This morning I noticed a very old, closed, steel expansion tank in the boiler loop is leaking. Looks like the leak is coming from the side of the tank and not from the plumbing. Not sure if that can be repaired or replaced easily so was wondering if a more easily found diaphragm expansion tank could be used instead.
I have a Weil McLain CG series gas hot water boiler system. The manual shows two different setups for when using a closed tank or a diaphragm tank.
My system isn't set up with the expansion tank in either of those configurations. What I have looks like this.
There's no pressure regulator on the main incoming water line and therefor the hot water heater doesn't have an expansion tank on it but at some point I'd like to add both.
I do have an automatic air vent in place on top of the boiler.
Can I just replace the steel expansion tank with a diaphragm expansion where it is? How important is the placement of the tank in the heating loop? Getting it connected under the circulator as shown in the diagram would be a real pain. I was planning on shortening the piping run to the old tank and placing it along that run.
Best Answer
The old tanks had to be pressurized to provide an air space the newer bladder based systems are better in my opinion and will work fine as long as rated for the temp/pressure.