Royal Flush

A little care and maintenance will keep your RV toilet on the go

Whether while on the road or in camp, the smell of sewage in the motorhome can elicit panic. Where is it coming from and, perhaps more important, how do I get rid of it?
Most RV toilets are pretty simple affairs, but modern technology has resulted in an uptick in complexity to allow designers to make motorhome floorplans more intuitive and exciting.
Go back far enough in American history, and the most common way to “go” was in the outhouse. Sir Isaac Newton’s flush mechanism, also known as gravity, worked well in the outhouse and is also the preferred method in RVs. The fundamental difference is, in motorhomes, there’s a valve between the tank and the seat.

Diagram of the workings of an RV toiletOK, there are some more differences, like running water to aid the flush, but the concept is similar. In a residential toilet, water flow pushes the contents into a pipe that goes to a septic system or sewer system, maintaining a water barrier between the seat and the termination to keep odors at bay. While an RV toilet may have a small amount of water in the bottom of the bowl, it is there more to aid in the breakdown of solids in the holding tank than to power the flush or to be a water barrier between the tank and the inside environment. That is done via a sealing mechanism.

The majority of RV toilets work on a simple principle (we’ll address the more complex models in a bit). A hand, foot pedal or electric switch is used to add water to the toilet before use. With the former, water is added via a slight depression of the foot pedal or by opening the water valve lever. After the “go,” a full depression of the foot pedal — or activation of the hand flush —opens a valve at the bottom of the toilet, allowing gravity to pull the contents down into the holding tank. The toilet is then ready for the next contestant.

Despite its inherent simplicity, an improperly maintained RV toilet can fail to seal or worse and get stuck in a slightly open position that allows water to flow, slowly causing the black tank to fill then overflow into the motorhome. While this extreme example is rare, just having the toilet not seal properly, allowing odor to get through, is bad enough.

Using the RV toilet properly is the best thing you can do to prevent problems. This means adding at least 1⁄3-½ bowl of water when solids are involved. This does two things. First, it allows the contents to flush more thoroughly and more quickly, reducing the risk of solids getting caught in the flush mechanism. Second, ample water, along with a good RV tank chemical, helps to control odor and breaks down paper and solids in the tank. This helps keep a cleaner tank over the long term. Also, be sure to depress the flush mechanism completely and quickly to open the discharge all the way.

The flush seals are pretty tough material. However, they will wear with extended use, and sometimes lose their elasticity, causing leakage. Foreign debris, which is the easiest to fix, is also a common cause. A right-angled flat blade screwdriver passed around the inner edge of the seal will aid in fixing this issue, as will careful use of a soft toilet brush, like Thetford’s RV toilet brush. If this doesn’t correct the problem, disassembly and cleaning with the replacement of the seals is recommended.

Naturally, there are dedicated products for adequately cleaning an RV toilet. It’s essential that especially caustic cleaners, like many commercially available toilet cleaners, are not used in an RV toilet. The valve mechanisms are made of plastic, along with various rubber or other synthetic seals and parts that may not react well with those chemicals. Stiff bristle toilet brushes are similarly not recommended.

Leaks can also result from a loose flush mechanism or, in the case of some porcelain toilets, a loose attachment band between the bowl and pedestal. Improper winterizing can lead to a cracked water valve, check valve, pipe connection, or toilet body, so winterizing with RV antifreeze is always recommended.

A sticky valve must be fixed as soon as possible. Besides the debris already mentioned, sometimes the seals become dried out and sticky, or the mechanism gets rusty and sticks. A quality valve lubricant like Dow Corning 111 will work well to lube the gaskets and slide valve or ball. Again, if this doesn’t do the trick, teardown and cleaning may be required.
Macerator toilets like the Dometic MasterFlush and Thetford Tecma models require a little more maintenance because of their moving parts and systems.

As in any RV toilet, it is imperative that nothing other than RV/marine toilet paper is flushed down a macerator toilet. It needs to be a paper that is rapid-dissolving. Any other items can cause a jam or worse in the macerator pump, requiring an unpleasant teardown and cleaning to repair.

Occasional flush-cleaning of the macerator is recommended. While ordinary toilet chemical can be used, a specialized cleaner like Thetford’s Aqua-Clean is a better choice. Never pour bleach down the toilet, and don’t use any harsh chemicals, including household toilet cleaners, as they can damage sensitive parts and hoses. There are specialized cleaners on the market that are safe.

Winterizing a macerator or vacu-flush toilet requires a little more care than a gravity flush model because there are pumps and valves in the system that need to be protected. Running RV antifreeze through the complete system is essential.

By following a few steps, and being careful how you use your sanitation system, you can be assured your throne will be ready when needed.

For More Information

Dometic Corp. | 800-366-3842
Thetford Corp. | 800-543-1219



  1. I go on camping/fishing trips where I stay at an RV park or camp ground for 10-15 days. Because I do not move my RV while there, the solids in the toilet dropping down into the holding tank sometimes build up to a mound that can raise up to the bottom of the toilet hole. To solve this problem, I got a 3 foot piece of doweling, screwed a 3” wide piece of flat aluminum plate to the end of the doweling, there by making a “Pooper Scooper”, I hold the foot valve down, and using a flashlight, I guide the aluminum plate down into the holding tank at an angle all the way down to the bottom of the holding tank, and then give it a sideways swing, thereby moving the mound of solids further back into the holding tank. I then gently remove the “Pooper Scooper” making sure not to damage the rubber seals around the bottom of the toilet discharge hole. Simple but effective way to extend my stay without having to pack everything up and drive to the dump site.


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