Air in hot boiler lines - even after they have been purged
#1
02-02-11, 04:59 PM
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Running water sound in hot water boiler lines - even after they have been purged
Ok I need a little help here. I've recently heard the sound of running water in one of my heating zones. I figured that there had to be some air in the line so I purged it SEVERAL times. I still hear the running water sound. Here is a brief description of my system and how I purged the system.
I'll start at the water supply. My water comes from the street side and goes into my automatic fill valve, from here the pipe connects a T-joint. The right side of the T is where my expansion tank is located (gray propane tank looking tank). On top of the tank is an air seperator. After the water passes through the expansion tank it goes to my zone pumps. I have 3 zone pumps. The first pump is my 2nd floor, next is my main floor and the third pump is my basement zone. I have all zone pumps set to medium. There are shut off valves on either side of each zone pump. After the water circulates through each zone they all return at the same spot where I have a drain spigot, then the line goes into my main circulating pump, again shut off vales are on either side of this pump. From here the water enters the boiler to be reheated and then exits, this is the pipe that connects to the left side of the T where the fill valve comes in.
The procedure that I have been doing. After the boiler has been shut down and the drain hose has been connected to the drain spigot I close the shutoff valve near the main circulating pump to prevent cold water from entering my boiler. Next I close the valves to main floor and basement zones. I then open my drain spigot and lift the handle on the fill valve so I get street pressure water running through my 2nd floor zone. Once all the drain water has stopped bubbling, I close my 2nd floor valve and open the main floor zone. The same process is followed for the basement zone. Once all air has been expelled, I close the fill valve so I'm only getting 12 lbs of pressure again. When the pressure gauge falls to 12 PSI, I close the drain spigot and open all valves to my 3 zones and my main circulating pump and restart the boiler. Everything seems fine for a few days, and then I start to hear running water again.
I only hear the running water sound in my second floor zone. All the piping to this zone is 3/4 pex. The other 2 zones are 3/4 copper. I've started to think that maybe I have a leak in the pex tubing somewhere but I have looked everywhere and there are no wet spots. Any suggestions?
I'll start at the water supply. My water comes from the street side and goes into my automatic fill valve, from here the pipe connects a T-joint. The right side of the T is where my expansion tank is located (gray propane tank looking tank). On top of the tank is an air seperator. After the water passes through the expansion tank it goes to my zone pumps. I have 3 zone pumps. The first pump is my 2nd floor, next is my main floor and the third pump is my basement zone. I have all zone pumps set to medium. There are shut off valves on either side of each zone pump. After the water circulates through each zone they all return at the same spot where I have a drain spigot, then the line goes into my main circulating pump, again shut off vales are on either side of this pump. From here the water enters the boiler to be reheated and then exits, this is the pipe that connects to the left side of the T where the fill valve comes in.
The procedure that I have been doing. After the boiler has been shut down and the drain hose has been connected to the drain spigot I close the shutoff valve near the main circulating pump to prevent cold water from entering my boiler. Next I close the valves to main floor and basement zones. I then open my drain spigot and lift the handle on the fill valve so I get street pressure water running through my 2nd floor zone. Once all the drain water has stopped bubbling, I close my 2nd floor valve and open the main floor zone. The same process is followed for the basement zone. Once all air has been expelled, I close the fill valve so I'm only getting 12 lbs of pressure again. When the pressure gauge falls to 12 PSI, I close the drain spigot and open all valves to my 3 zones and my main circulating pump and restart the boiler. Everything seems fine for a few days, and then I start to hear running water again.
I only hear the running water sound in my second floor zone. All the piping to this zone is 3/4 pex. The other 2 zones are 3/4 copper. I've started to think that maybe I have a leak in the pex tubing somewhere but I have looked everywhere and there are no wet spots. Any suggestions?
#2
02-02-11, 05:23 PM
All your symptoms point to not enough pressure in the boiler, in spite of what the gauge says. If you read any of my posts here, you know that if someone mentions a pressure gauge, I go off...
Never trust a boiler pressure gauge! (my personal mantra).
So, I would suggest that the first thing to do is get to a known starting point with a verified known good pressure gauge.
When you run the boiler and it gets HOT, what does the gauge read then?
Does the gauge ever read BELOW 12 PSI?
Never trust a boiler pressure gauge! (my personal mantra).
So, I would suggest that the first thing to do is get to a known starting point with a verified known good pressure gauge.
When you run the boiler and it gets HOT, what does the gauge read then?
Does the gauge ever read BELOW 12 PSI?
#3
02-02-11, 05:37 PM
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In additon to what Trooper said about the pressure let me add my two cents.
