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Planning to build a traveler's trailer from a cargo trailer and was thinking about various toilet setups. I don't care if the trailer looks awful as long as it's cheap and easy to build.

I'm ruling out the composting toilet. I've seen some freezing toilets on the web, but I can't help to ask myself one question:

Why can't you have a bag over something similar to a conventional toilet and then dump it in the freezer each time you use the toilet?

Then when considering the flushing toilet + a wastewater tank, what's the minimalistic setup possible?(cheap and easy to build)

closed as too broad by Ed Beal, Daniel Griscom, ThreePhaseEel, Tester101 Feb 16 '17 at 15:12

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    Go buy an old trailer and fix it up. It will come with a crapper, sink etc, including holding tanks. Starting from nothing is a waste of time. – d.george Feb 14 '17 at 20:27
  • Carry a folding chair with a hole in the seat. Go in a bag and keep it on the drivers seat next to you until you get to the next dumping station. Get real ; go buy a used trailer that is already set up properly – d.george Feb 15 '17 at 11:15
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Here in the UK, we always use chemical toilets for this sort of thing. They have a removable waste tank built in that in many models can hold at least a person-week's waste, and the chemical keeps it from smelling for that long even in hot weather. The capacity lasts a lot longer if you don't use it for everything. Emptying can be done into a normal toilet (e.g. at home) or at an emptying point for RVs, and the chemical additive is available in a type suitable for septic tanks. Most use a cassette tank that's removed through a hatch on the outside of the vehicle.

I'm sure you can buy the chemical in the US, whether the toilet is available is another matter. Brands over here include Thetford and Porta-Potti. They're usually made of plastic so are much lighter than a domestic toilet, and also use much less water to flush.

  • Apparently UK has a thing called an "Elsan" which is a mini-dumping-station specifically for cassettes from portable toilets (many made by Elsan). They go to sewer mains (the chemicals would poison a cess/septic). – Harper Feb 15 '17 at 20:42
  • An "Elsan (emptying) point" is the drain. I stayed in my camper van on a site without mains drainage quite a lot last year. There were no restrictions on emptying the toilet. In fact the chemicals are intended to break down solid waste, and the bottle I have says it's OK for septic tanks (@Harper). Is there really nothing like this in the US (location guessed from the wording in the Q)? – Chris H Feb 15 '17 at 21:09
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    America has cassette toilets, but not dump points specifically designed for cassettes like an Elsan point. People seem to dump into toilets, mostly - often by stealth. Our chemicals are nasty (but cheap), and a lot of septic-based dump sites have been closed after cassette toilet chemicals contaminated groundwater. For a few extra dollars you can get "alternate" chemicals compatible with septic. – Harper Feb 15 '17 at 23:13
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Resources:

This is a hard problem

When they developed the A-10 Warthog, they started with the enormous, tank-killing cannon. Then they built an airplane around it. If you want a decent toilet in a small travel trailer, it's a lot like that: the water and sewage system dominate the design.

So if your notion is "leave a 24 inch square space for the toilet whatever", you'll need to do some more design.

Human feces is toxic and spreads disease (particularly human disease to an extent animal feces do not). So you must dispose of it properly. There are "dump stations" all over the world to allow RVs to dump their blackwater and graywater tanks. Anywhere there's a canal system, there are dump stations for the boats too. Human waste is never dumped into the environment. That is literally a crime, and you will go to jail and/or fined severely if caught. By "fined" I mean pay the actual cost of a hazmat response. Not cheap.

Everyone - aircraft, trains, military ships, even ocean liners - have holding and retention tanks.

Ask the people doing it

This is widely done in several DIY communities: Tiny House builders, VanLife people making vans into RVs, off-grid communities (who are often borrowing land or using land that won't perc for septic), RVers of course. You could spend many evenings browsing what they have to say in Youtube, podcasts and blogs.

The English have an equivalent: narrowboats on their amazing canal system. They are very economical as primary residences, except for the crushing $200-1000/month for a permanent mooring with hookups. So, many cut the cord and "continuous cruise" the system, tying up anywhere, effectively boondocking 24x7. They have answers too.

The upshot is there are no silver bullet solutions. There are several lead-bullet solutions.

Flush toilets are problematic

A residential flush toilet has two serious problems in a vehicle. Consider how it works in a house. The clean water in the bowl is part of a trap, just like the one under your sink. This "slug" of trapped water keeps sewer gases blocked. This wouldn't work if vacuum or pressure developed in the sewer pipe to suck or blow it out, so the sewer pipe must be vented to the roof to equalize pressure. In a vehicle, the water will splash out of the trap. The vent will smell, and may act as a pitot tube in motion, creating the pressure/vacuum the stack is meant to prevent.

A couple other problems with flush toilets is they use an awful lot of water, which makes your blackwater tanks a lot bigger and/or your endurance a lot shorter. You must also have potable water to flush with, you can't use greywater.

Freezing will make more problems

I have never seen the "freeze it" solution. It seems like you'd have an unresolvable disposal problem. There are many places to do a proper RV cleanout, but all are designed for liquid waste and would not be able to accommodate a frozen brick of poop-water. Pretty hard to dispose of.

  • You just won the "First time anyone said 'frozen brick of poop-water' on StackExchange" award. – gregmac Feb 15 '17 at 16:10
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One option you may consider is that of an incinerating toilet. Usually run on propane or natural gas, they are about as minimalist as you'll find. Not necessarily minimalist in price, but compact enough to be useful for the application you describe. I used The Google to search for those two terms and found a deluge of responses.

There's almost nothing to cover the DIY aspect, however. I can envision a suitably insulated enclosure, perhaps using firebrick as well as a suitably insulated separator to keep the user from getting an overly heated bottom, followed by the necessary burner and igniter assemblies.

Of course, playing with explosive gasses and enclosed spaces doesn't really fall into the DIY category, does it?

  • One caution on incinerating toilets. Find one to clean before you buy. I have worked on an electric model on a buddies fishing trawler. He could not give me enough salmon & halibut to do it again. OK he is a really good friend and I would for him but he would have to do some serious begging. – Ed Beal Feb 14 '17 at 20:50
  • I'd expect the temperatures in an electric version are lower than that of the gas burner type, yes? The gas burner type is purported to reduce the waste to easily removed ash. It's always good to hear from someone with an experience, good or bad! – fred_dot_u Feb 14 '17 at 21:12
  • The electric's do reduce the waste to ash until something goes wrong then what a fowl mess. I am sure the gas fired ones have similar problems and work ok most the time. The greenhorns usually get the clean up job(s) and it had been "cleaned" but the "residue" was just nasty. Much worse 100x than changing a wax seal in a conventional toilet. – Ed Beal Feb 14 '17 at 22:45

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