2 Pipe System w/ Radiator Vents?

Mark S.

I have an older house (circa 1911) with a low-pressure 2 pipe vapor system. The boiler was replaced in 1985. What has me confused is that all of the radiators have the bullet-type air vents, and the system does not have any main vents. Is this proper? Any insight would be appreciated!

Jacob Myron_3

@ Piope vapor system

That depends.

Most of these systems had one master vent near the boiler.

It was a large cast iron fitting with a a vent on top.

Some systems (wet return) had main vents at the end of each steam main.

Some systems (Vapor Vacuum) Only used radiator vent valves.

Since the systems today are not coal fired vacuum in the system can cause operational difficulties.

You can install main ven vents on the end of the steam mains to help remove air from the system quicker. The end of the steam main should be at least 27" above th eboiler water line.

If the system works well leave it alone. Some times the fix is worse than perseave problems.

Jake.

Steamhead

I've run into that

and the system is usually making all kinds of strange noises..."oh they all do that!" Wrong.

But before making any changes we need to know what type of Vapor system this is. Have you noticed any strange-looking things in the piping around the boiler? Any manufacturer's names on equipment that looks original? Can you post some pictures?

Most Vapor systems vent the air from the radiators into the dry return (along with the condensate) and out thru a large vent or trap at the end of the dry return. Adding radiator vents to these systems is a sure way to screw them up.

There was such a thing as a 2-pipe air-vent system. It had shutoffs on both the supply and return radiator connections, and an air vent on each radiator. This is NOT a Vapor system since the air does not go thru the dry return to be vented. You vent the radiators and steam mains on this type of system the same as on a one-pipe system.

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