what is this component of my furnace system?

[vshah]

Found a nasty leak in our steam furnace today - coming from the base of this green tank thing behind the boiler. what does this thing do? is it just a reservoir for the system to contain the water when the system is idle?

we're in a rented apartment - this leak happened after the hvac guy came to replace the old pump that was shot.

 

[Paperdoc]

Yes, it is a reservoir or surge tank, and it is partially full of the circulating liquid (I assume just water). It ensures that the system never runs dry suddenly - there is a separate system that checks the tank liquid level and adds more water if needed. But its main function is to allow for expansion. As the system heats and cools, different rates of expansion for the water and the piping mean that the liquid level in the tank fluctuates slowly up and down, If there were no such tank with an air pad, the differential expansion would cause substantial stress on the piping components.

The second pic shows significant corrosion, no doubt leading to the leak. It should be replaced. I would expect that's the landlord's responsibility.

 

[SpatiallyAware]

Yes, it is a reservoir or surge tank, and it is partially full of the circulating liquid (I assume just water). It ensures that the system never runs dry suddenly - there is a separate system that checks the tank liquid level and adds more water if needed. But its main function is to allow for expansion. As the system heats and cools, different rates of expansion for the water and the piping mean that the liquid level in the tank fluctuates slowly up and down, If there were no such tank with an air pad, the differential expansion would cause substantial stress on the piping components.

The second pic shows significant corrosion, no doubt leading to the leak. It should be replaced. I would expect that's the landlord's responsibility.

And if the landlord tries to push back just whisper "mold test" into the phone. It will likely be fixed immediately.

 

[vshah]

Its been replaced, although the new one is much smaller... About the size of a propane tank

 

[dmcowen674]

Its been replaced, although the new one is much smaller... About the size of a propane tank

That's the norm. That green one was huge.

 

[Paperdoc]

I agree with dmcowen674 - my mother-in-law's is smaller than a propane tank.