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Thinktank composting toilets for tiny home

There are many reasons to consider a composting toilet or waterless toilet for your tiny home. Sewer hook ups can be problematic. Holding tanks have to be dumped or pumped. Incinerating toilets are expensive, use a lot of energy, and the exhaust can smell awful.

A composting toilet is therefore an excellent solution in a tiny home.

tiny house composting toilet

Ventilation

There is not a lot of air inside a tiny home! You must be very conscious of any fan, appliance or toilet that exhausts air, especially if it is cold or hot outside and all windows are closed. I have seen many situations where a powerful bathroom fan or range hood fan over powered the small fan in a  composting toilet. The result was stinky air was pulled IN to the home from the toilet! Ugh.

There are a couple of solutions. The simplest (and in our view the best) option is to install a Thinktank Waterless Toilet, which is an ideal composting toilet for tiny homes. These airtight toilets draw ventilation air from outside the tiny home, circulate it inside the toilet, and exhaust that same air outside. It is a closed system, and you won’t be depleting the air in your tiny home. Plus, you will save on energy costs, as you will not be blowing expensively heated or cooled air outside, as you are with we think all other waterless and composting toilets on the market today.

If you already have a composting toilet for a tiny home, you’ll need to make sure the fan in the toilet is not over powered when you turn on another fan elsewhere in your tiny home. You can crack a window in the bathroom, and shut the door. Weatherstripping under the bathroom door helps a lot.

There are commercially available systems for “make up air”. These may be a bit expensive, and are possibly overkill for a tiny home.

Vent Location

It is critically important to properly locate the vent for your tiny house composting toilet. There is not a lot of odor coming out of the vent pipe – but there is some. The end of the vent pipe should not be within 8 feet of any area with foot traffic, a door, or an opening window. Sometimes you can just go straight out the wall and that location is fine. If not, you need to go through the wall, put a 90 degree elbow on the pipe, and run it up to the roof or above. There are other options, including going through the floor. But remember that air does not like to travel through a pipe, and the pipe must be as short and straight as possible. Consult with the person who sold you the toilet, or an HVAC specialist if in doubt.

Urine Drains for Tiny Home Composting Toilets

The pee from you tiny home composting toilet must be disposed of. If you are semi-permanently located, you may wish to run the urine drain line into a French drain or gray water system. If you have to move around, you’ll need a tank situated below the height of the toilet drain. On the Thinktank this is 7 inches high, at the back. You can buy a plastic tank, or even use a plastic gas can. Remember you will have to either lift out this tank and dump it, or connect a simple pump.

Urine drain (black pipe) exhaust vent and air intake on a tiny house composting toilet

The smaller, self contained composting toilets like the Airhead and Nature’s Head have urine bottles which are removed and dumped elsewhere. While initially easier to install, this is less convenient overall, because emptying the bottle gets tiresome. Two people will empty the bottle every 2 days or so.

Power for Tiny Home Composting Toilets

Proper, professionally designed composting toilets for tiny homes have fans. Don’t believe anyone that tells you otherwise. Vast experience has proven this to us. There is stinky, moist air in your toilet. It has to get outside. There are those that say you can bury the waste under sawdust. But this will drastically reduce the capacity of your tiny house composting toilet (and you do not want to empty more often that necessary!) Also, this requires a supply of sawdust in your home which takes up space, is messy, and may contain insects. Then, you hope it doesn’t stink. No. Get a toilet with a fan.

Composting toilets for tiny homes generally use very little power. Only a small fan is required. This usually only uses 2 or 3 watts of electricity. If you have a power hook up, just plug it in to a wall outlet. If you are off grid, power can be supplied by a 12 volt deep cycle battery. (Not a car battery. These are sometimes called marine or RV batteries).  The battery can be easily charged with a small solar panel.

Summary

Composting toilets for tiny homes can be an ideal solution for the tiny home owner or builder looking for a simple, cost effective solution. If you plan carefully and pay attention to the details, you should have an odor free and problem free system for managing human waste.

How to Compost Human Waste

Composted Human Waste is excellent fertilizer for non-edible plants.