All of that fresh water your are adding contains oxygen (BAD, BAD, BAD, in case I forgot to say so, that's bad). Cold water will hold far more dissolved gasses than will hot water. As the water heats, all of those dissolved gasses come out of solution, thus bubbles. Not to mention all of the damage all of that fresh water can do to your system.
Is your PEX loop done with PEX with an oxygen barrier? If not, you can actually be pulling in air thru the walls of the PEX.
All of that fresh water your are adding contains oxygen (BAD, BAD, BAD, in case I forgot to say so, that's bad). Cold water will hold far more dissolved gasses than will hot water. As the water heats, all of those dissolved gasses come out of solution, thus bubbles. Not to mention all of the damage all of that fresh water can do to your system.
Is your PEX loop done with PEX with an oxygen barrier? If not, you can actually be pulling in air thru the walls of the PEX.
#4
02-02-11, 05:47 PM
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I have never seen my guage fall below 12 PSI. I believe that I am running at the correct pressure because as the water is draining out the drain valve I shut it off just as the auto fill valve starts to turn on. Now my fill valve is set for 12PSI so that should keep a constant 12 PSI correct? FYI - I recently replaced this fill valve because I too was thinking that the old one was malfunctioning.
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02-02-11, 05:50 PM
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I do have oxygen barrier pex. I understand your comments on using the cold water, now let me add this. In order to combat this, I have also tried using the water from my hot water tank to purge my boiler system. Same results. Goog for a few days and then the running water sounds returns.
#6
02-02-11, 06:03 PM
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Are all you air vents working. You cant get all the air out. The air vents take care of the rest. You could be sucking air in also. Do you have air vents on the basement loop?
Mike NJ
Mike NJ
#7
02-02-11, 06:11 PM
When you run the boiler and it gets HOT, what does the gauge read then?
By the way... if you DO have a small leak somewhere, that HOT water will evaporate on the HOT pipes so quickly that you may never see a 'wet spot'. Instead, look for mineral encrusted pipe joints and valves.
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02-02-11, 06:20 PM
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Yes, the valve was preset to12psi. The guage now actually reads 14psi after the valve was installed. I have a 30psi pressure relief valve and that releases at 32psi now instead of 30psi. When the boiler is hot and running, my pressure increases to about 16psi. I have never seen it above that.
#11
02-02-11, 06:26 PM
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I have a Dunkirk 4 burner boiler. About 3 years ago I put an addition on the house (the 2nd floor) thus the PEX. Prior to this addition I had 2 zone valves, not pumps. After I built the addition, the HVAC guys removed the valves and installed zone pumps but they never eliminated the old circulator, that I'm calling the main circulator. The only piping scheme that I am running is how I explained it to you. I'll get some pictures for you.
#12
02-02-11, 06:36 PM
OK, so you know that the 'main pump' is totally useless then, and should be removed... but not part of your current problem.
So you think that the gauge is reading about 2 PSI high, then that 16 PSI you see is really 14 PSI I think, correct?
You say you never see the gauge above 16, but you did say that the relief opens at 32, so at least ONCE you saw it above 16 then? You mean when the boiler is running NORMALLY, you don't see it over 16, correct?
Is that 16 that you see when the boiler temp is up at 180 ?
What SIZE expansion tank do you have ? i.e. 15, 30, 60 ?
You may know that you can't post pics here directly. They have to go to a photo hosting site and be 'linked' in... set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload the pics there... come back here and drop a link to your public album for us to view.
The easiest way to check if your system is holding pressure would be to let it cool, set the pressure at 12 PSI , then CLOSE THE MANUAL water feed valve for a day-two-three and monitor the pressure. If it starts dropping, look for a leak.
So you think that the gauge is reading about 2 PSI high, then that 16 PSI you see is really 14 PSI I think, correct?
You say you never see the gauge above 16, but you did say that the relief opens at 32, so at least ONCE you saw it above 16 then? You mean when the boiler is running NORMALLY, you don't see it over 16, correct?
Is that 16 that you see when the boiler temp is up at 180 ?
What SIZE expansion tank do you have ? i.e. 15, 30, 60 ?
You may know that you can't post pics here directly. They have to go to a photo hosting site and be 'linked' in... set up a free account at Image hosting, free photo sharing & video sharing at Photobucket and upload the pics there... come back here and drop a link to your public album for us to view.
The easiest way to check if your system is holding pressure would be to let it cool, set the pressure at 12 PSI , then CLOSE THE MANUAL water feed valve for a day-two-three and monitor the pressure. If it starts dropping, look for a leak.
