I need to replace my leaking steel expansion tank on my 175,000 btu output residential boiler. The existing tank is on the supply side, has a shut off to isolate it. Is it ok to install a new bladder type tank where the old one was? It would be in a dead end location but do have a float type air eliminator in the system. I can't install it as the diagram from the tank shows. My circulator pump is plumbed into the 1 1/2 pipe coming out of the boiler then goes to the supply manifold that make up the different zones and the offshoot to my old expansion tank.
You should repipe the boiler. If going to return side add it before the circulator . tied in with feed water with reducing valve and back flow preventer. Install air separator on supply. There are other ways to pipe that may meet your needs, Best to have a pro evaluate what is best for you.