Disclaimer: These are my suggestions only, based on the comprehensive Composting Toilet Guidelines published by the Government of British Columbia in Canada, and recommendations from the World Health Organization. I make no guarantees about the accuracy of this information, and whether or not it applies to your specific situation. If in doubt you should check with your local authorities.

This is an article on how to safely and easily compost human waste. It’s not difficult, but you MUST do it right, or people could get sick. The main issue is the solid waste – feces. It’s easy to deal with urine. More on urine below.

Solid human waste (feces) can be safely composted by carefully following a few simple guidelines.

First, it is much easier to compost human waste waste from a urine diverting composting toilet. The material removed from a urine diverting toilet should be just slightly damp – perfect for composting. With a non-urine diverting toilet, the contents will be too wet for efficient composting, and the combination of urine and feces creates an anaerobic environment that allows very stinky bacteria to flourish (think outhouse or portable toilet at large public event. Ugh!). A urine diverting toilet is key to the successful composting of human waste, in my opinion.

Composted Human Waste

When the human waste is removed from the toilet, you should place it in a dedicated composter. The type of container is very, very important! It must not leach out the bottom or sides, as this might contaminate groundwater. It must be protected from rain and snow – it cannot get wet. And it must have lots of ventilation. The easiest way to meet these requirements is a rotating compost drum or barrel that sits off the ground. You can build one if you are handy, and there are many sites on the web showing how to do that. You can also buy one fairly inexpensively. In my area hardware stores carry them starting at around $100.

Some inexpensive compost tumblers have opening hatches that are a bit too small to easily accommodate a bag of human waste (which is roughly 7 gallons or 23 liters). 

Redmon Compost Tumbler

You must add other material to the compost bin, such as leaves, grass, table scraps etc. It is a good idea to learn a bit about composting basics online. You need about a mix of “greens” and “browns”. Much has been written about the “correct” ratio, and no one seems to agree. I don’t think about it too much, and add roughly 50:50 greens to browns. Human waste can be considered neutral, and not a green or a brown.

If possible you should “feed” your compost bin with something every week. This keeps things going, and speeds up the composting process. At a minimum, you should definitely monitor the contents from time to time. If it seems wet (it should be just slightly damp), add dry grass, dry leaves, or some other dry carbon rich material. If it’s too dry, you’ll need to add a bit of water, and possibly more nitrogen rich material like green plants. It’s actually pretty simple and easy. Keeping the contents just slightly damp will ensure rapid and complete composting.

Compost Tumbler with large opening hatch

Additional Tips to Successfully Compost Human Waste

You need two compost bins to compost human waste. Use one at a time. When the first bin is full, start using the second bin. When the second bin is full, the first one should be ready for the plants.

There are bins with two chambers. This is intriguing, but I have not tested them. I don’t know if the capacity of each side would be sufficient.

Add lime to the compost bin. This will drastically reduce the time it has to sit, before being safe to bury or spread on non-edible plants. Use roughly 3% lime to total waste volume – i.e. if you have a full 50 gallon drum of waste, use 1.5 gallons of lime. These numbers are very approximate. With lime added, the bin needs to sit undisturbed, without adding new material, for 120 days according to the BC Composting Toilets Guidelines. This should kill all pathogens. Without the lime, the time frame is much more uncertain, and varies from 6 months to 2 years, according to various sources.

You must never put composted human waste on edible plants, because of the small chance that dangerous bacteria is still present. Always use human waste compost on non-edible plants only, or bury it.

Pee is Easy!

It is extremely easy to deal with urine from a urine diverting toilet. You can just use it as fertilizer! Some people dilute it, others do not find dilution necessary.

You can download a wonderful guide to using urine as fertilizer from the Rich Earth Institute here. They have worked with numerous universities, public health regulators, the WHO and even the EPA to establish principles for using urine from a urine diverting toilet as fertilizer. The take away message from this guide is that, at the household level, urine is not a health risk, and can be used directly on plants without treatment. Sadly, many (most?) local governments are unaware of the facts around urine, and think it is somehow dangerous. Not true. Send them the guidelines.

