William Patrick Collopy was born in Liverpool, Lancashire, England on 2 February 1890.

He was the son of Irish-born William Collopy, a seafarer, and Elizabeth Hall, a native of Liverpool. He had two elder brothers and a younger sister.

By the time of the 1911 census, taken a year after the death of his mother, William was living at 10 Wellbrow Road, Walton and was described as an unmarried marine steward; he first appears on crew manifests in April 1909 when he was a steward aboard Menes, later working aboard Venetian by the following year.

In April 1912 he was serving as a waiter aboard the eastward-bound voyage of the Carpathia when that ship rescued the survivors of the Titanic. 

By 1913 Collopy was working aboard Cretic, his ship prior to that being the Adriatic, and with the outbreak of WWI he continued working at sea with the merchant fleet.

He was married at St Luke's Church, Walton, Liverpool on 28 February 1915 to Grace Emily Kempton (b. 1890), a schoolteacher, and they had a son the following year, John.

They lived for many years in Liverpool but relocated to Sholing, Southampton in the 1950s.

William Collopy died in Southampton on 15 July 1972 and his ashes were scattered in South Stoneham Cemetery. His widow Grace died four years later.