fuel water checks
fuel tank water checks need to be completed after every refuel.
but it needs to be done after the fuel has settled after refuelling or the aircraft has remained stationary for 0ne hour
therefore cannot be completed on transits stops after fuel top ups, but left till the daily check at night.
OK on B777 as just 3 tanks but B747 has 8 tanks.
most A/C these days have pipes that suck fuel from the lowest point in tank and discharge it to the inlet for the main pumps, so water constantly scavenged from the bottom of tank, and water checks do not yield the gallons of water that B707 did.
fuel water checks were a bonus for the mechcanics in third world countries, as it was used for cooking, and a oil drum of fuel would disappear into the jungle after aeroplane choxs off.