If you follow these simple steps, you will have a complete, safe, odor free and low cost waste treatment facility on your property. Unlike conventional sewage or septic systems, you will completing the circle of nutrients, returning much of what you consumed back to the earth. You won’t be creating toxic sludge to be burned in a high temperature furnace, or treated in a typical sewage treatment plant using vast amounts of energy and producing considerable CO2.

Compostable Toilet Bags

Glad Tall Compostable Bags

Separett bags

Separett Bags

I get many questions about what bags to use in a Separett toilet. These need to be compostable bags that will readily break down in a compost bin. The actual Separett bags are excellent, but they are a bit expensive. There are other compostable bags, commonly available at hardware stores, grocery stores, and online – for far less money. These bags may be thinner than the actual Separett bags, so you might need to double bag the bucket. You need the bag to be 7 gallons (26 liters)  or larger.

NOTE: It is important to choose a true compostable bag. These are usually made from corn starch. There may be “bio-degradable” bags available that do not compost as well.  A true compostable bag breaks down very easily, (although there may be some harmless traces of it in your compost.) It should say on the box if it is a compostable bag or bio-degradable bag.

Recently a company called Unni World has started making compostable bags which are designed for toilets. I’ve not tried them yet but they look pretty good. They are the correct size for the Separett toilet.

Unni World Compostable Toilet Bags

Unni World makes bags designed specifically for composting toilets

Glad Tall Compostable bags are commonly available – and inexpensive. They are a good alternative to Separett bags. You may also wish to try other brands.

Bin with Separett bag

You don’t want your compostable bag breaking open while it is still in the toilet. Therefore, you want to double bag the bucket, or use the thicker Separett compostable bags.

If the toilet is emptied infrequently, the bag could begin to break down inside the toilet. This is not a big problem. Just dump the entire contents of the bag into your outside composter, rinse out the bucket with water (if it is dirty), put a new compostable bag in the bucket, and you are good to go.

You should have two composters to compost your waste. These should not be open to the ground underneath, as they could leach. I like the rotating drum composters. Use one at a time. After the first drum fills up, you can start using the second drum.

compost tumbler ideal for composting humanure

When the second drum is full, you can put the contents of the first drum on non-edible plants. Adding lime greatly speeds up the process. With lime added, your compost should be ready for the plants after 120 days (above freezing). I do not recommend a specific brand of compost drum, but there is an excellent review of the best models here.

Read Separett FAQs here.

You can read more and watch videos on the Separett toilet here

How Our $33,000 Tiny House Changed Our Lives – by Gabriella Morrison, author of Tiny House – Designing, Building, Living

The tiny house movement has taken the nation by storm and is rapidly spreading to other countries around the globe as well. The genesis of tiny houses, as most of us picture them, came from the creative vision of a man named Jay Shafer. In the late 1990s Jay grew tired of spending winters in his Airstream which was not insulated and adapted for a midwest climate. Sparked by ideas he’d seen in some home-built RV books, he took it upon himself to design and build his own diminutive home on a trailer base. It suited his needs and saved him a ton of money over conventional housing.

There’s no way that Jay, or anyone for that matter, could have predicted how much his tiny house was going to alter the very tapestry of housing in the US. Tiny houses are now bona fide, offering solutions to those in financial need, veterans, college students, environmentalists, minimalists, and more. Codes and zoning are changing at rapid speed to accommodate the swelling of interest. Outside industries are rushing to create solutions specific for tiny houses (insurance, lending, technology, construction materials, appliances, etc.). What was once a sparse desert is now a tropical and lush landscape teeming with life and opportunity.

tiny house kitchen

People from all walks of life become enchanted with tiny houses. Truly, with our website www.TinyHouseBuild.com as a DIY resource charged with empowering novices building their own tiny house lifestyle, we hear from people as young as 14 to as golden as 80. From homeless people who are excited to finally have the opportunity for safe shelter, to retirees who would rather save resources and live in something that isn’t wasteful. From soon to be college students who don’t want to follow in their previous generations’ footsteps towards debt, to young families who above everything else value time spent together and a lifestyle that promotes that possibility.

