Top 10 things to know before buying a composting toilet

Top 10 things to know before buying a composting toilet 

Separett Composting Toilet

Separett Composting Toilet

Gain important knowledge, and avoid buying the wrong composting toilet.
  1. Will it stink inside? Absolutely not, as long as you have a toilet with a vent and fan. The fan draws air into the toilet, and exhausts the stinky air outside. It should never enter the bathroom area.
  2. Will it stink outside? There can be a bit of odor where the vent terminates the home. This is less with a urine diverting toilet. The vent should not terminate near a deck, door, or opening window. If in doubt, run the vent up to the roof line. Do not believe anyone that tells you that you don’t need a vent. There is moist, stinky air in that toilet and it MUST go outside.
  3. How much does a good composting toilet cost? You should expect to pay between about $950 and $2000 for a high quality composting toilet with a vent and exhaust system.
  4. Is it legal? Probably, but legality varies widely. Usually, permits can be obtained (if necessary) by approaching senior managers at the county office. Inspectors generally can’t approve them, because it’s not in the code book. You can read my detailed post on the subject here. Are Composting Toilets Legal?
  5. Is it a urine diverting design? The better toilets separate urine from solids. Urine is practically sterile, and very easy to dispose of safely. Solids begin drying out quickly, lose odor, and also become easy to dispose of. When you combine urine and feces in one tank, it becomes much more difficult. You might need powerful heaters.
  6. What do I do with the solid waste? You need to think about this carefully, because human solid waste can pollute the water and make people sick. Store the waste in a compost bin outside (I like the rotating bins). Choose a bin that is sealed, and cannot leach any liquid on to the ground (but is not airtight). Ideally you will have 2 bins. Once the first bin is full (and that can take a year or more depending on the number of users), start using the second bin. When the second bin is full, the contents of the first bin can be placed on non edible plants.
  7. How will I vent it? Vent it through the wall or roof. Most of what you need should be supplied with the toilet.
  8. How will I get rid of the urine? Urine can go into a gray water system (with the shower or sink water), or it can be drained into a rock pit.
  9. How often will I empty it? The smaller composting toilets like The Nature’s Head for 2 people need to be emptied every 3-4 weeks with full time use. The larger toilets like the Separett will be emptied about every 3-4 weeks with 4 people using full time. This varies with the amount of toilet paper that is used.
  10. Is there excellent service and support? Customer service and support is critical when buying a composting toilet. Make sure you can reach the appropriate people directly and easily. You will have questions. It’s best to buy from someone specializing in composting toilets, rather than a hardware store, or someone selling all kinds of products. You need expertise here. It’s critical to get the right toilet, and to install it properly. A person that also sells solar panels and tiny home gear may not have the requisite knowledge.

If you have other questions on composting toilets, please let me know.

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34 thoughts on “Top 10 things to know before buying a composting toilet

    • richardbrunt Post author

      This is an excellent question. Possibly, yes. If the building is fairly tightly sealed (as all newer construction is) it could happen. Especially in a smaller place. I’ve even seen kitchen range fans over power the toilet fan. The result is odor coming in to the home. The soon to be available Thinktank Waterless Toilet avoids this, because it is air tight, and draws air from outside, rather than from the bathroom (like existing toilets). If you have a toilet that draws air from the bathroom, you need to crack a bathroom window when multiple fans are operating.

  • Donna

    We are considering a composting toilet on our boat, which is in Canada, and we live in the States. The recent COVID shut down has made us painfully aware that getting to our boat when we plan (under normal circumstances, one week a month) may not always be possible. My question is, if we leave the boat for three weeks, (or 17 months, like what just happened), what would happen if there was solid waste left in the container? Would we need the fan to be running constantly while we are away from the boat? We’ve read great reviews on the Natures Head toilet, would that be the best for our needs? Also, obviously when we are away from the boat for a period of time, we would not be able to stir the contents.

  • Paul M Brenner

    The Natures Head CT with Spider handle says it requires some electricity. If I was putting this into an outhouse, would solar panel be enough during the day, and what about night time with no sun.

    • richardbrunt Post author

      In an outhouse you might try not powering it. Hook up the vent, and see if there is enough natural ventilation. There might be occasional odor this way, it’s hard to say. If you want to power it, then a solar panel will charge a 12 volt deep cycle battery. Then the battery will power the fan. That way it runs 24/7.

