No, it’s not because you hit up the Taco Bell midnight menu or, well, maybe that’s part of it. If your RV toilet is leaking at the base, that’s something that will skyrocket to the top of your to-do list in a hurry.

There are a lot of reasons behind an RV toilet leaking at the base, including fractures in the toilet itself, the base is no longer properly sealed, a misaligned supply line issue, or a messed up water inlet valve that’s either cracked or deficient in some way.

With all of that being said, you can’t fix it until you locate the problem. The last thing that you want to do is jam your head down in there and get a bird’s eye view of the potential cause. So, you want to start from the outside and work your way in, especially if the toilet has been used very recently.

Keep in mind that you may not have a leak at the base of your RV toilet. It may be that the inlet water hose is leaking and the accumulation of water on the floor, around the base of the toilet, indicates that there is a leak at the base. It’s worth checking out as well.

If you’re looking for a new toilet for your RV, we’ve written an entire article on the 5 best and most reliable toilets for an RV.

Fixing a leaking RV toilet

The first two things that you need to eliminate are the possibilities that you either have a leak from the inlet water hose or your base is simply loose at the bottom. Everything gets more difficult from here so you don’t want to go there if it turns out that you don’t have to.

Inlet water hose

This is the hose that comes in the back of the toilet and provides that little bit of water whenever you flush. You can check it by reaching your hand around to the back of the toilet. Feel all around the connection point where the hose screws into the receiving end of the toilet.

If you feel any moisture, that’s an indication that you may have a leak. If you can, flush the toilet and keep your hand on that inlet. If you feel water coming out, you have your culprit. Fixing this is quite simple unless it’s cracked:

  • Unscrew the plastic cap connecting the inlet hose to the toilet
  • Completely dry the threads on the receiving pipe
  • Use a paper towel or a dry rag to dry the threads inside of the screw-on cap
  • Use PTFE tape around the exposed, receiving end threads
  • Wrap it several times until you have a good amount of coverage
  • Screw the cap that connects the inlet hose back onto the thread

That should deal with your seal, however, if any of the pipes that come together is cracked or worn severely enough to where it has trouble catching the threads, the entire mechanism should be replaced.

Tightening the toilet fastening bolts

Sometimes, your RV toilet may spring a leak at the base and you may think all hell must have broken loose down there and you will have to replace the entire contraption. But, it’s really just the bolts that hold the toilet hard to the deck that has come loose over time.

That happens when you sit on an RV toilet a lot over the years. Even the tightest of bolts will loosen up over time. Of course, the only way to know this for sure is to test your theory out:

  • Make sure that the base of the toilet and surrounding area are completely dry
  • Locate the caps that cover the bolts (one on either side of the toilet)
  • You will either have to lift a plastic cover that wraps around the toilet or remove individual, plastic caps off to reveal the bolts
  • Tighten each bolt down, giving it plenty of torque but don’t pop a vein over it
  • Flush the toilet and look for signs of water around the base

Last but not least, you’ll want to run a light across every surface of the toilet, checking for cracks throughout. You’ll need to check both inside and out and try moving the toilet around a little, as the pressure of the movement may reveal the crack.

You want to eliminate the toilet’s bolts, potential racks, and the inlet valve first because the rest involves a lot more work and you may have to drain your black water tank.

Hopefully, it won’t get to that point but it’s best to prepare for the worst and hope for the best. There are three more things that you are going to check next, or possibly two, depending on the type of toilet that you have installed.

The ball seal

The ball seal is only a possibility because not every toilet has one. While water may be leaking out on your floor, it’s primarily because the ball seal isn’t holding the water and it’s leaking down and out through a compromised flange.

Ball seals are an easy replacement, at least compared to the flange gasket. You will need to put on some industrial-level biohazard gloves. You’re going to reach into your toilet and mess around the seal directly in the hole that opens when you depress the valve. Here’s how to fix the problem:

  • Depress the water valve
  • The ball slides out of the way leaving an open hole
  • Reach through the hole and pull the ball seal out
  • It usually comes out pretty easily
  • Lubricate the bottom of the new seal
  • Replace the seal with the valve still closed, working the seal around the ball

You might as well do this since you’re about to disassemble your RV toilet because the ball seal should be as new as the flange gasket.

Replacing the water valve

Before you do anything that involves removing the toilet, shut off the water supply to your RV, open up all of the faucets inside and allow them to fully drain, and flush the toilet over and over until no more water is flowing through from the inlet pipe.

Also, bring plenty of towels into the room with you. The toilet is the lowest drainage point in the RV so you’re still going to get water everywhere even with it shut off.

This is almost as easy as replacing the ball seal, except for the fact that you really should take the toilet out before you replace it. Some toilet designs may accommodate you enough so that you can replace the foot valve without removing the toilet but that’s a rarity.

If your water valve is leaking, you’re not going to be able to differentiate between it and the flange gasket on the floor, as the valve is usually located right above the floor. A slow leak will simply go undiscovered. Make sure you have a decent socket set handy.

  • Locate the bolts on either side of the toilet and remove the plastic covering
  • If the plastic covering is clamped on pretty tight, use a flathead screwdriver to pry it up
  • Remove both nuts holding the toilet to the bolts
  • Lift the toilet straight up and off of the bolts
  • Use toilet paper, aluminum foil, or a rag to cover the hole because it’s going to smell
  • Use a putty knife or a wide flathead to remove the flange seal if it doesn’t want to come off willingly
  • Clean everything thoroughly and then clean it again
  • Replace the original flange with the new one
  • Remember to remove any paper towels, toilet paper, or aluminum foil that you placed over or pushed into the hole
  • Return everything to its place in reverse order

The reason that you want to clean so thoroughly is the flange not only needs to be seated perfectly, you also don’t want any additional trash or debris (especially if you had to pry the original flange up, piece by piece) that will keep the toilet from sitting flush against the floor when you reseat it.

Replace the toilet and test everything out

Once you have a new flange in place, a new ball seal, and potentially a new water valve, you’re all set and you can go ahead and test out your handiwork to see if you stopped the leak.

If you did everything step by step, including carefully replacing the flange and seating the ball seal, there shouldn’t be any leaks to speak of. Be sure to dry everything up around the toilet so you can tell the difference between a fresh leak and old water from the repair work.

Turn your water supply back on and flush the toilet a few times. If you’re leak-free, congratulations.

Final thoughts

It’s not the cleanest work in the world and hopefully, if you spot water on the floor around your RV toilet, it’s nothing more than some loose bolts or an overly enthusiastic flusher got carried away.

Either way, fixing the leak, even if it’s as bad as needing to replace the flange gasket, isn’t the hardest DIY job in the world, even if it’s not the most appealing one.