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purging air from heating system

I have a baseboard heating system, with some radiant heat zones. I am trying to purge the air out of the system, because one zone is not heating. The thermostat is on, the zone is on of the TACO switch relay, the circulator pump was hot, but still no heat at the baseboard itself. I pulled down the shutoff valve to close the circuit and then open the return screw valve, but no water comes out. I tried this on the other zones that are working and still no water comes out, so it's something I'm doing wrong. Now after watching multiple videos on YouTube there is a step to manually open the zone valve... except I don't have any zone valves. I have TACO circulator pumps on each zone and TACO Flo-Chek valves above each pump. But I have no typical zone valves with automatic/manual switch options. I'm assuming the flow check valves are acting as the zone valves, but how do I open them up to allow water to dump out the return spigot?

I've attached pictures and am hoping someone can clear this up for me.

Thanks for any help or clarification. I hope I am referring to the different parts correctly, so please pardon my ignorance.


  • Empire_2
    Empire_2 Member Posts: 2,343
    Where you see the ball valve shut off, the drain cock above is the return where you can close the ball then open the drain cock to "purge" that particular zone of any air if required. The Q; I have is what is the pressure on the system right now? You should have somewhere about 10 to 12 psi. The angle mechanism you see near the pumps are flo-checks which prevent flow in zones that are not calling. Basically a check but not the same.

    Mike T.
  • icesailor
    icesailor Member Posts: 7,265
    edited January 2015
    I sure hope that you have water in that boiler and the Taco 007 isn't running without water.

    Or, why it really sucks to fill boilers that way because it is so easy to not be able to purge through the boiler and have the boiler being fed through the system and not the fill valve feeding the boiler.

    If that boiler has been running, and you haven't been able to get any water out of the purge valves, shut the boiler off for a few hours. Let it cool down first. Then, be sure that BOTH red handled valves on either side of the Backflow/Pressure reducing Valve are open.

    You really could have a dilemma on your hands.

    When a boiler does the "Phase Dance", there's no time to run away.
  • hot_rod
    hot_rod Member Posts: 18,254
    Has it been working this season? There are some systems that freeze this time of the year if they are turned off for long periods, or the t-stats turned back at night.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • unclejohn
    unclejohn Member Posts: 1,778
    How long is the blue hose you have connected to the purge valve? How long did you wait for the air or water to flow out?Also you need to watch the pressure on the boiler. First shut off all pumps and boiler. Then raise the pressure to around 25 psig. put the hose in a bucket and close the valve below the purge valve like you have done in the picture and let the water run until no bubbles appear in the bucket, may take twenty mins or more.
  • icesailor
    icesailor Member Posts: 7,265
    "" Also you need to watch the pressure on the boiler. First shut off all pumps and boiler. Then raise the pressure to around 25 psig. put the hose in a bucket and close the valve below the purge valve like you have done in the picture and let the water run until no bubbles appear in the bucket, ""

    If you fill the system through a fitting on a connection where the compression tank connects to the supply side, Do that.

    If you fill the system THROUGH the boiler, leave the boiler running so it is hot. You need a properly working Pressure reducing/By-Pass Valve with the by-pass lever open, the water running into the system, and the pressure high. A 6' of longer washing machine works fine into a 5 gallon bucket. With the by-pass valve closed, when you open the drain, the hose should slightly rise out of the bucket from the flowing water. As the water with the air gets closer to the bucket, the nose will noticeably raise out of the bucket. Be aware that the hose might blow out of the bucket when the air and water come. Have your hand on the return line above the hose. You will feel the different temperatures as they go by. There can be times when the water gets very cold. Once the major amount of air bubbles come through, you should feel the water getting warmer or hot. Shut off the drain into the bucket and open the by-pass. Because the boiler is running, the circulator is running too. Once you open the by-pass valve is opened, you should feel the return get extremely hot. Close the by-pass and do the next zone the same way. If at any time the pressure is getting too high, close the bypass lever on the fill valve. If the pressure gets too low to purge, stop the drain. It usually takes way less than 5 minutes to adequately purge a zone. When done, leave the pressure at 20# to 25#. It will settle out.

    You need the higher pressure to compress any remaining air so that the existing pump(s) have the ability to overcome the bouncy of any air left in the system and for the water to absorb the air.

    "" may take twenty mins or more. ""

    Maybe a 4 zone system on a slow day. Not this way. If you have a system that fills through the supply (like everyone wants to do), you never get any hot water and you have no way of knowing when you have purged all the air. Connect a cold water outlet to the bottom boiler drain and fill through the bottom of the boiler. That way, you can have the coiler and circulators running. And the boiler can not overheat because of the water being heated while running through it,
  • swsquash
    swsquash Member Posts: 2
    Ok, so after all that... turns out I had a frozen pipe. That's why I wasn't getting any water return on that one zone. I had set my thermostat to a schedule to drop the temperature at night to save on heating costs. We had one below freezing night a few days before this problem. It was enough to freeze one pipe to that one zone. The other zones were giving a water return after I double checked them (I fooled myself with those quick release valves I had put on to make this process easier, but without a hose attached the quick release valve you get no water flow). So, just that one zone/pipe wasn't returning water and that one zone was on a schedule. Once the pipe thawed, I got return of water and then the heat resumed. Thank you all for your advice and input, always educational.
  • icesailor
    icesailor Member Posts: 7,265
    Don't turn down the thermostats when the temperature goes down way below freezing. That's when you turn it up.

    If you insist on turning thermostats down, turn down the High Limit on the boiler so you pump colder water. Water only freezes if it isn't flowing.

    It is very dangerous to walk out on river ice. There is flowing warmer water under the ice. Don't walk around bird holes. You can fall in.