AIr in FHW system

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
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hey george try ask toh.org its ask this old house smitty snipped-for-privacy@msn.com
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Ultimately it depends on the system and how it was hooked up. If the installer planned properly for this, it should be easy.
Your method sounds right but you need to open the zone valve and run the pump or the water will not flow. There may be a manual bypass valve which allows water to circulate in the zone without the pump, activate that if you have it. There may be an electronic solenoid valve in addition to the pump or the pumps may serve that purpose themselves.
You will need a heck of a lot more than a bucket. Attach a garden hose to the faucet valve and run it outside. When you open the valve and turn on the zone pump, lots of water and air pockets will purge out the hose while new water will fill the boiler from its inlet pipe (which should also already be open). Run it long enough to replace all the water in the pipes and observe the outlet hose for a smooth steady stream with no gurgling.
The way you did it, it sounds like you drained an isolated short section of pipe, thereby adding more air to the loop. If you had been purging a large amount of trapped air, it would probably hiss then be followed by lots of water.
In the end, it might be worth the $ to have a heating guy come out and show you how to do it properly once and for all. If you insist on asking us, try posting a few pix (on your own webspace) and put the links here so we know what you actually have. Even the same furnace can be installed a myriad of ways to satisfy particular needs and space.

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