When the heat goes on I can hear gurggling in the pipes which I assume
is air in the FHW system. I want to bleed this air off but am not
sure on how to go about it. It is a 3 zone system with 3 circulating
pumps. There are valves positioned on the return lines above each
pump. They look like outside faucet valves. Do I just open these
valves while the system is running to bleed off the air? Ok, I'm
actualy asking after the fact. I already tried doing this but the
flow was very slow, at times it stopped completely. I assumed this was
because the air was beng purged but I held a bucket there for a few
minutes and the flow never increased. Did I not wait long enough or
am I doing this wrong? If there was no air in the system I expect I'd
see a pretty good flow out of that valve, right?

Thanks