I've been researching the issue of waste removal (before beginning to convert our 23' foot box into an RV). I've determined this problem breaks down into two categories; wet and dry disposal.
Wet involves a blackwater holding tank while dry involves removal of fecal bulk versus ash. These five solutions (below) encompass the scope of my research.
1. RV-toilet with flapper valve and rubber seal/water pocket
2. Conventional home-toilet with water trap
3. Unconventional home-toilet (macerating) with water trap
4. Electric-toilet, like an Incinolet, equipped with ventilator
5. Composting-toilet, like Loveable Loo using sawdust or kitty litter
While I am sure other solutions will vary in the details, wet and dry cover the basics. Included below are my notes vice odor control and maintenance. Researching this may not have been fun, but it was interesting. Perhaps you'll find it of value.
We all know how a home toilet operates. A quantity of water (typically in a holding tank) is dumped into the toilet bowl, which flushes waste through a p-trap (for odor control). The waste flows through the blackwater line into a public use sewage pipe, or into a septic tank system. Both are considered open systems as subsequently emptying a container is not part of the process. Developed and refined over the course of many decades, these systems work and are reasonably sanitary.
Here are 5 basic methods of disposing of waste in an RV.
1. An RV toilet differs from a home toilet in that waste dumped into the bowl is evacuated via a foot-operated flapper valve, which uses a rubber seal (plus a small quantity of water) to preclude odor from the blackwater holding tank entering the bathroom. This, in combination with a ventilating-fan does an efficient job of keeping the living space odor free.
Unlike a home toilet, instead of waste routing to an open system, waste settles in a closed system, e.g. a blackwater holding tank. The latter is manually dumped and cleaned periodically at a Flying-J, government sponsored rest stop, or commercial RV parking area. Frankly, it's a time consuming and nasty job, which in some cases involves additional expense for disposal. Moreover, the use of special chemicals in the holding tank plus rapid-decomposing toilet paper constitute best practice.
A pretty good overview of the care and maintenance of this type of system is this 15-min YouTube video (a 2-1/2 minute short-video is linked to this one if you're in a hurry).
HOW TO: Dump & Clean an RV Black Tank - YouTube
2. A conventional home-type toilet can be used in an RV as well. Low water consumption models, which use approximately 1.25 gallons are common, inexpensive (<$150), and offer a perfectly acceptable system because they're very easy to maintain since there's no flapper mechanism. An added benefit is you don't have to remember to shut off the ventilating fan to keep from sucking bad smelling air (via the blackwater holding tank's vent) back through the flapper valve and into the bathroom.
There are two obvious downsides, e.g. weight (perhaps an additional 50 pounds) as well as the issue of securing the porcelain holding tank and lid while moving because they're (obviously) not designed to sustain lateral accelerations.
The latter has ready solutions via bracing. The former doesn't strike me as an insurmountable issue because our nominally 22,000 truck, when converted for use as an RV and weighing perhaps 26,000 pounds, has been designed to transport as much as 30,000 pounds of cargo. Simply put, our 26k pounds is only half of the designed gross weight of the vehicle and thus, an extra 50 pound is no big deal (in my view). Not when compared to the convenience of not having to maintain a flapper valve.
Someone will observe this kind of toilet will use more water than an RV-toilet. Maybe yes, maybe no because double flushing is pretty common for RV toilets (and sometimes more often when fecal matter and toilet paper gets hung up on the flapper valve). Meanwhile, modern low water consumption home-type toilets are marvelously engineered devices usually capable of dumping a load with a single flush. An added plus is reduced maintenance since you'll never have to deal with the rubber seal on a flapper.
3. An unconventional home toilet is an interesting solution in that it features a macerating pump as well as a conventional p-trap to control odor. The principal advantage is dumping the backwater tank is easier because waste has been liquified. The downsides include weight, cost ($800), plus the porcelain tank/lid issue of the conventional toilet. Here's a manufacturer's link, which includes a very good video. I rather like this versus a conventional porcelain home-toilet.
Installation of pumps, grinders, and toilets for the home | SFA
4. An incinerating toilet is favored by some. The chief advantages are reduced system complexity (blackwater tanks are not merely heavy but relatively complex to operate and maintain - and don't forget, nasty). For many (us included), simply not having to deal with dumping and cleaning a blackwater holding tank is a big deal, e.g.the attraction of a dry system. FWIW, the brand I researched is an Incinolet.
Downsides are the electrical load, which requires operating the genrator for about an hour each time the cycle begins, cost (~$2000), the aforementioned cleaning, and other issues related to maintaining the system, which aren't readily apparent on first inspection.
For example, using one of these incinerating toilets is easy enough. They feature a liner inserted into the box below the toilet seat (think litter box liner) into which waste is collected. After which, a foot-operated valve simply opens a trap door and drops the load into an incinerating chamber where, for all intents and purposes, electric elements like those in a toaster or space heater accelerate drying/burning to produce ash for subsequent disposal. Not mentioned are what happens when the liner leaks or or otherwise smears fecal matter either on the sides, or on the trap door. These are not inconsequential issues because as we all know, shit happens!
Anyway, this sounds like a slick system - if you can stand the cost plus the ash. The latter, however, may be an issue over time. Also, related to cleaning, is disposal of heated air to preclude odors. This is because, as you might imagine, cooking down a pile of shit doesn't produce a pleasant smell. Basically, the system vents through a 3-4" diameter insulated pipe vented through the roof much like that used for a wood burning stove. I found this video interesting because it cooled my ardor (pun intended) for an incinerating toilet due to ash collecting in the vent pipe. The video also gives a very good idea of maintenance considerations.
Incinolet Toilet the poop Incinerator that got plugged up the ash - YouTube
5. Another dry toilet is referred to as composting-toilet. Basically, you're defecating into a 5-gallon bucket and subsequently covering the poop with sawdust or kitty litter to control odor. Anyone with an indoor-only cat knows this works (if you don't let the turds build up too long). An example of this is a Loveable Loo.
This is an interesting alternative to toilets 1-4 above. Benfits include cost (a couple hundred bucks plus shipping), weight (the whole thing surely won't exceed 100 pounds including litter supply and spare buckets with lids versus hundreds of pounds for a blackwater system). Simplicity is a benefit too because dumping the bucket, or more accurately reflecting what I think we'd really do, bagging the turds for disposal, is easy. Some may actually dump them into a compost pile (not really our thing) however, we more likely would seek out an available dumpster. Here's a nice video, also on YouTube, of the Loveable Loo (version 2) in action (so to speak).
How We Make the New Loveable Loo® - YouTube
Wet systems are complex, expensive, and nasty to maintain. Dry systems, like an Incinolet are expensive, complex to plumb, and nasty to maintain as well (regardless of what propnents may suggest).
I've decided a Loveable Loo-type dry-toilet is best for us. Probably home-made too since, unfortunately, they don't offer a long bowl option (women generally prefer a long-bowl toilet seat because it affords easier access for cleaning up after urinating). However, I have asked them to investigate making a long-bowl toilet seat version because I'd just as soon not take my time to reinvent the wheel (though I am handy and wouldn't have any trouble whatsoever whipping up a wooden box to hold a 5-gallon bucket plus a toilet seat). Moreover, and quite frankly, I have other things to do (that, and I just like to reward enterprising folks like these, whom are making the Loveable Loo).
Finally, an added advantage of this dry system (if it ultimately doesn't suit our style, for whatever reason) is we can always fork over the dough to install a wet system, or an Incinolet, later . . . without much of an economic penalty.
In closing, I welcome your thoughts and comments.
John Beech - GM