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July 26, 2022

TT# 132 RV Macerator Toilets and Waste Systems, and Water Distribution Control

By: Rob Lowe

Featured Picture

Macerator Toilets

More and more RVs include a Thetford or Dometic macerator toilet that uses a turbine pump style of macerator to chop up any waste and pump it to the black holding tank. For those that have been RVing for many years, the question often arises: "Why does my RV have this style of toilet”? Some find the short time when it does the macerating to be noisy and are cautious about flushing it when others are sleeping nearby.     

 

I’ll answer the question, then walk through some of the benefits to this style of toilet, then look at waste management systems that use the same principle.

 

In larger RVs there is often a half bathroom that can be in varying locations around the coach, as well as an ‘ensuite’ style of bathroom located adjacent to the rear bedroom. With gravity toilets the waste drops directly into the black tank or travels a short distance to the tank. This reality limits the location of toilets (and bathrooms) as well as the size of the waste tanks that can be installed in the RV. Good design and engineering suggests that the waste tanks be where there is sufficient weight carrying capacity. That location might not be in the best location for a practical RV floorplan. Generally, the fresh and waste tanks are located ahead of the rear axle of the RV so that the weight of the fluids is supported by the RV between the front and rear axles. This also allows larger tanks to be grouped together for easy access to them for filling and emptying all together. The ability to place the toilets directly over the black tank is often difficult.

 

The challenge of locating a toilet where it optimizes the floorplan thereby making it convenient for the user, is solved with the installation of a macerator toilet, that liquifies the waste and pumps it into the waste tank. The toilet is installed in a practical location and the waste tanks are in the best location for load carrying and convenience for dumping. A macerator toilet makes it a technical possibility to have a bathroom in a slideout. This increased flexibility in design explains why there is a macerator toilet in one location within the RV, and a conventional toilet in another bathroom in the same coach.

 

As with all equipment in a RV, there are some user guidelines that should be followed. Read the Toilet maker’s owner’s manual that came with the RV (or access it online) to ensure you know how to use it and do what is expected. The term macerating is defined as: "cause to grow thinner or waste away”. In earlier versions of a RV toilet this process took place with a series of fast revolving blades that chop the waste into small pieces that when mixed with water became quite easy to pump or move. Newer RV macerator toilets combine the functions into a single macerating pump. They utilize a turbo pump located withing the toilet that macerates the waste and pumps at high speed, the wastewater slurry into the Black tank. All makers recommend using RV toilet paper (typically thinner one ply) and avoiding excess amounts. Nothing should be placed in the toilet that will damage the turbine pump, thus all paper towels, moist towelettes or feminine sanitary products should be tossed into the trash and not into the toilet. Sufficient water should be used to flush the toilet. Adding water into the bowl prior to use, ensures that waste is macerated and can be pumped into the black tank. Any warning lights about the ability of the toilet being able to operate, should be heeded. If a warning light is on, the toilet will not function, since often the light may be warning that the black water tank is full. If it is not, then sometimes the warning light is on due to a poor (corroded) electrical connection, that creates the warning light indication. These connections can be cleaned and protected by applying an anti-corrosion spray (such as Corrosion Block®) to the connectors at both the toilet and the panel where the warning light is located. The owner’s manual often has troubleshooting hints that should be followed.

 

RV Macerator Waste Systems

Many newer RVs are equipped with Thetford’s Sani-Con waste management systems. These systems eliminate the need for a 3” (7.6cm) collapsible hose (aka ‘the stinky slinky’) and dealing directly with hose connections to the RV and the dump station each time. A Sani-Con uses a sealed 1” (2.5 cm) inner diameter hose that is permanently attached to the pump and the dump station connector. This connector can be easily threaded into a 3” (7.6cm) or 4” (10cm) station fitting, or if there are no threads on the dump station fitting, then the tapered part of the connector can be pushed into the station’s pipe fitting. At the bottom end of this connector is a small threaded fitting and cap designed so that after removing the cap, a conventional ¾” (1.9cm) garden hose can be connected to it. The Sani-Con can pump uphill or using a garden hose to move waste much farther from the RV than possible with a length or two of regular RV dump hoses.

 

The primary concern I’ve heard is that using a Sani-Con takes longer to move the waste. Offsetting that perception is the fact that the hose remains connected to the RV, and it is simple to remove from the storage area and connect to the dump station fitting. The Sani-Con, its hose and fittings are rinsed during the dump process. No need to remove and disassemble the large hoses and store them again, every time the tanks are dumped. Adding the time to take out, connect the hoses and dump with a 3” (7.6cm) dump hose, then flush and clean the hose(s) then disassemble and store, makes the dumping process time very similar. With a Sani-Con there is the added benefit that there is far more flexibility in where to dump the RV waste tanks into approved dump facilities, even toilets. Many prefer using the Sani-Con. Thetford has introduced a Sani-Con Turbo that greatly increases the dumping speed and lengthens the horizontal distance to dump, up to 150 feet (45.7m).

 

I was in the group that did not see the need for such a system, until the RV we purchased had one included. After adjusting to using it, I’m solidly in the Sani-Con user camp. I find it more convenient, clean, virtually odor-free and efficient. Of course, all users need to avoid placing anything that could damage the turbine into the sinks or toilet, however that is almost a non-issue for us.

 

A Water Manifold Makes Hose Connections Easy!


Water ManifoldOn this RV, it was simple to plumb in a multi shut-off manifold to direct water to where it is needed. One shut off directs water from the incoming water hose (Green arrows) to the RV freshwater inlet (Yellow arrows). Another connection feeds water toBlack Tank Flush water connection a black tank flush fitting (Red arrows). For safety, a backflow prevention device (see Double Blue arrow) is incorporated in this water line to eliminate any risk of water contamination from the waste tank flush water backflowing into the water lines. The water in this prevention device and associated water line drains to the floor of the compartment when the water pressure is reduced as the water control valve is turned off. Black Tank Flushing is simply a matter of rotating a shut-off valve to direct water to the connection feeding the tank flush line when needed. Two additional connections are left capped; should water be needed somewhere else, it is simple to remove the cap, attach a hose and control water flow with the associated valve.

Using this system combined with the Sani-Con eliminates all hose handling when dumping, thereby preventing cross contamination of the fresh water that can occur from handling the wastewater hoses and then the freshwater hoses. The water manifold allows one incoming RV water hose connection to distributed water to all necessary places in the RV. Since all other connections are permanent, an incoming water hose with quick-connect connectors on it, makes it simple to connect or disconnect the hose and the manifold makes it very efficient to move water where it is needed. Note: The second photo shows the incoming water hose being directly connected to the manifold. On this coach the location of the Coach water inlet presented clearance issues that made it difficult to connect the freshwater hose directly below the manifold when the manifold was installed. By installing a short hose that extends below with the quick connect fitting on it, the water supply hose can easily be attached to the manifold using quick connect fittings. This setup allows water to be connected and easily distributed throughout the various places where water is needed.

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