A surprisingly difficult decision: choosing your off-grid dunny for your inner city house

by | Dec 26, 2022 | Building/Design

Who’d have thought it? My toilet has been one of the most difficult decisions in my planning so far. There are literally hundreds of different ways off-grid enthusiasts can deal with human excreta. But many of them won’t work for me.

I don’t want it to be this hard for you. So I’ve asked Kirsten and Ashton of ecobuildlab.com for their advice, and added some of my own experiences and research to compile this list of considerations.

I hope it helps guide your choice.

1. First up, what is your overall green philosophy and where do you want your waste ultimately to go?
Are you 100% committed to living off the grid and being 100% self sufficient, even if it means using a lot of solar power and time spent dealing with the compost from a composting toilet? Or do you want to be as passive as possible with energy usage and say, burn propane when you need to (e.g., some toilets allow you to store propane for cooking). Someone did say to me though, that they didn’t like the idea of their food being cooked by farts! HA! Ashton also mentioned that some toilets can create biogas which you can cook with as well. Biogas is different from propane. The biogas cooktop is different too. If you have a propane oven and want to send biogas to it, you will need a converter.

If you’re not going 100% off-grid (maybe just off grid for energy and water) you might be happy to connect to waste-water treatment in your city? If not, you’ll need to consider either onsite septic with blackwater treatment, an incinerating toilet, or a dry/composting toilet.

Different people have different priorities and you need to be clear on this, because as Kirsten and Ashton say, there will be choices to make on which resources you use and which you reject. For me it’s really important to be disconnected from the sewerage system. If we all dealt with our own poo on our own property we wouldn’t have to build enormously expensive treatment systems and we wouldn’t be pumping poo out into the ocean either!

There will be sacrifices whichever way you go – everything is a trade-off.

2. Do you want it to be a dry toilet or a flush toilet?
These are the two main types of off-grid toilets: Dry toilets, and flush toilets. Your choice will depend on how you answer a whole lot of other questions, like these below. But in general, the flush toilet requires water (which could be recycled greywater) and somewhere for that water to go like a septic tank with a blackwater treatment cell or simply plumbing to municipal waste treatment). Dry toilets require you to either compost the waste or light it on fire (incinerating toilets).

Image source: ecobuildlab.com

Image source: ecobuildlab.com

Image source: ecobuildlab.com

3. What’s your climate and water situation?
How many rainy, windy and sunny days do you get at your house, and what are the prevailing winds?

If you live in a really arid climate, and you’re subsisting on rainwater harvesting, you’ll probably want to consider a dry toilet or some type of water-recycling toilet. In Kirsten’s location, she only gets 8 inches of total annual precipitation, and her house is exclusively water harvesting. So the water from her shower and bathroom service (greywater) is used to grow food in a greywater treatment cell (which filters the water) and then goes onto flush the toilet. This system is brilliant because the planter cell is the filter! By the time the water goes completely through, it is clean enough to be pumped back into the bathroom to flush your toilet.

Image source: ecobuildlab.com

Kirsten has an additional planter cell outside her home, located between her septic tank and leach field to make use of the blackwater coming in from her kitchen sink and toilet. The grey and black water recycling system shown below is from earthshipglobal.com, but I’ll write more on these systems in a future blog.

Image source: earthshipglobal.com
If you live somewhere really rainy, then you might not need to worry about having to recycle all the grey water you use. But you might have to worry about what to do with excess water if you want to be disconnected from the grid! That’s my issue, I might have too much grey water to use and not enough potable water (but that’s a blog for another day).

4. What’s under your house?
Sounds like an odd question, but if the ground under your house is basalt for example, you can’t dig down for a planter, so you wouldn’t be able to adopt Kirsten’s solution above. You would have to go the compost toilet route or an incinerating toilet (which if everything goes to plan is the route I’m taking)

5. What are your existing council/state building codes relating to waste-water treatment?
Do you need to get approval for your waste-water solution before you build it? Are you even allowed to do a dry toilet? Are you required to have a conventional septic tank that flows into a leach field1? You’ll need quite a bit of space
There are minimum lot sizes for having a septic tank in the US, which is generally way bigger than a city lot. On my block in Newtown I definitely can’t have a composting toilet, my council won’t allow it.

If you’re committed to the cause and you have the time, you can get around regulations sometimes. Kirsten mentioned that Earthship Biotecture worked with her state government to test pathogens at the end of their treatment system. The study concluded that with woody fruit trees and bushes, there were no pathogens. 

