How to Save Water by Using a Composting Toilet

How to Save Water by Using a Composting Toilet

What is a Composting Toilet?

A composting toilet is a type of toilet that treats human waste by composting or decomposing it, rather than using water to flush it away. Unlike a flush toilet, which uses gallons of water with each flush, a composting toilet does not require any water or a sewer connection.

Composting toilets work by separating liquid waste from solid waste and using natural processes to break down the solids over time. The liquids drain off into a leach field, while the solids accumulate in a chamber below the toilet seat. With the help of oxygen, beneficial microbes, and sometimes heat, the waste gradually decomposes until only a small amount of compost remains.

Some key advantages of composting toilets include:

  • Water conservation – No water is needed for flushing
  • Nutrient recycling – The composted humanure can be used to fertilize non-edible plants
  • Low maintenance – Less moving parts than a flush toilet
  • Off-grid functionality – Does not require municipal water or sewer connections

How Do Composting Toilets Work?

There are a few different designs of composting toilets, but most separate liquids from solids and provide ventilation to speed decomposition. Here is an overview of the basic composting toilet process:

Separation of Liquids and Solids

After using the toilet, solid waste drops into a chamber below the toilet seat while liquids drain off through a separate pipe. The liquid waste flows into some type of leach field or storage tank for future disposal.


Airflow speeds up the natural composting process. Vents allow fresh air to enter the solid waste chamber and carbon dioxide to exit. Fans can assist with air circulation. Oxygen helps aerobic bacteria thrive and break down waste.


Over time, aerobic bacteria, fungi, and other microorganisms digest and compost the solid waste. Larger particles get broken down into smaller ones. Temperatures may rise during active composting.

Removal of Finished Compost

Depending on use, finished compost can be removed after 6-24 months. Only a small amount of stable humus remains. The compost can be buried or used on non-edible plants.

What Are the Benefits of Using a Composting Toilet?

There are many reasons why I chose to install a composting toilet, including:

Water Conservation

Composting toilets use no water for flushing. The average flush toilet uses 1.6 gallons per flush. For a family of four, a composting toilet can save 27,000+ gallons of water per year compared to a standard toilet. This helps reduce strain on water supplies.

Nutrient Recycling

The compost harvested from a composting toilet contains nutrients like nitrogen, phosphorus, and potassium from human waste. This compost can fertilize non-edible plants. Though not a replacement for fertilizer, it reduces the need for chemical alternatives.

Lower Environmental Impact

By recycling nutrients on-site instead of using gallons of water to transport waste, composting toilets are gentler on the environment. They produce no sewage that requires energy-intensive treatment. The compost end product also avoids landfill disposal.

Off-Grid Use

Composting toilets require no outside water source, drainage field, or septic system to function. This allows them to work off-grid in rural cabins, tiny homes, or properties lacking municipal connections.

Odor Prevention

Properly maintained composting toilets produce little odor. Separating urine from feces and providing good ventilation prevents anaerobic conditions. Some models have extractors or negative pressure to manage smells.

What Are the Drawbacks of Composting Toilets?

While I am very happy with my composting toilet, there are some downsides to consider:

High Upfront Cost

Purchasing and installing a composting toilet costs significantly more than a standard flush toilet. Expect to invest $1000-$3000 or more depending on the model. DIY builds can reduce costs.

Space Requirements

Composting toilets require extra space for the composting chamber and solid waste storage. This limits installations in small bathrooms. Electric composting toilets have a larger footprint than self-contained models.

Regular Maintenance

To function properly, composting toilets need maintenance every few months. Tasks include raking/stirring compost, draining liquids, and removing finished compost. Neglect will create problems.

Limited Capacity

The composting chamber size and extraction rate limit how many users a composting toilet can support. Generally, each toilet works for a max of a family of four. More people requires installing multiple units.

Cold Climates

Composting slows significantly below 55°F. Heating units or moving indoor helps for winter use in cold climates. Otherwise, capacity decreases.

What Maintenance Does a Composting Toilet Require?

To keep my composting toilet working properly, I make sure to follow these maintenance steps:

Rake Compost

Every 2-3 months, I rake the accumulating solids with a special rake tool. This mixes waste layers and introduces more oxygen to aid composting.

Drain Liquids

I drain the liquid tank as needed, especially after periods of heavy usage. Full tanks can back up the separation drain.

Add Bulking Agent

After raking, I sprinkle in coconut coir or sawdust to balance the carbon and nitrogen ratio. Bulking agents prevent waste from compacting and improve aeration.

Remove Finished Compost

When the compost level nears capacity, I remove finished compost into bags for burial. This makes room for fresh waste. I remove compost about once a year.

Check for Odors

If I ever smell a musty or rotten odor, I immediately stir the compost to increase airflow. Bad smells signal anaerobic conditions that hinder composting.

Monitor Temperature

I check the compost temperature monthly. Temperatures between 100-140°F indicate active composting. Cooler temperatures mean I should rake the compost and add more bulking agent.

Regular maintenance like this optimizes the decomposition and keeps my composting toilet hygienic and pleasant to use all year long.

Frequently Asked Questions About Composting Toilets

Is it safe to use human waste as compost?

Research shows that when properly composted, human fecal matter is safe to handle and use on ornamental plants. Key steps are maintaining aerobic conditions during composting and allowing at least 1-2 years for thorough decomposition. The high temperatures achieved destroy pathogens. Safe handling and common sense precautions are also important.

How much compost can I produce with a composting toilet?

On average, one person can produce 25-40 gallons of compost yearly with a composting toilet. Larger capacity units or more users will produce more compost. The amount of finished compost depends on factors like capacity, humidity, and waste characteristics. Expect 2-6 gallons per person per year of usable compost.

Do composting toilets require electricity?

Basic self-contained composting toilets do not require any electricity. Models with heaters, ventilation fans, or compost extractors will need an electrical power source to utilize those features. But the natural composting process itself does not need any electrical input.

Can I install a composting toilet in an apartment?

Unfortunately composting toilets are challenging to implement in apartments and condos. They require direct ground contact for the leach field and proper ventilation that is difficult to achieve within a single apartment unit. Local codes may also prohibit composting human waste without proper permitting. A collective building-wide system would be more feasible than individual units in apartments.

What temperature range do composting toilets require?

Composting toilets work best with average temperatures between 55-90°F. Below 55°F, the biological activity slows considerably. Heating units or moving a toilet indoors in winter can help for use in cold climates. Above 90°F, extra ventilation helps remove excess heat and moisture. With proper management, composting toilets can work year-round in most climates.


Installing a composting toilet has allowed me to reduce water usage, recycle nutrients, and minimize the environmental impact of my household waste. While composting toilets require more investment upfront and periodic maintenance, the benefits for sustainable living make them an option worth considering. With some education on proper use and care, composting toilets offer a practical waste management solution wherever flushing waste with water is difficult or wasteful. This ancient sanitation technique has evolved into an elegant water-saving solution for modern times.