Utility systems are composed of water and waste systems, as shown in Figure 15.39. Passengers need water and restroom facilities. As the number of passengers and the duration of flights increase, the demand for drinking water and waste-disposal management also increases. The entire system is self-contained.
Typically, a third of a U. S. gallon of water per passenger (i. e., 100 U. S. gallons for 300 passengers) is the quantity carried onboard. Both hot and cold water is supplied. Typically, 1 lavatory per 10 to 15 passengers is provided. Chemicals are used
with water to flush the commodes. Waste must be contained inside until the aircraft lands, whereupon the systems are cleaned and refilled with fresh supplies for the next sortie. Figure 15.40 shows the RJ family wastewater-management system in detail.
Aircraft must be prepared for passenger services and utility use. Specific locations are designated for preparing aircraft such that they do not interfere with and delay one another. Figure 15.41 shows the typical utility-service points. Access to servicing should not interfere with other activities in and around aircraft. Freezing of water is prevented by heating the critical areas.