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What is a Compost Toilet?

Scientific explanation: A type of toilet that treats human excreta by facilitating composting through the biological decomposition of organic matter.
In other words: An eco-friendly and functional toilet that turns human waste into usable, hygienic fertilizer.

Compost toilets typically use no water for flushing and you may also see them called “dry toilets”, “biological toilets” or “waterless toilets”.

Let’s get the obvious question out of the way now. 

Believe it or not, composting toilets are odorless. Air is continuously drawn in to the unit and up the vent stack, creating a partial vacuum in the unit. In addition, the composting drum fosters a good aerobic compost which produces no odors.

Composting toilet: this type of toilet composts with something like sawdust. They are often used in areas with easy access to wood shavings and leaf duff. The finished product is a moist humus similar to garden compost.

The breaking down of waste involves a process called aerobic bacteria which breaks down material (find a reference site for this explanation).

Dry toilet: dry toilets are used in more arid, dry climates where lime and ash are more accessible than sawdust. Toilet paper cannot be added to this toilet type. The finished product can be used as a soil amendment and resembles instant coffee. Ash or lime mixed with dry soil are added to a dry toilet to create a dehydrating environment for the breakdown and dirt off of pathogens (source:

Yes. Many composting toilets come with a child seat. Children do quickly learn how to sit correctly.

The size and length of any vent pipes will vary depending on the composting toilet you buy. This is generally adequate for a direct through wall installation. For longer vent runs, composting toilet companies often offer adaptors.

No – not into a chimney. It may be run into an existing septic vent stack with precautions – keeping in mind that if there is an electric power outage  a shut off need to be in the line to isolate the toilet.

No. It does not smell since the urine is let out in the ground and diluted with rain if you are using a soak-away pit. The urine line must have a negative slope as it is a gravity drain. If going to a soak-away or leach field, a trap is generally not needed in the line. If a holding tank or grey water tank is used for the diverted urine, it is important to have a vent on the holding tank. and a p trap between the tank and the toilet in the same manner as a sink or shower running into the tank would have. The trap keeps any odor that may develop within the tank from returning back up to the toilet.

Problems with flies are uncommon. However, flies may enter the toilet from the bathroom if you leave it for a week or so with the fan switched off and the container with solids still in place. The fan should always be operational.

Most can. However, at sub-freezing temperatures, plastic and other materials used may become more brittle. Before you purchase a composting toilet, make sure you understand what weather conditions the composting toilet can withstand.

Yes. There are not usually any problems for the average DIY person installing a composting toilet. Closely review any installation videos and instructions provided to you from the manufacturer or re-seller.

Yes. Fans and heating elements often require power. Some units can be powered by batteries or a solar panel. Many composting toilet manufacturers have both electric and non-electric options.

Why get a Compost Toilet?

There are a few reasons why people choose to use composting toilets. Here are some of the main reasons:

  1. Composting toilets do not release contaminated polluted water into our water supplies. This makes for cleaner oceans, bays and rivers.
  2. Waterless composting toilets save water and electricity. They do not need either. That means it is an environmentally friendly toilet option. It also means you save money.
    1. Compost toilets can save 25,000 litres of water per person per year.
  3. A composting toilet breaks down human waste into usable elements like water and carbon dioxide. Gotta love recycling. What remains of the waste has reduced in volume by about 90% and is chemically, biologically and aesthetically similar to topsoil. This dry-compost material is collected via the inspection door and can be used as garden compost (source:
    1. Compost toilets produce around 30 kgs of compost per person per year.
  4. In many cases, people use composting toilets because they are on a path to living self- sufficiently.

When not installed correctly, composting toilets can release odors from the compost pile. This is caused by ineffective composting or inadequate ventilation.

If the composting toilet chamber is not regularly removed, the toilet can become clogged

Sometimes people install the wrong composting toilet system in wrong location.

Note: Wet composting toilets are best located away from a dwelling, while dry composting toilets are more suitable under houses.

Using a Compost Toilet

It depends. The frequency of cleaning depends on the size of the compost toilet unit and how often it is used. Using natural or eco-friendly cleaning products is suggested. Chemicals are, in fact, dangerous to the composting process and should never be added to a composting toilet. 

You only have to clean the bowl (in a central system) or the bowl liner (self-contained unit) as you would a regular bowl, except without the use of chemicals.

Waste chutes can be cleaned by wiping the surface clean with a natural spray. Any paper used can be put down the composting toilet. Obviously using a bio-degradable or recycled paper is best.

There are a few very convenient uses for compost toilets. These include but are not limited to:

  • Off grid homesteads
  • Vacation cabins
  • RV’s and caravans
  • Tiny Homes

Urine accounts for about 85% of the waste volume and in urine diverting toilets, is routed separately away from the composting toilet. This increases the storage capacity for solids greatly.

You can use normal toilet paper. However we do recommend not using highly quilted multi-ply paper as it takes longer to decompose. Actually this helps keep the contents of the container dry and divided which facilitates the handling after the storage period.

People don’t tend to compost within the solid waste containers that are supplied with their composting toilets. Typically when the compostable liner bag is about 2/3 full, it should be removed from the toilet and placed within your compost area, incinerator or approved solid waste disposal area.

Bags should be removed within a month of being put in service, as they will begin to weaken. The bags can be removed from the toilet along or within the solid waste container for support of the bag if needed.

Yes. Compostable waste bags specifically for composting toilets are recommended. This is because these waste bags are designed to endure the conditions inside the toilet and during the storage period. The bag will slowly disintegrate in the ground or in a composter.

This keeps the housing dry and extends the lifetime of the fan. If the fan has to be switched off, place the lid on the container and remove it. Otherwise, bad odors will spread indoors and flies can easily enter and lay eggs.

The approvals for building, plumbing and composting may vary between cities, provinces, states and countries. Details concerning the need of permissions can be given by you local environment and health office.

Like brakes or tires on a car, certain parts eventually need to be replaced. On Sun-Mar toilets, the fan and the thermostat usually fail after a number of years. In both cases the parts are inexpensive and are easily accessible for you to repair.

The noise of each fan will vary. Most are only as noticeable as room roof fans. Make sure you read reviews from those who have installed a particular composting toilets to see if they comment on any fan noise. Given the fan needs to be on all of the time, a loud fan may drive you a little crazy.