    • Karen Hatten

      I’m down to the nitty gritty. A composting toilet and the incinolet are the options . I’ve really been leaning towards the incinolet.. but… I really like the simpleness and back to earth end result.. Yes I’m a lil hippie.. I’m really living on a
      Old bluebird bus.. down by the bayou. Lol
      What would you say to persuade me to your side.All ears. Mostly on my on learning as things finally get done right. Or as close as I could. And behind in the cash department. Major perchase for me. Thank you… Karen Hatten

      • richardbrunt Post author

        I want you to choose the right toilet for your situation and preferences. Personally, I am not a fan of incinerating toilets because 1) they use a lot of power, 2) they are more complex, 3) if they break you’ll need a repair person, possibly an electrician ($$$), 4) the burners fail and they are very expensive parts, 5) I don’t see using a large amount of energy to burn waste as an ecologically minded approach. 6) care and knowledge is required for their safe use. This should not be taken lightly. There is basically fire down there.

        One of my suppliers (Separett) has incinerating toilets available, but I don’t list them for the above reasons.

        However, you may have valid reasons for choosing an incinerating toilet and that is fair. I think many people are happy with them. Above all, choose the right toilet for you.

  • Joseph Balachowski


    I am part of a team designing a children’s home near Gonaives, Haiti, for 32 children and approximately 8 adults. We want to incorporate composting toilets into our design package, so that the compost will feed a garden plot near the buildings.

    We don’t want to reinvent the wheel, but take a proven design that we can incorporate into our planning. Do you have drawings or diagrams showing how your system operates, plus any required temperatures, venting, chemical or other additives, and processes for moving solid and liquid waste products from the toilets, through composting to the garden?

    We would like to incorporate this information into our drawings and specifications, and of course credit SOIL as the source.

    Thank you very much,

    Joseph Balachowski
    Seattle, WA

  • Tanua Bessem

    We are in the process of opening a small campground with 20 tent sites and 5 small cabins. We are wanting to do a shower house with composting toilets. Will this work as well with much use? Can we build a larger holding container with the toilets listed on this site? I have read a lot of your info and think the Separett is the one we would use.

  • Bill Gladish

    We have an airtight house (and trailer) and I’m wondering if there is a way to feed an external air supply, so the house is not made negative pressure and the fan will be able to ‘breathe’ properly, to the fanned cavity inside the toilet?

  • Kirsten

    I’m interested in the Natures Head for my van build. How would I drain the urine straight through to the grey water tank INSTEAD of a separate bottle that needs to be emptied by hand?

    • richardbrunt Post author

      It is a fairly easy DIY modification. You drill a hole near the bottom of the urine bottle, and the urine bottle holder. Insert a bulkhead fitting in the bottle, and attach a hose. The bottle holder should be detached from the toilet, and screwed independently to the floor. This is so you don’t have to disassemble the urine drain to empty the toilet. I have pictures. If you bought a NH from me and want more advice on this, give me a call.

    • Angey Hohl

      I had the same question but also confused as I am just starting my search on composting toilets. I am just in the beginning steps of building a tiny home for me & my daughters (ironic but one of my daughters is named Kirsten). Do you have to divert the urine off if you use the sawdust? Any help is much appreciated. Thank you

  • Joan

    Hi- we are considering the natures head toilet. We are building a barn with a loft that will have some basic living quarters as a weekend getaway . We are thinking we would build a small bathroom in the lower level of the garage. It will mostly be used on weekends in the summer & fall & occasionally in the winter. With just 2 of us most of the time. I’ve watched the you tube videos & read the directions. It looks pretty straight forward. My husband is a little worried about the venting system. He doesn’t want to cut a hole in the steel building . Wondering if we could rig it to vent it out of a small section of the window that we would insulate / engineer . Or does the venting system need to really go all the way up to the roofline. I am assuming if u don’t go to the roof line anyone walking past a low vent would smell the poo fumes- am I correct? And I assume the fan runs constantly ? We will have electricity In the barn , but that fan runs all the time even when we are not there, am I correct? If the fan doesn’t run you will have poo fumes in the barn , am I correct? Thanks – sorry if these are silly questions, just doing my homework before we purchase & make sure we choose the right one for us.

    • richardbrunt Post author

      You don’t usually have to go up to the roof line for venting. Out the wall is actually better (shorter). There is a small amount of odor that comes out of the vent, but not much. I’d definitely try your idea with the window. I know a guy that put a tight fitting piece of plywood in a window opening, sealed it well, and vented through that. It worked fine.
      If you do notice odor, you can put an elbow on the vent and run it a few feet up, on the outside of the building.
      The fan runs 24/7, but with a vent there will still be air moving through the toilet. There is a good chance you will smell nothing if the fan is off for awhile.

  • Kim Galatolo

    I am purchasing a tiny home with a Separett toilet installed last year. I was told they use liner bags and coconut coir with this system, yet nothing on your blog refers to that. Is that overkill, or an option or?