[5] Upon completion of the Calcutta water project, MacRitchie spent seven years working for the Japan government as Lighthouse Engineer.
According to his obituary, published in Singapore, he was responsible for designing and building lighthouses around the coast of Japan and is said to have been the last foreigner to have held this position.
He was responsible for numerous works and immense improvements in the streets, bridges, public markets, abattoirs and other infrastructure in Singapore.
MacRitiche was the architect for the new cast-iron octagonal-shaped Lau Pa Sat market (now a national monument) which was relocated to its present position in 1894.
MacRitchie applied himself to the problem of night soil and studied various alternatives for Singapore including a pneumatic system and conversion to 'poudrette'.
The Municipal Commission sent him on a 3-month fact finding trip to India in 1893 to inspect sanitation, night soil and water supply systems and to bring best practices back to Singapore.
The report he prepared had 'all the data and, in many cases, the worked out detail for dealing with the sewage and refuse of Singapore' and was described as 'a valuable contribution to municipal engineering in the East'.
MacRitchie noted that the demand for water had more than doubled from 1.4 million gallons per day in 1885 which explains the enormous value and importance of the Impounding Reservoir.