SEN0204 - Sensing capacity

Hi,
I stumbled upon this sensor when looking for a solution to monitor fresh and wastewater tanks in a motorhome with an arduino or raspberry pi. My tanks are generally rectangular and 75-100 gallons. My question is ... In order to monitor levels in each tank how many of the sensors would be required per tank if I would like to display in gallons and not if it is 1/3, 2/3 or full? For instance the one tank is about 18" tall by 28" wide and 48" long. All are either ABS or polyethylene.
Thanks,
Scott
I stumbled upon this sensor when looking for a solution to monitor fresh and wastewater tanks in a motorhome with an arduino or raspberry pi. My tanks are generally rectangular and 75-100 gallons. My question is ... In order to monitor levels in each tank how many of the sensors would be required per tank if I would like to display in gallons and not if it is 1/3, 2/3 or full? For instance the one tank is about 18" tall by 28" wide and 48" long. All are either ABS or polyethylene.
Thanks,
Scott