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Discussion Starter · #1 ·
One zone has been acting up a lot with gurgling noises. I have tried to purge the lines twice now and the noise never goes away, even though no air bubbles eventually come out of the hose. Just to make sure I am doing the purge correctly, these are my steps:

1. Turn boiler off
2. Shutoff all zones besides the one I am purging.
3. Attach hose to return drain valve
4. Manually open zone's valve, open drain valve and maintain pressure with auto fill valve. Continue to run until air is out.

I also noticed that my Taco HiVent valve was dripping water for about 2-3 mins after I purged and started all the zones back up. It is just two years old. Has it failed or is it normal for some water to come out when starting the boiler back up like that? I wonder if that is the reason the remaining air isn't escaping from the system. Thanks for any help on this!
 

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Incoming water can contain dissolved air. Do you have an air purger in the system? Can you find the high point in the loop and put on a connection to bleed off air?
 

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One zone has been acting up a lot with gurgling noises. I have tried to purge the lines twice now and the noise never goes away, even though no air bubbles eventually come out of the hose. Just to make sure I am doing the purge correctly, these are my steps:

1. Turn boiler off
2. Shutoff all zones besides the one I am purging.
3. Attach hose to return drain valve
4. Manually open zone's valve, open drain valve and maintain pressure with auto fill valve. Continue to run until air is out.

I also noticed that my Taco HiVent valve was dripping water for about 2-3 mins after I purged and started all the zones back up. It is just two years old. Has it failed or is it normal for some water to come out when starting the boiler back up like that? I wonder if that is the reason the remaining air isn't escaping from the system. Thanks for any help on this!
Should be an isolation valve between drain valve and boiler that needs to be closed to purge air.
 

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Discussion Starter · #4 ·
I don't have bleeders since it isn't a steam system. The drain valve is installed after the isolation valves for each zone, which I know it isn't ideal. It is a 20+ year old system though. I purged again and the air seems to be out of the system, but that Hi Vent still leaked for a minute or two. Is the vent already shot after 2 years or is this normal after purging?
 

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Some vents will do that. Doesn’t take much dirt to block one open for a minute or so after purging.

Not seeing where the water fill is connected, it doesn’t look like it can be properly purged.
 

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Okay, are you closing the valve on the return pipe just below the auto water feed. And then connecting your garden hose to the drain valve in the first pic, and closing the supply valves to the two zones your not purging.
 

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Shouldn't really have air in the boiler, with the exception of a very small amount that has been returning to the boiler during some heat calls.


Most of the air that gets to the boiler, will rise and leave the system through the air vent.
 

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My experience with high vents is they generally fail after 2-4 years. I finally gave up and eliminated all of them in my system. I plugged them with a small valve I can open manually if needed, but so far purging using the OP's method works fine.

I also have an air scoop above the expansion tank. I didn't see that in the pictures above. That's the only high vent I have now. It's easy to see when it's leaking, and easy to replace. I always have a spare handy.
 

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I had a similar problem and even after purging the system found it still gurgled somewhat albeit not as bad as before purging.

I have since discovered that after purging the system, it helps to open the auto-fill valve allowing water to flow for about 5 seconds or so. I cannot say why this works only that it does.
 

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Discussion Starter · #15 ·
So I have purged as was suggested. This worked for a few days and now that zone has a constant water running sound when I turn it on. What could be causing this to be coming back after a few days? Should I try to replace the Hy-Vent?
 

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Air is being drawn in by one of the vents, or you have a leak in the system.


Try vent replacement first.
 

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Discussion Starter · #17 ·
I finally got some free time after the holidays to mess with the boiler. I purged the system and got a lot of big bubbles out of the highest zone, which is the zone that has been causing me issues. I purged until no more bubbles and then turned the boiler on for that zone. Water seemed to rush through the pipes to sounded as if they were filling. After that initial 1 or 2 mins of noise, the gurgling has gone away. Instead though, you still hear bubbles moving through but it is much quieter. My other zones I hear nothing though.

Here is the process I tried when purging:

1. I closed the valve between the boiler and water feed. Then I attached the hose to the drain in the original photo.
2. When that didn't work, I tried to connect the hose to the drain that is before the electrical valves for each zone because I saw a boiler guy purge from there in the past. That gave me more air bubbles while purging, but didn't cure the system completely.

Both times I tried to force bubbles out by manually feeding water since I have heard others suggest this. I also would hear air being released through the hy-vent once I turned the system back on both times.

My questions are:
1. Should I run the boiler while purging? Are there any other tactics I should be trying?
2. I replaced my hy-vent because it was continuously leaking. If there is a leak in the system, where would this be coming from?
3. Is the issue that I don't have a proper drain valve before the ball valve I the system?

We are struggling here and two different boiler guys haven't been able to help. Any more suggestions would be great! Thank you!
 

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Did you manually open the zone valve when yo had the hose connected to the valve in the first Pic.
 

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My questions are:
1. Should I run the boiler while purging? Are there any other tactics I should be trying?
2. I replaced my hy-vent because it was continuously leaking. If there is a leak in the system, where would this be coming from?
3. Is the issue that I don't have a proper drain valve before the ball valve I the system?
I'm no expert. Hopefully if I'm wrong, someone will correct me. But I'll give it my best shot:

1. I've heard tales of hot boilers cracking when a lot of cold water is suddenly introduced. I do know that cast iron is brittle. I generally shut off the boiler and wait a bit so it's not at its maximum temperature when I purge. I don't wait for it to fully cool off, but probably would let it get quite a bit cooler if I was planning to dump in a lot of water, especially in winter when the incoming water is just above freezing.

2. I can only guess. Any joint with a slow leak can suck a little air when the loop cools. But if the leak is so small you can't see or hear it, I'd guess there wouldn't be much air, and your high vents could handle it. Generally you can find a leak in the living space by the smell. If it's inside a wall, you might not notice until the wood starts to soften and rot or sheetrock gets stained.

3. If you can get a good flow of water through the system, you should be good.

I'm not convinced you haven't fixed it already. When you introduce a lot of fresh water, it takes a while for all the air to work its way out. If you can hear the high vents releasing, it should get less frequent over time.
 
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