TOPIC: Can anyone tell me what this tank is for?

I think that sounds logical Jeffrey, I am not doing the inspection on this house and the house has been remodeled and updated several times. I will investigate more and see if there are or have been any radiators in the house. Thanks for your insight.

I have no idea and am also wondering what the circular object on the left is as it appears to have been a port into the home at one time.
Which room is this behind?
How many stories tall is the home as it may have been used for water pressure?

I do not see why they would hide an expansion tank.

Other wise just go with Nitrous oxide.

Bob, it sorta resembles Transite, so am assuming it is where the boiler flue exited the home.

OK
Columbo. Lol

The cavity where the tank was found backs up to the living room and it is a single story house. There is a transite vent pipe that is to the right of it that come from under the floor and goes through the ceiling. There is also a brick flue chase above the tank but I don't think it has anything to do with the tank. Above the tank in the brick is a chase through the brick for a stove pipe that is sealed off. Thanks for all your input on this, I will be there again in a few days and will get more info to put up here for discussion.

I just had another thought. Maybe they were moonshiners and this was part of a still during prohibition.