# Boiler Heater Auto-fill valve & purging



## hurleypatrick9 (Dec 14, 2021)

Hi there.

New homeowner here and novice plumber. I have a boiler with hydronic baseboard radiators. We were getting no heat upstairs (2nd floor) whatsoever, so I took it upon myself to study up and went through the purge process for that zone. Seemed to have done the trick immediately. A few questions arose however, so I want to put it to the forum for help.

1. When I went to switch the auto-fill valve to manual mode so it will flush the system with main line water and push the air out, I found a stop valve just upstream of the auto-fill valve that was closed (blue, pic 1). This surprised me, as I was under the impression that it needs to be open (at least cracked) for the auto-fill valve to do its job. However, this water supply line is split and seems to flow both into one of the circulator returns as well as the bottom of the boiler. The red stop valve was open. Which one should be open and which one should be closed? Does this explain why air got trapped in the second floor baseboards and wasn't automatically pushed through with new water? Could it have done any damage being closed? Any risk keeping them both open with the auto-fill valve on "auto" mode?

2. Some of the zones don't have stop valves (pic 2), so I had to purge the upstairs with the basement zone still open. Could that have potentially pushed air into the basement zone? Any work-arounds for this in the future so I can diligently purge one zone at a time? Could I potentially flush both at once if I can't close the zone and have access to two garden hoses?

3. When I opened the auto-fill valve and it's blue stop valve to purge upstairs, I heard fresh water flush through and watched it push air and old water out of the upstairs zone. (Good!) But, after a minute, the relief valve dumped a fair amount of water out the back of the boiler. Did I open the water main line too far? Is this expected to happen? its a 30 lb relief valve and now the pressure is about 21psi.

4. I don't seem to have any 'zone valves', or at least what I thought were zone valves. Just circulators and zone switches (electrical boxes). I do have some flow check valves (pic 3) - what do these do? Do I ever need to adjust/open/close during the purge process? Am I just not seeing the zone valves?


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## MACPLUMB777 (Jun 18, 2008)

GO TO Heating Help: The Wall, WRONG FORUM THAT YOU ARE NOT QUILITYFIED FOR !


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## skoronesa (Oct 27, 2015)

hurleypatrick9 said:


> Hi there.
> 
> New homeowner here and _*novice plumber*_. I have a boiler with hydronic baseboard radiators. We were getting no heat upstairs (2nd floor) whatsoever, so I took it upon myself to study up and went through the purge process for that zone. Seemed to have done the trick immediately. A few questions arose however, so I want to put it to the forum for help.
> 
> ...


How many hours into your apprenticeship are you? You can't ask your Master these questions?


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## Logtec (Jun 3, 2018)

I’m not reading that much, if you didn’t bother to read the forums..


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