Camión Cisterna, Camion Aljibe.

Tank truck, tanker (BrE).
The company has got about eight tank trucks.

Reference in News:

"The driver of the septic tank truck, Leonard Salcido, 24, of Tucson, was arrested and booked into the Santa Cruz County Jail on charges of possession and transporting marijuana."
http://www.kold.com/

"A tank truck carrying 8,000 gallons of gasoline caught fire Friday morning on northbound Route 222 near an exit ramp to Route 61 in Muhlenberg Township, forcing police to stop traffic on both highways for fear the tanker might explode."
http://readingeagle.com/

"A Fonterra spokesperson said the driver of the tanker was taken to hospital for a check and would be offered counselling."
New Zealand Herald