Gravity-return steam system???

Ok, for the second time this year, And the second time ever, I came across a two pipe steam system with air vents on every radiator. The first one looked similar to the gravity-return system Dan describes on page 125 of the Lost Art.


This second one, I can't seem to figure out what the installer was thinking. There are no thermostatic or F&T traps anywhere in the system. The return side of each rad is hard piped(no return ell, no union); so I don't believe an orifice is installed. The return mains are above the water line of the boiler (3/4"). The returns from some of the radiators are trapped with a dirt leg like I would install on gas piping for a boiler. I attatched a photo of one of these traps.

At this point, I will be repairing one leak on the return piping. The homeowner has reported no problems besides the leak. I found the system to be loud(hissing from air vents).

Any insight, experience, guesses, thoughts, or opinions would be greatly appreciated.

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