#13
02-02-11, 06:55 PM
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Yes, I guess I have seen the guage above 16psi. We tested the pressure relief valve to verify that the new fill valve was set correctly to 12psi and it appeared that it was. Under normal operation, I have never seen it above 16psi. Yes boiler temp right now is 180 degrees with a pressure of 16psi.
Expansion tank is an Extrol, preset to 12psi (max 100psi) not sure 15, 30, or 60 I don't see any other numbers on it.
Above the expansion tank is an Amtrol air seperator. The screw end (looks like a tire valve cap) is about 3/4 the way open. My 3 zone pumps are Grundfos, all set to medium. My boiler is a Dunkirk PVWB-4D.
Thanks for eveybodies help. I will get some pictures and share them in photo bucket.
Expansion tank is an Extrol, preset to 12psi (max 100psi) not sure 15, 30, or 60 I don't see any other numbers on it.
Above the expansion tank is an Amtrol air seperator. The screw end (looks like a tire valve cap) is about 3/4 the way open. My 3 zone pumps are Grundfos, all set to medium. My boiler is a Dunkirk PVWB-4D.
Thanks for eveybodies help. I will get some pictures and share them in photo bucket.
#14
02-02-11, 07:33 PM
I think you are fairly confident in the gauge's accuracy, and you've more or less convince me too...
I guess the best thing would be to do the pressure test... close the feed valve and see what happens.
I'll keep my eye out for the pics.
I guess the best thing would be to do the pressure test... close the feed valve and see what happens.
I'll keep my eye out for the pics.
#15
02-03-11, 05:01 PM
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Ok lastnight I closed the feed valve and the recorded the pressure reading, 16 psi. I also closed the (valve stem looking cap) on the air seperator. I was thinking that maybe it was sucking air for some reason. When I got home today, the pressure has actually risen to 18 psi. (All this was done after I purged all the zones again). Fyi still hear the water rushing sound.
Another observation that I've noticed. As I said before I only hear the sound of rushing water in my 2nd floor zone. It seems to do it immediately after the thermostat calls for heat. Once the pump has turned on you hear the rushing water sound until it has circulated around the zone. Normally, you don't hear it again until the next time the pump turns on.
Here is the link to my photo bucket.
ashilling boiler photos pictures by ashilling44 - Photobucket
Another observation that I've noticed. As I said before I only hear the sound of rushing water in my 2nd floor zone. It seems to do it immediately after the thermostat calls for heat. Once the pump has turned on you hear the rushing water sound until it has circulated around the zone. Normally, you don't hear it again until the next time the pump turns on.
Here is the link to my photo bucket.
ashilling boiler photos pictures by ashilling44 - Photobucket
#16
02-03-11, 06:54 PM
I see nothing in the pics that would account for the air problem you are having. Everything is about as OK as it can be, and you are 'pumping away' from the expansion tank... well, almost.
I really think you should get rid of that 'main pump'. It is doing absolutely nothing to help. I don't think it's actually contributing to your problem, but it's 'uncharted territory' so we can't be sure... I don't see how it could be a factor, but stranger things have happened. The bottom line is that it is absolutely not needed, so why spend the electricity to run it? You could just pick up a pair of flanges, a hunk of pipe, and make a pipe section with the flanges that fits in place of the pump. A little bit ghetto, but if it works, what the hell?
Your purge procedure sounds right also...
Your pressure seems to be hanging tough also, so I don't suspect leaks.
My brainiac keeps going back to not enough pressure...
Let's try two more things.
First, you said all your pumps are set to medium... try setting the second floor to HIGH for a few days and make note of any difference in behavior. If nothing different is noted, return it to medium.
Next, estimate how many feet from the bottom of the boiler to the highest point in the system. Multiply that by 0.432 PSI. Then add 4 PSI. If that number is higher than 12 PSI (tell us what you came up with), let the boiler cool off, and jack the system pressure by lifting the fast fill up to that figure... and run the system for a few days and note the results.
I really think you should get rid of that 'main pump'. It is doing absolutely nothing to help. I don't think it's actually contributing to your problem, but it's 'uncharted territory' so we can't be sure... I don't see how it could be a factor, but stranger things have happened. The bottom line is that it is absolutely not needed, so why spend the electricity to run it? You could just pick up a pair of flanges, a hunk of pipe, and make a pipe section with the flanges that fits in place of the pump. A little bit ghetto, but if it works, what the hell?
Your purge procedure sounds right also...
Your pressure seems to be hanging tough also, so I don't suspect leaks.
