Steven Greenaway charged one woman £1,527 for work and materials an expert estimated should have cost no more than £164 while another woman had an invoice for £787 for 40 minutes work.
Greenaway, who was spared a prison sentence in 2012 after he charged a vulnerable 78-year-old Oldbury man £2,000 to repair a leaking tap, wiped away a tear as he was led away to begin his spell behind bars.
Judge Michael Challinor told the 41-year- old his seven victims had been "seriously overcharged for something inadequately carried out or unnecessarily carried out."
He said Greenaway, of Marlpool Lane, Kidderminster, had clearly selected his victims because he believed they would be susceptible to the exaggerated bills he was handing out for his plumbing work.
The judge said there had been financial harm but he had left his victims "shocked and dismayed at being deceived in their own homes."
Greenaway used his status as a self-employed plumber responding to emergency calls to defraud his customers by grossly overcharging for work and materials.
He pleaded guilty to 13 fraud charges and asked for one other similar offence involving a Dudley woman to be taken into consideration.
A toilet in the woman's downstairs bathroom was blocked and Greenaway gave her an invoice for £489 before saying he needed a further £780 for materials which he was given in cash.
Mark Jackson, prosecuting, said a woman living in Barrs Road, Cradley Heath, was given the bill for £1,527 after discovering a leak in an outside toilet while a woman in Meres Road, Halesowen, was charged £787 for fixing a leak.
Christopher O'Gorman, defending, said Greenaway had been struggling financially and was now employed as a despatch rider.