John R. Leal saw service in a number of areas during the Civil War including Folly Island during the Siege of Charleston, South Carolina.

[1] He contracted a chronic case of amoebic dysentery (most likely from contaminated drinking water) at Folly Island from which he suffered for the next 19 years before the disease caused his death in 1882.

He also oversaw the public water supply and was responsible for constructing the growing network of sewers to remove domestic and industrial wastes from the City.

To prevent the spread of contagious diseases, he was responsible for building an Isolation Hospital in Paterson in 1897, which, at the time, was considered a model facility.

His decision to focus on matters of public health and the safety of drinking water was driven in part by his personal experiences and from the influence of Garret Hobart, who became the 24th Vice President of the United States in 1896.

Despite his concentration on water treatment affairs after 1899, he was still involved in the Passaic County Medical Society, serving on the Legislative Committee in 1900 and in 1901 he was President.

[11] In 1899, Jersey City entered into a contract with Patrick H. Flynn to build a water supply to replace the one that was significantly contaminated by sewage.

A large dam was built on the Rockaway River which resulted in the formation of Boonton Reservoir that had a capacity of over 7 billion gallons of water.

Included in Leal's responsibilities was the removal of illegally constructed privies and other obvious sources of sewage contamination from the watershed above Boonton Reservoir.

In his final decree dated June 4, 1908, Stevens ordered the JCWSC to pay for the construction of sewers to remove contaminants from the Rockaway River watershed or create "other plans or devices" which could be used instead to produce water of the required purity.

As Health Officer for Paterson, Leal used solutions of chloride of lime (calcium hypochlorite) to "disinfect" homes where scarlet fever, diphtheria and other communicable diseases were found.

In 1897, high concentrations of chlorine derived from chloride of lime were used to disinfect the reservoir and pipelines of Maidstone, England, after an outbreak of typhoid fever.

[12] On June 19, 1908, Leal hired George W. Fuller to construct a chlorination plant at Boonton Reservoir to disinfect the water for Jersey City as a representation of "other plans or devices".

[15] Fuller based his design on the successful aluminum sulfate feed system that he had built at the Little Falls Water Treatment Plant in 1902.

The purpose of this trial was to determine if the chloride of lime system that had been installed by JCWSC was effective in controlling harmful bacterial levels and capable of providing water that was "pure and wholesome".

The record shows that Leal came up with the idea to disinfect the water supply of Jersey City and he should be given the credit for this major advance in public health.