Why won’t my RV toilet hold water (with fixes)?

Why Won't My RV Toilet Hold Water (With Fixes)

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The toilet in your RV is VERY important, and, of course, one of the many great things about camping with an RV versus tent camping. It’s also something that is very easy to take for granted. Until something goes wrong that is.

Usually, after it has been flushed you RV toilet will hold a small amount of water in the bowl. Less than your toilet at home, but just enough to block odors from rising from the black water tank and entering your rig’s cabin.

When your RV toilet stops holding water it’s a (stinky) problem. But why won’t your RV toilet hold water? And what can you do about it?

An RV toilet bowl not holding water is a more common problem than you think and if you’re  a member of any RVing Facebook group, I’m sure you’ve seen a post where someone is desperate for some advice.

Here’s one. This person’s RV Dometic toilet bowl won’t hold water. I pulled it from Facebook just last week. 

Facebook group chat room on rv toilet bowl not holding water

Some did their best to give advice based on their own personal experience. 

So what really works and what doesn’t? 

An RV toilet works in a fairly simple way.

There are a number of different models available from several different manufacturers, but by far the most commonly used RV toilet is the Aqua Magic by Thetford. You may find different brands installed as standard in some higher end RVs, but the vast majority of RVs on the road in the US are fitted with an Aqua Magic toilet, so that’s the example we’ll be referring to here.

As you can see, an RV toilet is a fairly simple device. This example diagrams the Aqua Magic, but the alternatives are set up and operate in the same way:

Aqua Magic V Foot Pedal Flush

Key No. Description
1 Seat and Cover Assembly - White
Seat and Cover Assembly - Parchment
2 Water Module Assembly
3 Flush Tube and Nozzle Assembly
4 Water Module Link
5 Pedal - White
Pedal - Parchment
6 Foot Cable
7 Closet Bolt Package
8 Hand Spray Kit - White
9 Blade Seal
10 Universal Bolt Cap - White
Universal Bolt Cap - Parchment

With a toilet this simple there is not a lot that can go wrong. A common question I hear around a lot is “Why won’t my rv toilet bowl hold water?” When your RV toilet bowl no longer fills with water, something has gone wrong.  

But what?

In most cases your RV toilet is being left without water because the blade seal, which is a simple rubber seal, has perished, become damaged or has hardened to the point that it no longer works.

The failure of your RV toilet’s blade seal means that water is no longer held in the toilet because the mechanism isn’t working anymore. Solving this issue is deceptively simple; switch out the old and damaged blade seal for a new one.

In the next part of the article we’ll go over in detail of how to fix a RV toilet that won’t hold water.

How to fix a leaking RV toilet seal?

If you are relatively handy, and don’t mind the idea of taking your RV toilet apart replacing a blade seal is a relatively straightforward job, but if you are not sure that your DIY skills are up to the job there’s no shame in calling in a plumber to help, as an improperly repaired RV toilet can lead to all kinds of problems.

If you do feel comfortable with taking on this repair task then the first thing you need to do is buy the right RV toilet repair supplies, including that all important new RV toilet blade seal.

Choosing the right RV toilet repair kit

Remember we told you that most RV toilets are a Thetford Aqua Magic model? There are several different models though, and it’s not a given that your RV toilet is. Therefore the first thing you need to do is determine just what type of RV toilet you have installed.

Ideally you still have the manuals that came with your RV somewhere to hand, in which case this will be an easy task. If not, you may be able to see the model number near the base of the toilet itself.

You will find that they sell the blade seal you need in many of the hardware stores that stock RV parts or you can head online to Amazon to find the piece you need. It will usually cost somewhere between $15 and $25, a nice surprise as often when their RV toilet will no longer hold water RV owners worry that they will be faced with a very expensive repair.

How to replace RV toilet bowl seals:

To replace seal:

1. Turn off the water to the toilet and flush it to empty the toilet bowl and relieve any remaining water pressure.

2. Remove the bolts that hold the toilet to the RV floor. There are two, one at either side of the toilet.

3. Disconnect the water pipe at the back of the toilet

Disconnect water supply from RV toilet

4. Carefully lift the toilet up and off. Place it somewhere safe, away from the area you are working in.

5. Put a rag across the exposed waste hole. This will help shield you – and your RV- from the possibly pungent odors from the black water tank.

6. Locate the seal, which is a simple rubber ring, remove it, and replace it with the new one.

Replace seal on RV toilet bowl

7. The seal should come with specific instructions for doing this for your particular model of RV toilet.

8. Before you start the process of replacing the toilet add a small amount of water to ensure that the new seal is now holding water in the way it should be.

Extra Tip: Most seasoned RV owners also recommend that you add a new rubber seal between the floor flange and the toilet at the end of this repair.

9. Carefully reinstall the toilet, making sure that the bolts are properly tightened.

10. Turn the water back on and test flush.

A bad blade seal is a fairly common problem, as these seals do not last forever.

Fortunately, as you can NOW see it is not a difficult or expensive fix

If you are more of a visual learner this short video walks you through the repair we just described as it is performed on a standard Thetford Aqua Magic toilet:

Other causes of RV toilet not holding water

Broken RV Toilet Water Valve

In terms of RV toilet problems related to wear, tear and age there may come a point when you will need to replace the water valve in the toilet. You’ll know this is the case if you flush your toilet and the water continues to run beyond the point you would expect.

A broken RV water valve is often the result of the piece having frozen and thawed again, so to prevent this try to make sure that your RV is parked up somewhere away from harsh winter weather.

Fortunately this is also a simple fix and a new water valve can be purchased inexpensively as well. 

This video explains the process very well.

Broken or Worn RV Toilet Flange

A broken RV toilet flange can affect the function and the stability of your toilet and is a common cause of leakage around the base of your toilet.

Worn RV Toilet Parts

Most of the parts in your RV toilet are either rubber or plastic, so they should last for years. Should you ever need to replace one due to wear most of the individual components are easily available online.

Can I upgrade my RV toilet?

As we mentioned, most RVs come equipped with a Thetford Aqua Magic toilet. However, we have also mentioned that there may be a different model in high end RVs and campers and you may have wondered what we meant by that.

If you want to upgrade your RV toilet there are an increasing number of options available.

Thetford, Dometic and other major RV toilet manufacturers all offer china models that are more like a domestic home toilet. Many of those also have a higher profile which some people find more comfortable to use.

There are also accessories that can be added to an existing RV toilet to upgrade them. For an example a bidet seat attachment can add a ‘spa’ touch without the need to replace the whole unit.

Final Word

An RV toilet is an important part of your camper and of the camping experience as a whole, so a broken one can ruin a trip. Hopefully, you now have a better understanding of why your RV toilet stops holding water and what you can do to fix the problem as well as of the way an RV toilet functions overall.

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