Trapped Air Pocket in Hot Water Heating System

KAH

I have a hot water radiator system (single pipe loop feed with the two venturis for each radiator).  I replaced one of the radiators on the second floor with baseboard.  I did this a number of years ago and I have a bleeder valve on the end of the baseboard closest to the return pipe.  In the past, after draining the system, the return venturi was able to pull the water through the system and back down to the loop feed in the basement (even without using the bleeder). 

I had to drain and refill the system this fall and for some reason the water has not been pulled through the baseboard.  I used the bleeder and I have hot water coming from the feed (just the water that traveled up the pipe when I bled it), but the water is still not being sucked down by the return venturi and is not circulating through the baseboard.  Any suggestions?  Thanks.

Mark Eatherton

Stop the pumps....

You got lucky the last time. I have NEVER been able to force purge a venturi system. It must be bottom filled and top bled, and the pumps must be in the off position.



If you lift the end of the convectors' fin tube element where the coin key vent is located, you MIGHT get the bubble.



Once you'v bled all the free air out, the disolved oxygen should be expelled by the air elimination/recovery system.



ME



ME

KAH

Thanks

OK - I guess I have been lucky..............I'll turn the system off and try letting more water in and see if that breaks the air pocket.....I'll also try tipping the pipe.  Hopefully something will give because my office is getting very cold.

Thanks

Alan (California Radiant) Forbes

Mark Eatherton

once passed on a trick to remove some pesky air from a job I was having trouble with.  Add some liquid dishwashing soap to your system.  Mine was a 2-pipe radiator system and the soap made it too slippery for the air to hold on any more.  I think I had to increase the pressure to 25 psi to make the bubbles smaller, but they finally gave up the ghost.

Mark Eatherton

I was holding that card up my sleeve....

Last time I pulled it out here on the Wall, I caught so much flack, you'd have thought I was promoting the use of magnetic water conditioners or something :-)



Truth be known, it is NOT my original idea. It was taught to me by an old plumber. Wait a minute, I'm an old plumber now....



Thanks for the reminder Alan. ;-0



ME