The deceased S Dinesh of Vetri Nagar had been hired with his helper Selvam by the house owner Robin Moses, said police.
The incident happened on Friday at Krishna Nagar. Dinesh who was drilling holes in the tank to fix the water level controller suffered an electric shock and collapsed.
He was rushed to a nearby hospital and sent to Kilpauk Medical College Hospital after first aid. However, he was declared brought dead at KMC and the body was sent to mortuary.
On information, Thiru Vi Ka Nagar police registered a case detained the land lord and two others for inquiry.