wels, and old cotton socks are acceptable. If the composter is to be used season- ally, unplug the fan before you shut down the house. If the weather is cold when you want to start up the composter again, it may take some time to start things cooking. Depending on the temperature LOW-IMPACT SYSTEMS Kitchen Utility Bathtub Bathroom Laundry Toilet Shower To Grey Water System To Black Water System Figure 7.11 Grey water system components. and extent of disuse, you may have to add some bulking agent and some water to start the decomposition process. GREY WATER SYSTEMS Application All of the wastewater that comes out of a house that doesn't come from the toilet is called grey water. The toilet wastewater (and some- times the garbage disposal wastes) is called black water. Normally, the pipes collecting grey water and the pipes carrying black water are joined under the house and both types of waste are combined before they reach the septic tank. But if the pipes are kept separate, the black water and grey water can be treated differently (Figure 7.11). Under most circumstances, grey water is not as much a threat to health and environmental quality as black water (Table 7.3). Grey water is therefore a better candidate for reuse than is black or com- bined black and grey water. But be advised that grey water has been shown under certain circumstances to harbor more pathogens than are normally found in combined wastewater. It is not the benign material many people would like to believe, particularly when pro- duced by a household with infants or sick individuals. Reuse can be as simple as irrigating fruit trees or as complex as returning cleansed grey water to the toilet reservoir. There are even ONSITE WASTEWATER DISPOSAL systems which can turn grey water into pure drinking water, but these are too expensive for most homeowners. There is always a system parallel to the grey water system to handle the excreta (urine and feces). This may be a composting toilet, a holding tank, a conventional septic tank and drain field, or