How A Composting Toilet Works In A Tiny House (Explained)

Solar powered dry composting toilet, with a bird nest in the column of the solar power pole. The power is used to drive the exhaust fan.

Living in a tiny house requires changing your lifestyle in a few significant ways, and that includes how you go about your business.

While you can install a regular flush toilet in a tiny house, those take up a lot of space, and hooking up to your local sewage system can cost tens of thousands of dollars. (Link). For convenience, most tiny house residents use other options such as a composting toilet.

How does a composting toilet work?

Most composting toilets have a composting mix in the tank, which breaks down waste immediately. Advanced models have separate tanks for liquid and solid waste. Once the tank is full, you empty it, clean it, and replace it. Other than that, a composting toilet works just like a regular toilet.

Composting toilets are surprisingly similar to regular toilets once you get used to them. However, they still require some adjustments.

Here is how a composting toilet would work if you installed one in your tiny house.

How Do Composting Toilets Work?

Composting toilets work by immediately breaking down waste in your tank. Instead of water or electricity flushing away the waste, you manually remove it when the tank is full. By the time the tank is full, the composting mix will break down your waste into renewable, compostable material.

The most modern composting toilets and the type that most tiny house owners swear by are urine-diverting composting toilets. These composting toilets have two separate tanks for liquid and solid waste.(Link)

Using gravity and strategically placed flaps, your waste gets separated. This means you can go longer without emptying out the solid waste tank, and it will hopefully smell nicer. (Link)

Setting up a composting toilet is relatively easy. All you need to do is hook up the toilet to your bathroom and fill the tank with composting material.

The most common composting materials are wood shavings, sawdust, and coco pith. Mix the composting material with enzymes that you can get at the store, which will speed up the composting process.

Emptying the tank is done mechanically, which means that you will have to get your hands dirty(wear gloves!).

In urine-diverting toilets, you need to empty the liquids tank every two to three days. The solid waste tank can last longer, usually three months.

You can either bury the solid waste contents in the ground as compost or put them in a trash bag and dispose of them like you would dirty diapers and dog poo.

Then, clean the tank, refill it with soaked, prepared composting material, and replace it.

What Types Of Toilets For Tiny Houses Are There?

We mentioned urine-diverting toilets above, but you have a few more options when it comes to composting toilets. Here are the different types in more detail:

Urine-Diverting Composting Toilets

These are the most popular among tiny house owners.

These toilets have two separate openings leading to two separate tanks for liquid and solid waste. They often have less odor, and you will need to clean the tank less often. Many of these toilets come with exhaust fans.

Drop Composting Toilets

Drop composting toilets are the more traditional type of composting toilet. All waste goes into one tank which is full of composting material. While these are simpler to install and maintain, they often smell worse because liquid and solid waste mixing and mingling causes odors.

DIY Drop Composting Toilets

If you’re feeling creative or operating on a low budget, then you can make your own composting toilet.

All you need is a large bucket into which you can put composting material. Then, put a toilet seat over the bucket or build a commode out of wood if you’re feeling fancy.

DIY composting toilets are great when you’re just starting out or you’re on a very low budget, but they tend to smell the worst and feel rudimentary after a while.

Macerating Toilets

Macerating toilets are like a fancier version of compost toilets.

Instead of relying on enzymes and composting material to break down waste, the mechanics of the toilet break down waste into a slurry and then divert it into a septic tank. (Link)

Macerating toilets require connection to a power source and a septic tank, so they are not always the best option for tiny houses.

Dry Flush Toilets

If you really want to have a flushing toilet in your tiny house but don’t want to have to hook up to a septic line, then dry flush toilets are your best alternative.(Link)

The toilet bowl has a foil lining that wraps your waste when you flush. However, this type of toilet uses electricity and can be expensive.

Incinerating Toilets

The last type of toilet commonly found in tiny houses is an incinerating toilet. (Link)

Incinerating toilets burn waste into ash which you can easily dispose of. However, they are very expensive and use a lot of electricity during the burning process, which is not ideal if you started living in a tiny house for sustainability reasons.

