How do I replace a heater circulator pump?

Answer 1

Unless you really know what you are getting into, call a professional for this job.

Answer 2

If you're talking about a hot water system circulation pump, the last one I replace had six bolts holding two separate flange sets together. Shut the water supply off, remove the old pump, install the new pump and gaskets, tighten bolts, turn on water. Fairly simple. Sometimes the hardest part is finding the right pump. Most any decent plumbing/heating supply house should have what you need.