This manual was created by O-E Specialty Manufacturing Co. and outlines how to install the "O-E" Perfect System, which is a Vapor Vacuum heating system.
Phelps Tee Patent
One of the earlier gravity-hot-water-heating devices. Water would stratify in the horizontal main, with the hottest water rising to the top of the pipe. It left the tee and flowed to the radiator though the tee's top tapping. Cooler water from that radiator entered the same tee though the side tapping. Interesting things happen when you add a circulator to a system that has these tees. Thanks to Gerry Gill for finding and sharing the patent.
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