Do Composting Toilets Smell Bad?

The most common worry people have about switching to a composting toilet is the odor.

They expect that because waste is sitting around in a tank, it will stink up the whole house—and in a tiny house, you don’t exactly have somewhere to go to escape from bad smells.

Some toilet odor from composting toilets is normal, but then again, regular flush toilets don’t always smell that nice either. The most common odor you smell will be compost material, not poop or pee.

If you close your bathroom door and clean your toilet regularly, you won’t even notice the smell. The odors will also depend on the type of composting toilet you use.

Old-fashioned drop composting toilets and DIY bucket toilets are the reason why there’s the stereotype that composting toilets smell bad.

That’s because the key to managing the smell of solid waste is to keep it dry. When liquid and solid wastes mix, the moisture activates the enzymes and makes them smell worse.

Urine-separating toilets smell much better because they separate liquid and solid wastes.

If you really want to manage toilet odors, invest in an exhaust fan. Exhaust fans connect the toilet to the outside by going through your wall. The fan sucks out air from the toilet and sends it outside instead of letting it bubble up into your bathroom.

Exhaust fans do require electricity to work and have to stay on constantly, so you will have to add a bit more to your power budget.

However, you can also find solar-powered exhaust fans if you are concerned about sustainability.

How Do You Use A Composting Toilet?

Using a composting toilet, especially if you are using a urine-diverting toilet requires some getting used to.

It’s not as easy as sitting (or standing), doing your business, flushing, then forgetting all about your waste as it merrily flows away to the municipal waste treatment plant.

It may seem strange to think so much about your waste and adjust how you go to the toilet, but it will ease the cleaning process when you need to empty out the tanks.

When you have guests over, explain how to use the toilet when they first arrive or print out discreet instructions that you could pin up in your bathroom.

Peeing

Peeing with a composting toilet is pretty much the same as with any toilet. The only difference is that you have to aim for the liquid tank, the hole towards the front part of the toilet.

Some toilets don’t divert urine automatically but rely on the pressure from sitting down to open the flaps to the tank. For those toilets, everyone has to pee sitting down.

Automatic urine-diverting toilets don’t rely on pressure sensors to open the tanks so those who want to can pee standing up—just emphasize the importance of aiming because composting toilets don’t have seats that lift up!

Pooping

Pooping in a composting toilet is a bit more complicated because dealing with solid waste requires a bit more effort.

Some people recommend placing a coffee filter in the toilet bowl as a liner before pooping. Since you don’t have a flush mechanism, any skid marks on the bowl will stay there, causing odors, unless you get up close and personal with a sponge to clean them.

Prevent that hassle with a biodegradable liner that will go into the solid waste tank.

Try to aim for the back of the tank as you do your business. Some toilets automatically open the flap to the solid waste tank, but others require you to manually toggle once you’re done with your business.

The manual toilets will also require turning a crank to move the compost around.

Whenever you’re doing business in a compost toilet, try not to use a lot of toilet paper as too much paper will clog the mechanisms and take up unnecessary space in your solid waste tank.

Menstruation

Not much changes when using a compost toilet while menstruating compared to using a regular toilet.

If you use the toilet and notice blood on the bowl, use a spray bottle to wash it off (some toilets already require spray bottles of water and cleaning solution to flush anyway, so this doesn’t require additional equipment).

If you use a menstrual cup(Link), empty it in the bath, sink, or directly outside. Don’t empty it in the liquid waste container of your toilet because usually, you clean out the liquid waste tank by just dumping it outside.

You can do that with urine without damaging the environment, but blood will not be as pleasant.

You shouldn’t flush disposable pads and tampons down any toilet, but it’s even more important not to do that in a composting toilet as you could clog up the mechanism. (Link)

How Do You Clean A Composting Toilet?

If you want to have a fresh-smelling home even with a composting toilet, it’s very important to clean it regularly.

Disposing Of Waste

The first step when cleaning is usually to dispose of waste.

You need to empty the liquid waste tank every few days and the solid waste tank every few months (that’s with two people using the toilet full-time. A larger family will need to empty the tanks more often).

