full site glass

[fast pasquale]

i have a boiler in a 1929 rental.. the boiler is about 8 years old.. i have a two pipe system. I noticed today that the site glass was full. i opened the "flush out" boiler drain and let out about 3 gallons of water. it dropped to half full again. I notieced this happend last year on the other side of the house (it's side by side duplex)... probally just a coincidence????... anyways if it makes a diffrence... i closed the water water off to this side of the unit and shut the boliler off (via the switch).. about 2 weeks ago... ...Thanks so much for any help...