The water closet, often referred to as toilet, has a long history and an almost as long a list of problems.
Flush toilets use an enormous amount of water. Usually toilet water is potable and the use of it leads to lower availability for drinking, which can worsen or cause emergencies.
It takes more water to process waste than to carry it away, and that water is not all gray or already polluted.
- Don't use potable water, gray water from the dishwasher and laundry tub can be used in a toilet with no loss of functionality.
- Use a low flow toilet, but not yet one made in North America. The Australians have mastered the art of low flow toilet. The Australian designs use a different method of flushing, and separate levers for liquids and solids.
- Use recycled water, a solar treatment system can evaporate water from the waste, collect it and use it for the next flush.
- In a rural setting, anaerobic waste treatment is still very common. It's easy to install and maintain, but it's woefully inefficient. Besides inefficiency, it potentially leaks untreated wastes into the water table, poisoning the drinking water for whole towns. An aerobic digester is much better, though it is much more complicated.
- Composting toilets are basically outhouses but with more modern design that prevents offensive odours and disease spread though constant flow of air.
- Some people put low density porous objects (bricks) in their toilet cisterns. This displaces some water and consequently reduces the amount of water available for each flush. Though the technique works quite well in many cases, those with substandard plumbing will just end up flushing more often.