He was a Quaker like the Malcolmsons in Portlaw. In 1866, a Quaker Meeting House was built in Ashpark at a cost of £459 and the Grubb family opened an iron and coal business on the North Quay and subsequently developed a wholesale and retail trade in corn, flour, oats etc. in the building at the junction of New Street and Greenside. The building still has the letters JG & S 1907 on the side facing the Garda Barracks. John Grubb died, a relatively young man, in 1870 and the aforementioned eldest son Joseph Ernest took over the business. He decided to diversify and became involved in the milling industry, building a corn mill at the New Bridge. The Grubb family recognised the river Suir as a commercial highway and three generations of the family, including Joseph Ernest, held the position of secretary of the Suir Navigation Company. Joseph Ernest also established the Suir Steam Navigation Company, an export-import business operating through the port of Waterford and based on a combination of tug boats and flat-bottomed barges. Carrick-on-Suir and Clonmel acted as dispatching and collecting centres for their hinterland areas; goods, parcels and livestock were brought to Waterford for forwarding on by arrangements with the Waterford Steamship and Clyde Shipping companies. The non-tidal stretch of river between Carrick and Clonmel was navigated by flat-bottomed barges pulled by a team of twelve horses, accompanied by a team of men on a specially constructed towpath.
Through his involvement in local politics, Joseph Ernest Grubb found a means of putting his Quaker principles into action, especially his views on equality and justice. From 1878, he was a member of the Town Commissioners and following the Local Government Act 1898 he continued as a member of the Carrick-on-Suir Urban Council, and is the first name listed on the Chairman's Board in the Council Chamber. He was also elected to South Tipperary County Council and served as Chairman in 1911.
While attending a Quaker's Conference in London in 1927, Joseph Ernest Grubb fell, fracturing his hip. He never recovered and died peacefully; appropriately, he is buried in St. Mary's Cemetery, which he was involved in providing for the town of Carrick-on-Suir.