Controller Water supply in-line heater (SAT 2129, WL 189, LBL 8) Remote temp sensor (SAT 2171, WL 200, LBL 52) Controller Water supply in-line heater (SAT 2133, WL 189, LBL 8) Remote temp sensor (SAT 2171, WL 200, LBL 52) Controller Water supply in-line heater (SAT 2079, WL 155, RBL 49) Water tank drain heater Controller Water supply in-line heater (SAT 2127, WL 189, LBL 3) Remote temp sensor (SAT 2144, WL 203, LBL 80) P320 ground service/handling power panel Note: Heater off when temperature is > 60 °F (15 °C) Heater on when temperature is < 45 °F (7 °C) 115V AC ground service bus Water supply Line heaters 15-32 Figure 15-47.  Water supply line heater system. Figure 15-46.  Chemical deicing spray tubes.  Water and Waste Tank Ice Prevention Chemical As previously mentioned in this chapter, chemical anti-ice  systems exist generally for small aircraft. This type of anti-ice  is also used on windshields. Whether alone or part of a TKS$^{TM}$  system or similar, the liquid chemical is sprayed through a  nozzle onto the outside of the windshield which prevents ice  from forming. The chemical can also deice the windshield  of ice that may have already formed. Systems such as these  Large aircraft equipped with pneumatic jet blast rain repellant  systems achieve some anti-icing effects from operating this  system although electric windshield heat is usually used. Transport type aircraft have water and waste systems on  board, and electrical heaters are often used to prevent the  formation of ice in the water lines of these systems. Water  lines carry water from the potable tanks to the lavatories and  galleys. The waste water tanks collect the gray water from  the galleys and lavatories. Heater blankets, in-line heaters,  or heater boots are often used to heat the water supply lines,  water tank drain hoses, waste drain lines, waste tank rinse  fittings, and drain masts. Thermostats in the water lines  supply temperature data to the control unit that turns the  electrical heaters on and off. When the temperature falls  below freezing, the electrical heaters turn on and stay on until  the temperature reaches a safe temperature.  Figure 15-47 is a schematic of a water supply line heater system, and  Figure 15-48  shows the location of the waste water tanks  and heater blanket. have a fluid reservoir, pump, control valve, filter, and relief  valve. Other components may exist.  Figure 15-46  shows a  set of spray tubes for application of chemical anti-ice on an  aircraft windshield.