Hello,

I have a house built in '29. Hot water boiler with cast iron rads. Boiler is a 1990 peerles, gas.

My 2nd floor rads always have a little bit of air in them- all of them. For example, if I check them every couple of weeks they will bleed out a little air when I crack the bleeder.

Downstairs never has any air, just water when you open the bleeders.

Is this normal?

PS the 2nd floor rads seem to work OK despite the air.

The boiler has a street water line feeding a regulator, a green expansion tank, and a pressure valve. Operating pressure is about 10lbs according to gauge.

It could be normal since it takes a long time to cook out the intrained air that is present in water. Heating the water also helps to release the same air as mentioned before. All air in your system usually ends at the highest point that is whay I always put an auto vent at the highest point to have a automatic air eliminator .

One last item the air could also come from your auto water feeder since the incoming cold water always has some air in it.