For my husband, Andrew, and I personally, we were driven to the tiny house movement after discovering that in finally achieving the infamous “American Dream” in 2009, we had paid the ultimate price: time away from our two kids, an increase in stress, and a radical deterioration of our happiness. Our new beautiful house had dismantled years of close connection as a family and a lifestyle focused on joy, health, and experiences rather than material possessions. Six months after move-in, we discovered the tiny house movement and within six months after that, we had gotten rid of the house, 90% of our worldly belongings, bought a pop up tent trailer, and moved to the tranquil beaches of Baja, Mexico to “reset”.

tiny house hallway

In our 150 sq ft pop up tent trailer, we realized that while living with the least, we were experiencing the most. Our inter-personal relationships improved to their best selves ever, and the inner tranquility we felt from a slow lifestyle was so intoxicating that we struggled to come back up to the States to rejoin our lives up here. In that moment, we committed to creating a lifestyle that would best give us the possibility of success and inner calm: we decided to build a tiny house.

About three years after living in Baja, we found a very inexpensive piece of acreage in beautiful southern Oregon, designed and built our tiny house, and lovingly named it “hOMe”. The cost to build it was $33,000 which included all of the appliances and furnishings. Nearly half the cost of just the DOWN PAYMENT of the average house in the US. Assuming we never move out of here, we will never, ever have another housing payment again. The amount of stress we’ve been able to alleviate through this truth has been significant.

Our family of four lives on five mountaineous acres in an off-grid set up. We generate our electricity from the sun 9-10 months out of the year and rely on a gas powered generator on sunless winter days. Our Separett toilet is a large part of what makes our off-grid lifestyle so successful. One never knows just how invaluable a well functioning toilet is until they don’t have one. We had tried two other composting toilets when we first moved into hOMe and they had been disasters. We have been using our Separett for over three years now and still love it. We put our waste in a three stage composting bin away from our house and allow decomposition to transform it all. No odors, easy maintenance, no crank levers, easy urine management, and a nice, sleek look.

Tiny House Toilet

We have been living here for over 3.5 years and we continue to love it. Both Andrew and I work from home full time and we’ve found this space to be extremely conducive to a focused work environment. We spend a lot of time cooking and so our full sized kitchen with full appliances accommodates our active family’s needs. Our kids are 20 and 17 years old and use hOMe as their main base. Being a close family, they are often in here hanging out, watching a movie, cooking in the kitchen, and using the bathroom facilities. It’s truly amazing how well we are all able to flow through our tiny house without bumping into each other. For sleeping, both of our kids have their own small cabins right next to our place. They have no plumbing but do have power. This has been a wonderful arrangement for our family.

Tiny house living isn’t for everyone but our observation is that it’s a perfect fit for those that value close relationships with those they live with, those that are motivated to live a life that is economical and light on the planet, and those that are willing to deal with discomfort during a transition period. Most of us will go through a significant and often uncomfortable transition when first making the move to tiny. It’s not easy at first (it wasn’t for us) because most of us aren’t used to living in such close proximity to others. I can tell you though that after our own experience, and also from hearing from hundreds that have made the move to tiny, that the initial stage is very short and on the other side is a lifestyle that is more rewarding, peaceful, and joyful than most of us could even imagine.

Note: Tiny House Build now offers plans! This is probably the best place on the web for tiny house plans. Visit them at tinyhouseplans.com

Top 10 things to know before buying a 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.

Urine diverting toilets are a significant improvement over older composting toilet designs, that combined urine and solids together in one tank. Urine diverting toilets eliminate most of the liquids in the composting chamber, substantially reducing odor, and making the break down of solids much easier.

Although most composting toilets work fine when properly installed and very carefully operated, I do frequently hear complaints from people who say their toilets “are not working” or that they simply smell bad.

The main problem is usually too much liquid from urine. If the contents are too wet, you will not get compost. You will get a sodden, stinking mass of sewage. Odor problems can certainly occur. In theory, the urine should be evaporated by the built in heater and/or fan. But in practice, the volume of liquid may simply be too great for this to be accomplished. Emptying a toilet full of un-composted material is hard to even think about.

