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Unable to purge air from hydronic baseboard heating system

KC Member Posts: 1
Recently, my Taco 007 went on me. I have a Weil McLain gas fired hydronic baseboard system. Unfortunately, whoever installed this system, did it on the cheap. There are no isolation valves at the circulator or bleeder vents at the baseboards. I have sucessfully purged air from the system before, but this time, I am having no luck. I had to drain the system to replace the circulator. Once repaced, I filled the system with the fast fill on the automatic feed. Then I attached a hose to the drain before the circulator and let it purge at about 25 PSI. The system is still full of air. The house is heating, but I can hear the water cascading through the piping. I am selling the house in a week and need to resolve this issue before then. Should I install a valve between the drain on the return line and the circulator? Is there something I am doing wrong? Any help is greatly appreciated.




  • icesailor
    icesailor Member Posts: 7,265
    Purging Green:

    That green thing above the circulator with the boiler drain above it is an isolation valve. It should have a screw head sticking through it somewhere. The slot should be in the parallel position to the pipe. You need to turn it 90 degrees so it is perpendicular to the flow. Then, purge the system through the drain valve/boiler drain. If you have zone valves, you need to close them all and only open the zone you want to purge. Purge until the water comes back hot. Do all the zones.

    The contractor did not "do it on the cheap" in that situation. "I" would have done it on the cheap by using a standard flange and a ball valve above the circulator. If you did not close the isolation valve, you were only draining water from the boiler and not the system.

    If the cold water fill enters through the supply system, all bets are off as far as the purged system coming back.

    An advantage of feeding HW boilers through the bottom of boilers. You always know if the boiler is vented and the system also.  JMO
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