A well-designed, well-maintained waterless toilet can be used to turn your toilet waste into compost ready for eventual use in your garden.

Waterless toilets do require more maintenance than a conventional toilet and they may be hazardous if they are poorly maintained.

Waterless toilets are not recommended for urban areas. If you have a connection to a mains sewer, you’re legally required to use it.

Why consider a waterless toilet?

Waterless toilets can be used as an alternative or addition to other on-site sewage systems. They can be used on sites where mains sewage connection is not an option, and other on-site systems such as septic tanks, aren’t practical (for example, because there’s no room for a soakage area).

A waterless toilet will also save significant amounts of water, which will reduce your costs if you are on metered  or limited water supply.

Types of waterless toilet

The most common type of waterless toilet is referred to as a ‘composting toilet’. Composting toilets work by separating liquid and solid waste; the liquid is evaporated off leaving the solid waste for composting.

There are two main types of composting toilet:

• Continuous composting toilets - these have a single container beneath the toilet where waste is held for up to a year until it has decomposed and can be used as compost.
• Batch composting - these have two or more containers, one that’s in use while the waste in the other decomposes.

For each type, there is a wide range of models available. You can buy an off-the-shelf unit, or you may be able to build your own using readily available materials.

With both types, after the waste has broken down into compost it needs to be removed and buried in an area of your garden away from general use and any food plants.

Legal requirements

Under the Building Code, if your property is connected to a mains sewer you must use it.

If you are installing a waterless toilet, check with your local or regional council first. You’ll need a building consent for the toilet structure, and you’ll need to check that the toilet you’re considering has approval in your area. Council attitudes and regulations vary. You’ll also need to show that you have installed an appropriate system that can be maintained to an acceptable standard.

Because of the risks associated with inadequate maintenance, the Ministry of Health does not recommend waterless toilets in urban areas.

Maintenance

Waterless toilets require regular attention including some unpleasant maintenance such as raking, emptying and pest management. You will also need a large enough garden to dispose of the compost safely.

You’ll have to regularly add a bulking agent such as dry leaves or untreated wood shavings to the container. This helps to keep the product aerated promoting the composting process.

You can’t use chlorine bleach or other strong chemicals for cleaning.

Removing the compost

The compost has to be disposed of according to local council requirements - check with your council. It shouldn’t be buried in areas of the garden that are in general use or where food plants are grown, and it shouldn’t be put near streams or other bodies of water.

How often you have to remove it depends on the size of container, how often the system is used, and local climatic conditions. The compost process may require up to a year. Heat can be applied to speed up the process. Mixing also aids composting.

It’s important to check the quality of the compost: it must be dry and crumbly, with no offensive odour.

If your toilet is not working properly and you put the compost on your garden, contaminants (which could include campylobacter, cryptosporidium and giardia) could run off into neighbouring land and waterways. You are legally responsible for the safe disposal of effluent on your property.

Odour

A composting toilet that is working well does not smell. Keeping the toilet lid down when not in use will help with smell and reduce flies.

Offensive odours indicate that something is wrong and you should follow the trouble-shooting directions supplied by your composting toilet installer or supplier.

Greywater

If you’re planning to install a waterless toilet to deal with all of your toilet waste, you’ll still need another on-site system to safely deal with wastewater from the kitchen, laundry, bath, shower and basin.

More information

From Smarter Homes

• Maintaining your on-site sewage system
• Choosing an on-site sewage system
• Reducing water flow
• Reusing greywater
• Collecting and using rainwater
• Managing stormwater
• Outdoor water use
• Onsite sewage systems

From ConsumerBuild

• Building consents

Your local or regional council will have information about on-site sewage systems in your area. Consumerbuild’s Council finder web page has contact details for New Zealand local authorities.

From other sites

For general information on composting toilets see http://www.compostingtoilet.org/. This site is sponsored by a Canadian composting toilet manufacturer.

You can buy copies New Zealand Standards relating to on-site sewage systems and waterless toilets from the Standards New Zealand website.