Finding the Main Vent in a home

crownboiler

At my parents house I'm struggling to find the main vent in the basement for steam heat. I've traced the main vent from the boiler room to a crawl space. The main vent goes into a crawl space which I've checked also but didn't go inside.

The house is over 90 years old and my parents have lived out the house for close to 40 years. Speaking with my father he tells me that he has never changed a vent in the basement.

Could the vent possibly have been replaced with a plug or pipe ?

Are there any tricks in finding a the main vent location ?

Can I remove a plug from a tee and add a main vent in the boiler room ? From being a member for 5 years and reading this website. My assumption is that this not advisable but since I can not find the main vent hopefully this be an alternative.

Thanks in Advance

Fred

Is this a one pipe or a two pipe system? (Is there a pipe on each side of the radiators or just one pipe/valve one one side and a radiator vent on the other side of the radiator?) Typically the vents are either at the end of a Main or on the dry return. Pictures of the boiler, the piping around the boiler and of a typical radiator will help people on this site help you.
It is possible there are no vents on this old system or that they were removed and a plug put in their place. Proper Venting will help move steam faster and reduce fuel costs.

crownboiler

Thanks Fred for the quick response, this is a one pipe system.

Will take pictures shortly.

Big Ed_4

Depends .. Is the return wet or dry if its above the water line all the way back when it returns into the boiler room it's called an dry return and an main vent could be install above . Wet return the main vents are at the end of each main .They are in the crawl space ? You can instal an King vent at the last radiator . King vent is an main vent teed off the supply of the radiator in the room .

crownboiler

Thanks BigEd