Remove the liquid waste container by unlatching it from the rest of your unit (the liquid waste container is located at the front of your toilet).

Dilute the liquid waste with water at a ratio of 1:10 then pour it out somewhere safe—urine is actually a great fertilizer. (Link)

Dump solid material into a compost pile or a garbage bag and then into a dumpster.

If the solid waste has too much liquid content, for example, if someone in your household had diarrhea, then add some more compost peat to the tank and mix it in before dumping the waste out.

Before setting up your toilet, check local regulations for dumping waste and find a place on the property where you can safely get rid of the contents of your toilet, whether that’s a compost pile or a place where you can dig a hole and bury your waste.

Cleaning The Bowl

Since there is no flushing mechanism, your toilet bowl is in danger of getting dirty.

Prevent remnants of solid waste by lining the bowl with a biodegradable coffee liner before you go. If you notice a mess on the bowl even with the liner, spray it down with a few spritzes. Keep a spray bottle by your toilet with a diluted vinegar solution for this purpose. The vinegar should dissolve any mess and combat odor.

Cleaning The Tanks

When you need to empty out your tanks, that’s also when you should be cleaning them.

Start by rinsing the buckets with warm water and cleaning them with disinfectant. Don’t use a strong disinfectant such as bleach because that kills off the enzymes that you need to compost your toilet and, ironically, will lead to more smell.

When the liquid and solid waste tanks are removed, that’s also a good opportunity to clean the rest of the toilet.

Using water, a brush, and a good cleaning solution, clean the toilet seat and under the flap. Once a week, you can disinfect the seat as you would with a regular toilet and pour hot water down the urine container to get rid of any build-up.

As with any toilet, you should have designated cleaning tools on hand so you’re ready to handle a mess.

A compost toilet may require some additional equipment.

Besides a brush, bucket, and cleaning solutions, you should have a hose and a shovel if you plan on burying your waste.

Investing in gloves and grubby clothes or a protective apron so you don’t contaminate your clothing is also a good idea.

Frequently Asked Questions

Here are some of the most common questions people ask when they’re looking into a composting toilet.

Q: How Much Electricity Does A Composting Toilet Use?

The answer depends on the type of composting toilet that you have. (Link)

A regular drop composting toilet or a DIY bucket composting toilet doesn’t use any electricity at all. Other units that have electrical features such as exhaust fans use 80-150 watts. 

Check the specifications for your unit before you buy it.

Q: Can You Use A Composting Toilet In Winter?

Yes, you can use a composting toilet in the winter, but it will be harder. (Link)

In cold weather, compost goes dormant, and your waste will no longer break down, it will just sit there. You can prevent this by insulating your composter and replacing compost more frequently to keep things moving.

You can also switch out your regular composting mix by adding a bulking agent to protect the aerobic bacteria.

The biggest consideration when using a composting toilet in the winter is that if you usually bury your solid waste, digging a hole will be harder.

The Final Word On Composting Toilets In Tiny Houses

Composting toilets are, in some ways, the best of both worlds of living in a tiny house.

You get the comfort of using a regular toilet without spending money on sewage hookups because these toilets work by composting waste directly in the tank.

Once the tank fills up, you can dump it outside, in a compost pit, or bag your waste like diapers and throw it in a dumpster.

It’s worth investing in a urine-diverting composting toilet instead of a regular drop composting toilet because separating liquid and solid waste makes for easier maintenance and reduces odors.

In general, compost toilets don’t smell as bad as people expect, especially if they’re cleaned regularly and hooked up to an exhaust fan.

You should be prepared for a bit more maintenance than you need with a regular flush toilet.

You need to take extra care to keep the bowl clean and empty the tanks manually.

As long as you’re not afraid to get your hands dirty, a compost toilet is a comfortable, affordable, and sustainable solution for tiny house living.

Sources: 

www.greywateraction.org / www.letsgogreen.com / www.tinyhouseblog.com / www.momgoescamping.com / www.wikipedia.org / www.fredstinyhouses.com.au / www.angi.com