I have a Taco 007 with a blown cartrige. I'd like to get a replacement for it. I've been looking at various on-line stores and I can't believe what I'm finding for prices, shocking. I can actually buy a completly brand new 007 circulator at the local big box store for just a little more $$ than what the cartrige costs. What's the deal? Can anyone direct me to a source for a replacement cartrige. I can't believe that the cast iron housings are considered disposible.