In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Expansion Tank fails repeatedly
I have a setup for radiant floor and DHW running on a Munchkin boiler. It all works great, with one exception. In five years I've gone through 3 expansion tanks! Each time, the tank fails by rusting through from the inside. I cannot believe I would get 3 defective tanks (they were bought at different times, from different vendors, but all same manufacturer).
I've tried to include some photos to show the setup.
Here is my theory: the tank that fails is at a low spot in the system (not the lowest spot, but close). The boiler and DHW are connected with black pipe, and the radiant zone pumps with copper. There are proper dielectric unions between them. Perhaps the iron pipe is corroding slightly, and the sediment is falling into the expansion tank, somehow causing excessive corrosion inside the tank? Does this make sense?
So, do I replace all the black pipe with copper? I am afraid there may be damage to the boiler that I cannot see, because that is truly the low point in the system. Would a trap or filter solve the problem?
By the way, there are 2 expansion tanks on the system, one up high near the inlet and one near the radiant manifold. It is only the one near the radiant that fails.