My brainiac keeps going back to not enough pressure...
Let's try two more things.
First, you said all your pumps are set to medium... try setting the second floor to HIGH for a few days and make note of any difference in behavior. If nothing different is noted, return it to medium.
Next, estimate how many feet from the bottom of the boiler to the highest point in the system. Multiply that by 0.432 PSI. Then add 4 PSI. If that number is higher than 12 PSI (tell us what you came up with), let the boiler cool off, and jack the system pressure by lifting the fast fill up to that figure... and run the system for a few days and note the results.
#17
02-03-11, 06:58 PM
One other thing... are you sure that the SpiroVent is actually venting? No chance of the air vent being blocked?
And for what it's worth, I'm the ultimate skeptic... I'm still suspicious of the boiler gauge.
And for what it's worth, I'm the ultimate skeptic... I'm still suspicious of the boiler gauge.
#18
02-04-11, 08:46 AM
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I agree about the main circulator being useless. I will eliminate that from the system, not a problem at all considering there are shut off valves on either side.
I have a split level ranch so the estimated measurement per your directions is 13'. 13 x .432 = 5.616 + 4 = 9.616
I'll also try switching the pump speed to high for a few days.
How would I know if the SpiroVent is actually venting? How can I check it? Is there a chance that it could be sucking air in?
Regarding the guage - I fully understand your apprehensiveness. All I can tell you is with my old fill valve It read 12 psi. After I installed the new fill valve (that was preset to 12psi) the guage reads 14psi. I have a 30psi pressure relief valve that know blows off at 32psi. With no other info, it appears to me that guage is 2 psi off. Maybe a coincidence, I don't know.
I appreciate all your help thus far. I'll keep ya posted.
I have a split level ranch so the estimated measurement per your directions is 13'. 13 x .432 = 5.616 + 4 = 9.616
I'll also try switching the pump speed to high for a few days.
How would I know if the SpiroVent is actually venting? How can I check it? Is there a chance that it could be sucking air in?
Regarding the guage - I fully understand your apprehensiveness. All I can tell you is with my old fill valve It read 12 psi. After I installed the new fill valve (that was preset to 12psi) the guage reads 14psi. I have a 30psi pressure relief valve that know blows off at 32psi. With no other info, it appears to me that guage is 2 psi off. Maybe a coincidence, I don't know.
I appreciate all your help thus far. I'll keep ya posted.
#19
02-04-11, 12:14 PM
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Trooper - I was reading some of your other suggestions on other posts. Do you think that my air seperator is not working. Review this thread, http://forum.doityourself.com/boiler...ir-system.html it sounds similiar to the problem that I am experiencing. I can purge the air everyday, but as Grady stated earlier, if I continually add cold water it is going to keep releasing air into the system as it heats up, thus the rushing water noise will never go away. Under normal condidtions, the air seperator should take care of the air that is released after it's heated up correct.
FYI - I am going to replace my pressure gauge. Better to be safe right?
FYI - I am going to replace my pressure gauge. Better to be safe right?
Last edited by NJT; 02-04-11 at 03:23 PM.
#20
02-04-11, 03:39 PM
Ohhh... split level... I was thinking you mighta had one of them tall old victorians with 10' ceilings... in which case 12 PSI would have been 'marginal' ... but what you've got, 12 cold should be perfectly fine.
Yes, correct... fresh water has lots of dissolved O2 in it and it will come out of the water when heated... but that's where the SpiroVent takes over and is supposed to catch and release the air.
If you are actually moving the air from the zone (i.e. it's not getting 'air locked' with no flow in the loop because of trapped air) that air should be caught and expelled by the SV... why that isn't happening? It's difficult for me to believe that it's got a blockage... I dunno!
You DO leave the vent cap loose, right?
If you want to go ahead and replace the gauge that's fine, but there is a way to verify without doing that. Might cost ya like $20 or so... at the top of the forum message list, click on the box that says 'search forum'. Search on the words 'verify pressure gauge' and start reading through the posts that pop up... you should find one that tells you how to make an adapter with a gauge that screws onto any boiler drain. I use a homemade one that looks like this:
Under normal condidtions, the air seperator should take care of the air that is released after it's heated up correct.
If you are actually moving the air from the zone (i.e. it's not getting 'air locked' with no flow in the loop because of trapped air) that air should be caught and expelled by the SV... why that isn't happening? It's difficult for me to believe that it's got a blockage... I dunno!
You DO leave the vent cap loose, right?
