Shop Combustion Depot for your best online supply of MEPCO brand products. Marshall Engineered Products (MEPCO) are industry pioneers in the design and manufacture of engineered steam and hydronic solutions. From the first thermostatic trap perfected in 1903 has come the industry's most reliable line of designs, proven and tested in hundreds of thousands of buildings worldwide. From low pressure comfort to industrial process applications, Marshall Engineered Products Company (often referred to simply as MEPCO) produces with the lasting quality and operational longevity that exceeds the working expectations of other brands.