Fill Site Operations and Water Loading
Site selection and setup
Choose a fill site with firm, level access, room to turn, and a one-way traffic pattern that keeps tenders from backing into traffic. Keep the fill point away from overhead wires, drainage pathways, and public traffic. At a hydrant, use a gate valve and a large fill line; at a draft site, use hard suction with a strainer and adequate water depth. The fill pumper supplies the tender's fill connection, and the tender's vent must be open and clear. Monitor the tank level and overflow rather than relying on a whistle or guesswork.
Controlling the fill
Open valves slowly to avoid water hammer. Do not overpressurize the tender tank; the fill line should not be asked to withstand more pressure than the tank and vent can safely handle. Keep radio contact with the fill-site supervisor, and release each tender only when the tank is full and the hose is disconnected.
Worked example
A 2,000-gallon tender fills at 500 gpm, so the theoretical fill is 4 minutes. If a restricted vent or small fill connection limits actual filling to 300 gpm, the fill takes 2,000 / 300 = 6.7 minutes. Reasoning: the pump's rated capacity does not set fill time; the weakest point in the fill path does. A 2.7-minute increase per trip can require another tender in the shuttle.
Traps
Do not fill through a closed tank valve or a blocked vent. Do not use the overflow as the only full-tank indicator. Do not let tenders block egress or park under power lines. Do not leave a fill line pressurized after disconnect.