1water leaches out from the pipes to the soil where it is filtered again and broken down by microorganisms and bacteria

6. Do you want a garden and have the room for it?
If so, a composting toilet may be a good idea. It gives you more good stuff for the garden. Kirsten and Ashton also explained how the recycled black water could be used for a garden to grow food! Here’s an example! But they get the food tested to make sure it’s all ok to eat.

Kirsten told me to check this book out: The Humanure Handbook: Shit in a Nutshell. Here’s a quote from the link:

“Not only does the book address what to do with human turds, but it is also a priceless manual for anyone involved in composting, gardening, or even basic survival skills. There is no other book like this in print!”

I haven’t checked it out yet, but so far I want to just because the author seems pretty funny!

7. If you do want a composting toilet, which kind?
Some composting models separate your solids from your liquids. Some are more of a “bucket chuck it” system (as Kirsten and Ashton label it), like a luggable loo made up of a bucket with a toilet seat. With that option, you throw in some wood shavings or similar, then throw it all in your compost pile outside (your “humanure” pile). And other options again have a grinder.

8. Do you have enough sun and solar panels for a solar toilet or an incinerating toilet?
Kirsten and Ashton told me about a solar toilet that’s like a solar oven with a reflective glass window facing south (or north in the southern hemisphere). In theory it fries the solids to an inert ash you can throw on your garden. In reality, the workings of these can get gummed up, they say.

Bear in mind that anything with an electric heating element is a huge draw on the solar system. They told me that to do an electric on-demand hot water system you’d need 80 deep cycle lead-acid batteries to be paired with 80, 250-watt solar panels.

In my case, I have so many constraints, I have to have this Cinderella toilet which is going to be really power consumptive, but there isn’t much choice. When I talked with my solar expert Roland Lawrence, he confirmed that I will have to reduce electricity consumption across everything else in my house so I can have this toilet; but I’m prepared to accept that rather than plugging into Sydney’s septic system. Maybe I’ll be going to the toilet in the dark???

9. What do you want your bathroom experience to be like?
Do you need it to feel like a conventional toilet for your household and guests? Kirsten has an off-grid Airbnb which uses grey water for flushing and it looks like a normal toilet. Plus there’s little to no daily maintenance for her, beyond small repairs over the years. If your planter’s functioning properly there’s also no odour with the grey water. The toilet in Ashton’s house looks perfectly normal too.

10. How engaged do you want to be in your waste removal?
Are you happy to meet nature halfway, or do you not want to know about the poo and wee? Different systems require different levels of commitment.

If you’re contemplating a composting toilet for example, can you commit to creating compost piles? Do you have the time and inclination to be adding more green and brown material to them, and turning them over and moving to the next pile? Then ageing them out to the point where they’re safe enough to put on your garden, and making sure your dogs aren’t hopping into raw compost?

Yes, it’s a thing.

11. How much space do you have?
Grey water planters take up a lot of space. Basically, you need a yard for the black water cell. It’s an expensive process, way more than a compost toilet, when you include excavating, putting in the rubber liners, buying the gravel and sand and all the layers you need to make it work.

But on the other hand, it’s completely code compliant, and it’s designed to be set up totally conventionally but with the additional aspect of filtration and plant growth.

Blackwater cells are not always code-compliant. Municipalities may accept them since all the required elements are there (septic tank + leech field) BUT some municipalities may not approve of them. Kirsten said they can not guarantee code compliance with the systems they have implemented.

Image Source:

BRStoner, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

12. How many people will be using the toilet?
For example, my toilet uses electricity everytime someone uses it. If 10 people were using it consistently then it’d chew up a lot of energy! In the case of a composting toilet, you’ll have to empty it faster and there may not be enough capacity for it to have composted for long enough.

13. Are you uncomfortable contributing to landfill?
If so, don’t go with the Lavio Dry Flush. As Ashton says, you’re “peeing and pooing into a space bag”, which wraps your poo into a container that gets tossed into landfill. So you have to keep buying bags and they’re not compostable.

14. What kind of budget do you have?
If your mentality is that you should be able to turn on the tap and there’s unlimited water; and you want to be able to turn on everything in your house all the time and there’s unlimited power, then it’s going to be difficult and/or expensive to achieve this.

There are pros and cons for every type of toilet, and there is a solution for every home. Even The ImPossible House!

Kirsten and Ashton are writing a book that will include lots more information on these options to help people weigh up what’s right for them. I’ll let everyone know when that book is published. They also have their first online course, Off-Grid Jumpstart and will have a podcast as well. Bloody hell guys! Busy much!?!?! Go you good things!!

Here’s a picture of their lovely mugs!

And one final point: before you decide on a toilet option, find out what’s the lived experience with the product. Talk to people who have used it, don’t trust the product claims.