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Clow Darling About Us

Experience Matters

Clow Darling started business in Fort William (now Thunder Bay) in 1937 when Bill Darling and Emerson Clow purchased the local branch of Darling Plumbing & Heating of Winnipeg.
The Head Office of Clow Darling Limited is located at 1201 Cameron Street in Thunder Bay, Ontario .
We are signatory with the following unions: Air Conditioning Local 787, Boilermakers Locals 128 and 555, Ironworkers Local 759, Labourers Local 607, Millwrights Local 1151, Operating Engineers Local 793, Plumbers and Pipe Fitters Local 628, Sheet Metal Workers Local 397 and Sprinkler Local 853.
  • Overview
  • Started in Winnipeg
  • Purchased in 1937
  • Expanded Post War
  • Took on Large Projects
  • Now largest full-service mechanical contractor in NWO

Over the last several decades our work has included:

  • Plumbing and heating during construction of the Hawker Siddeley Aircraft plant
  • During the post war industrial growth, Clow Darling expanded its mechanical services with contracts on the Pine Tree Radar project throughout northern Canada, and several mines in Northwestern Ontario.
  • During the 1960’s, Clow Darling undertook several large institutional projects including the construction of McKellar Hospital.
  • During the 1970’s and 1980’s, Clow Darling was a major contractor, completing multi-million dollar projects for the paper mill industry throughout the region.  We also completed several large apartment buildings and senior citizens complexes, residential housing developments and large institutional projects.
  • During the 1980’s, we expanded our service department and undertook work in the fire protection, air conditioning and refrigeration market.
  • During the following decades, Clow Darling continued to grow to become the largest full-service mechanical contractor in Northwestern Ontario.  Current owners are Barry Leochko, Gerald Kelly, Eric Niemi, John Cava, Mark Sandberg, Mark Lagrange, Andrew Ramsay and Paul Maydo.

Commitment to Quality Award


We are very proud to be the recipient of the 2017 Commitment to Quality Award, presented at the 23rd Annual Thunder Bay Chamber of Commerce Business Excellence Awards. As the largest full-service mechanical contractor in Northwestern Ontario, we have worked hard to ensure our customer service efforts and project management skills grew along with us to maintain the high quality of work we have always been known for. Thank you to the Thunder Bay Chamber of Commerce for the recognition!

Recent Projects

2008/09 – Biomass Boiler erection for Abitibi Bowater in Fort Frances (Industrial)

2010/Present – Dawson properties – High Efficiency Boiler Conversions throughout multiple buildings.( Commercial)

2014 – Plumbing and Heating at the New OPP station and MNR building in Armstrong.

2014 – Greenstone Structural – Process Steam system for Manufacturing plant

2014 – Main contractor for Cold Shutdown at Resolute Thunder Bay (Industrial)

2015 – Propane to Natural Gas conversion for Goldcorp Red lake (Industrial)

2010 – Present – Hi Efficiency Boiler Conversions at numerous schools throughout the Lakehead District School Board including the Main Board office. (Commercial)