- Make sure that the water supply to the toilet (and/or RV) is switched off, as well as the water pump.
- Disconnect the water supply to the toilet (find the water pipe and unscrew it to remove the water line from the toilet)… It’s most likely tucked away under the toilet.)
- Locate and remove the bolts that hold the toilet to the floor. Remove the toilet from the floor by pulling it straight up.
- Find the old flange seal and remove it. (It’s possible that it’s trapped at the bottom of the toilet.) To prevent odor, remove the existing flange seal and use an old rag or plastic bag to cover the sewer opening.
- Clean the toilet bowl’s bottom and the area surrounding the sewer ring thoroughly.
- Replace the toilet flange seal with a new one.
- Remove the bag or cloth from the sewer hole and carefully lift the toilet onto the flange seal, making sure it is aligned with the bolts.
- Use your tool to replace and tighten all of the bolts that secure the toilet to the floor.
- Reconnect the water supply and flush the toilet a few times to check for leaks.
What’s Wrong With My Travel Trailer’s Toilet? When Water Doesn’t Stay in the Toilet Bowl, What Should You Do?
If water does not remain in the bowl between flushes, the valve seal is broken (also referred to as a flush ball seal). When you peek inside the toilet, you’ll notice a black seal. Its job is to close the blade valve that keeps the water in the bowl from flowing into the black tank and to open it to let the water out.
These seals can dry out and fracture over time, causing water to flow out of the toilet bowl (and/or aromas from the black tank to enter the bathroom). To avoid this, apply a conditioner/lubricant to the valve seal on a regular basis to maintain it running smoothly and prevent it from drying out.
- [VERSATILITY]: Thetford’s RV Toilet Seal Lube & Conditioner works with all permanent or portable toilets found in RVs and boats
- [FUNCTIONALITY]: Penetrates the toilet seal, lubricating and protecting
This valve seal/flush ball seal is an example, but it might not suit your RV toilet. You’ll need to double-check the make and model of your RV toilet before ordering the right seal.
DOMETIC (385311658 Flush Ball Seal Kit)
- Includes seal and instructions only
- Package Dimensions: 0.254 L x 16.764 H x 14.224 W (centimeters)
How Do I Replace My RV Toilet’s Valve Seal/Flush Ball Seal?
To access the valve, the standard procedure for changing the flush ball seal is to dismantle the toilet. For the exact technique for your make and model, consult the owner’s manual for your RV toilet. Here’s an example of a valve seal replacement on a Thetford toilet from our friend Brian of RVwithTito.com:
Some RV toilets, particularly newer Dometic toilets, allow you to change the flush ball seal from above without disassembling the toilet, making the repair considerably easier.
Why Would a Top-of-the-RV-Toilet Leak?
If the toilet is leaking from the top during the flush cycle, the vacuum breaker’s float seal may be broken. In this situation, you may be able to purchase a float seal replacement kit or disassemble the current float seal mechanism to carefully clean it.
Let’s take a closer look…
What Are the Signs That My RV Toilet Vacuum Breaker Is Leaking?
The vacuum breaker in your RV toilet can leak due to age or wear and tear. The problem could be the toilet’s vacuum breaker if water is seeping from the upper area of the toilet, especially if the rear of the toilet is wet.
Note that the float seal can also leak from the same location, so you’ll need to figure out if the leak is coming from the float seal or the vacuum breaker. Look inside the toilet bowl to do so. If the float seal is the issue, it’s likely to be broken, dried out, or otherwise damaged. If the float seal appears to be in good condition, the water leaking from the upper area of the toilet is most likely due to a faulty vacuum breaker.
What to Do If Your RV Toilet Vacuum Breaker Is Leaking
- The model / serial number of your RV toilet can be found on the bottom of the toilet. Although certain parts are universal, knowing your toilet’s make and model number will assist you in ensuring that the parts you order will fit your toilet.
- Turn off the toilet’s water supply (but have a towel on hand for any excess water).
- Loosen the hose clamps on the hose that links the toilet to the supply line near the foot pedal valve.
- Remove the vacuum breaker by sliding the hose off.
- Locate the rubber grommet that connects the vacuum breaker to the toilet and pry it off with your finger. (Pull out the rubber grommet by sticking your finger into it.)
- Clean the area thoroughly.
- Insert the replacement breaker and replace the rubber grommet.
- Reconnect the hoses (new hoses may be included in your kit) and switch on the water supply.
- Flush the toilet to check for leaks.
When the bowl of my RV toilet is full of water, what happens if it leaks?
This could be a sign of a cracked toilet bowl, especially if you have a plastic toilet. Plastic toilet bowls are more likely to crack than porcelain bowls.
Check the connections behind the toilet to make sure they aren’t the source of the leak.
If the toilet bowl is damaged, you’ll need to repair the entire toilet (and perhaps you’d prefer to replace your regular RV toilet with a composting toilet instead?).
You might also want to read these RV Tips and Guides:
- Thermal Runaway: What Is It?
- Cleaning and Dumping an RV’s Black Tank
- Camping Ice Makers: The Best Portable Ice Makers
- How Tall Is A Typical Fifth-Wheel Camper?
- Is It Possible to Recharge a Camper’s Air Conditioner?