To try and solve this problem, many non-urine diverting toilets have overflow drains to handle excess liquid.  These drains MUST be clear and working properly. The overflow drain must be led somewhere below the toilet itself so gravity can cause it to flow away. That may be difficult, especially if you are already at ground level or don’t want to cut holes in your floor. Also, you need a sump, container or pit where this excess urine can be stored. If you have a properly working overflow drain, you should have no problems. The overflow will be urine mixed with feces, so it cannot go into the gray water system. It cannot be drained into a pit, and it cannot be used as fertilizer. In other words, it’s a problem.

A better mousetrap?

A superior solution in many ways is a urine diverting composting toilet (also called a urine separating toilet). These have only recently become more widely known. You use the toilet normally, but most of the urine is diverted automatically into a separate container. This means the solid contents remain only slightly moist – perfect for composting. Separating the urine solves the excess liquid problem common to most conventional composting toilets. The urine has not been contaminated with feces, so in many areas it is legal to send it into the gray water system. Typically, this will be a tube running from the urine diverting toilet to the drain below the bathroom sink. Or you can store the urine in a tank, dilute it with water, and use it as fertilizer. It can also simply be led into a small drain pit beside the dwelling.

According to the group SOIL (sustainable organic integrated livelihoods) – a non-profit that builds composting toilets in Haiti – urine diverting toilets are the way to go.  They have experimented with many different methods. From their website:

“Urine Diversion toilets have the significant advantage of reducing the amount of waste that needs to be transported therefore reducing gasoline consumption and costs. Because the excreta remains dry, the toilets are also less odorous than other toilet models and very pleasant to use.”

Other advantages

Another advantage of the urine diverting toilet is that no heater is necessary. Some composting toilets made by Envirolet, Biolet and Sun-Mar use heaters of up to 500 watts. That could be a significant cost, with our soaring energy rates. And what is the point of installing a “green” toilet if you use large amounts of electricity to run it? The heaters may eventually fail, costing more money. All manufacturers do have non-electric or 12 volt models, which use little electricity. However, you must be extremely careful to have a working overflow drain in those non-electric toilets.

Urine diverting toilets need only a small, inexpensive, easy-to-replace fan that uses very little electricity. Or they can be hooked up to a solar vent and you can forget about the fan and power use entirely.

Solid human waste is approximately 85% water by volume. This means that a urine diverting toilet will have enormous capacity for its size. The solid material dries out and shrinks dramatically (just like a compost pile in you backyard).

And finally…urine diverting toilets do not have any problems whatsoever with odor – unlike some older models of composting toilets.

Still not perfect

However, even with a urine diverting toilet you still need a way to dispose of the urine. Fortunately, this is fairly easy. Urine is almost sterile (advanced lab techniques sometimes identify a tiny amount of bacteria) and does not pose a health risk.

The easiest solution is to run the urine drain into the gray water system. If you don’t want to go that route, you can build a simple “French drain” to solve the problem. This is a small pit, about 2′ wide and 2′ deep, filled with small rocks. You cover the rocks with landscape fabric and place soil and grass seed on the top.

Run a tube from the toilet, through the wall or floor and directly into the French drain adjacent to the building. This way you will never have to think about the urine again, as it is getting disposed of constantly.

You can also store the urine in a plastic tank, and dilute it with water 10:1. It is then exceptionally good fertilizer.

Many people install the smaller urine separating composting toilets on boats and in RVs. In this case, the urine can be dumped in any conventional toilet or outhouse as needed.

Capacity

Some urine diverting toilets, such as the Nature’s Head, are smaller, self contained units suitable for 2 people full time or weekend use for up to 4 people. The larger Separett toilets have more capacity and are suitable for a family and general household use. Either toilet will be emptied about once every 4-5 weeks with full time use. This takes between 2 and 3 minutes, and is not unpleasant. Unless you have just used the toilet, there will be little or no odor when you empty it. Urine diverting toilet seats are available for the handy do-it-yourselfer that wants to build their own urine diverting toilet system.