The United Operative Plumbers' Association of Scotland was formed in 1872 after the members of the Glasgow lodge broke away from the United Operative Plumbers' Association of Great Britain and Ireland, on the grounds that their funds were being eaten up by English lodges. In 1891, members of the Aberdeen, Coatbridge, Dundee and Edinburgh lodges joined the Scottish Association, bringing in a total of 350 members. By the end of the nineteenth century the union had lodges scattered all over Scotland, with 1,257 members. In 1920, talks began on unifying the Scottish and English associations, and the merger became effective in January 1921 with the Scottish Association joining the United Operative Plumbers and Domestic Engineers' Association of Great Britain and Ireland.
The Scottish Operative Plumbers' Protective and Federal Benefit Union had originally been formed by a break away from the United Operative Plumbers' Association of Great Britain and Ireland in 1891. It later joined the United Operative Plumbers' Association of Scotland at an unknown date.
Reference: John French 'Plumbers in Unity' (1965).