If you want to go ahead and replace the gauge that's fine, but there is a way to verify without doing that. Might cost ya like $20 or so... at the top of the forum message list, click on the box that says 'search forum'. Search on the words 'verify pressure gauge' and start reading through the posts that pop up... you should find one that tells you how to make an adapter with a gauge that screws onto any boiler drain. I use a homemade one that looks like this:
#21
02-04-11, 04:05 PM
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In theory the air separator should remove the air after a while but with all the traps in the piping, any venting system is going to have a tough job ahead of it.
Do you ever hear air coming from the vent? If not the SpiroVent could have a problem. This tells you how to clean it: http://www.spirotherm.com/docs/installation/JrIOM-A.pdf
Do you ever hear air coming from the vent? If not the SpiroVent could have a problem. This tells you how to clean it: http://www.spirotherm.com/docs/installation/JrIOM-A.pdf
#22
02-05-11, 11:39 AM
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I can't say that i have ever heard any air being expelled from the vent. I looked at the site you provided and cleaned as stated. There was some black sludge looking stuff inside. When the cap was removed I looked down in the vent body assembly. It looked like there were some brush looking things in there. I can't remove them nor can I reach them to attempt to clean them. I am now in the waiting stage to see what happens. I'll keep you posted.
#23
02-05-11, 11:57 AM
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Trooper I don't believe that I have a blockage. I'm pretty confident about that, I haven't lost an heat in any zone so the water must be circulating, just has makes noise.
Yesterday I was researching the Extrol tanks. I read that it should have been precharged to 12psi. I brought my system down to 0psi, and used a tire guage on the tank, 0psi. I put 12psi of air into the tank and checked it several times then brought my system back up to 12 psi. (New boiler gauage has been installed, reads 12 psi now.) After the boiler was up to 180 degrees I checked the pressure on the Extrol tank, 14psi.
Yesterday I was researching the Extrol tanks. I read that it should have been precharged to 12psi. I brought my system down to 0psi, and used a tire guage on the tank, 0psi. I put 12psi of air into the tank and checked it several times then brought my system back up to 12 psi. (New boiler gauage has been installed, reads 12 psi now.) After the boiler was up to 180 degrees I checked the pressure on the Extrol tank, 14psi.
#24
02-05-11, 12:10 PM
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What used to help when we had a trouble zone is purge the air out like you describe in the first post, but run the circ on that zone. So while the gas is on pilot call for heat on that zone, and purge with the circ running. Do this multiple times. Get the pressure up high around 30psi. A Wiel Mclain engineer that worked for us said keeping higher pressure in the boiler helps compress the air better, or something. And of course change your air vent if not working.
I think once or twice a pony pump was used also to force water into the trouble zone for purging.
Mike NJ
I think once or twice a pony pump was used also to force water into the trouble zone for purging.
Mike NJ
#25
02-05-11, 02:32 PM
I read that it should have been precharged to 12psi. I brought my system down to 0psi, and used a tire guage on the tank, 0psi. I put 12psi of air into the tank and checked it several times then brought my system back up to 12 psi. (New boiler gauage has been installed, reads 12 psi now.) After the boiler was up to 180 degrees I checked the pressure on the Extrol tank, 14psi.
When you saw 14 on the Extrol, did that agree with the boiler gauge? It should have. If the tank is properly charged, a gauge on the air valve will read the GREATER of the two pressures... if there was 12 PSI in the tank with zero on the boiler, you would read 12 PSI until the boiler pressure increased above that point... then you would begin to read the boiler pressure because it would be compressing the air in the tank...
It's also very possible that this has been the problem all along... but it is also VERY surprising to me that you have not said that the relief valve opened up... because with no air in the expansion tank, you should have been having WILD pressure swings when the system heated.
#26
02-06-11, 08:17 AM
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yeswhen I added air to the Extrol I checked the boiler guage as per your directions in that other thread. The boiler guage did go up a little so I drained it again and adjust the air as necessary. I put 12psi in the tank, brought the boiler pressure up to 12psi and fired it all up. Once the boiler temp reached 180 I took pressure readings, 15 on the enxtrol and 14 on the boiler.
After doing this and then cleaning the SV per Grady's instructions, so far so good - no running water noises. I'll keep you posted. I'm not going to touch the system for he next few days to see if they problem is gone. I REALLY hope it is. Thank you much to Trooper and Grady for all your help. You guys ROCK!!!!
After doing this and then cleaning the SV per Grady's instructions, so far so good - no running water noises. I'll keep you posted. I'm not going to touch the system for he next few days to see if they problem is gone. I REALLY hope it is. Thank you much to Trooper and Grady for all your help. You guys ROCK!!!!
