How to purge air from water heater

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Old 12-07-12, 09:27 PM
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How to purge air from water heater

Hello, i have a lot of air in the the system. Pipe banging so loud at night, i have done some research on the forum. Just want to make sure what i was doing is the correct way. Btw its 3 zones 3 story, cold air pressure filled 18 hot 22 at 180F. As i understand, when purging air from system, must bring the thermostat on high to keep system running, shut off all three zone isolation valves, put fast water feeder on vertical and open zone drain valve one at the time and until no water bubble. Please verify, thanks in advance.
 
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Last edited by hollowplayer; 12-07-12 at 09:54 PM.
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Old 12-07-12, 09:51 PM
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I would say change that air vent on the top of the air separator.

Check and adjust psi in exp tank while you at it.

No need to purge if water is moving. Air vent most likely cause.

Banging may be just thermal expansion, although high temps often cause that, Possibly yours gauge is off and you are exceeding 180f.

Read stickys for exp tank adjust and to verify your pressure gauge.
 
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Old 12-07-12, 09:58 PM
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thanks, i meant the auto air purging tip is one turn loosed as stated in the instruction manual. System is one year old. Loud noise only comes when heat is on, please advise.
 
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Old 12-07-12, 10:30 PM
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i meant the auto air purging tip is one turn loosed


Turned it loose but it may not work...

What type of noise? Banging, or the sound of water running through pipes?
 
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Old 12-07-12, 10:40 PM
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very loud banging sound below one of radiator, water running sound come and go. Is my method correct? Should i shut off only one of zone isolation valve that needed to be drained instead of shut off all three zone isolation valves. Also how long should i leave the water draining. I tested the air auto vent tip according to manual, only a little air comes out when i tap that that tip. I have measured the pressure of that tank, its 12psi as on the label that its factory prefilled. I am afraid that pipe might go busted one day.
 
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Old 12-07-12, 10:49 PM
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Trying to purge air out will only add more air to the system. Your auto air vent is probably faulty.

Plus the boiler may be running too hot. You need to verify your gauge. Read the stickys.

You can drain and purge as you like but it aint going to fix it.....

We are here to help. Take more pics of your system. What type of heat emitters? Cast? Copper?
 
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Old 12-07-12, 10:55 PM
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Will do, thanks! Only radiator making noise is iron cast on the second floor, others on the attic are baseboard cooper dont make any noise.
 
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Old 12-07-12, 11:02 PM
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So you have mixed emitters cast iron and copper? Only one rad makes noise? Or all second floor?
 
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Old 12-07-12, 11:10 PM
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Yeah, only one radiator on second floor making loud bang whenever heat is on, other ones rarely make loud bang maybe once a week or so. When i bleed the system, banging noise might quiet down alittle. All cooper baseboard radiators in attic dont make any noise. Also, i just measured the boiler pressure its same as on the gauge. And the zone valve controller is Honeywell, could it be the culprit? I guess it will replace the air auto vent tip see if banging sound go away. Also how to find out if thermo gauge is off, i have safety set at 210f but boiler shut off at 180f.
 

Last edited by hollowplayer; 12-07-12 at 11:34 PM.
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Old 12-08-12, 10:49 AM
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As i understand, when purging air from system,

must bring the thermostat on high to keep system running,
NO. Turn OFF the system and allow to cool to 100F or less. If you have a HOT boiler and introduce massive amounts of cold water you could crack it... not to mention the hazard of being burned by very hot water.

shut off all three zone isolation valves,
Yes.

put fast water feeder on vertical and open zone drain valve one at the time and until no water bubble
Yes, but watch your pressure gauge as you do so and regulate the amount of water pressure in the system. Don't let it go over say 25 PSI or so.

Also as Mike stated, don't do the purge unless you have absolutely no other choice. Introducing fresh water into the system also introduces all the dissolved air in the water. As soon as that water is heated, that air will come out and form bubbles again in the system. It is far better to allow the air vent on the scoop to do it's job.

=====================

For reference, the stickys that Mike suggested you read are here:

http://www.doityourself.com/forum/bo...sion-tank.html

There is a step by step procedure in that thread explaining the proper procedure to use when checking your expansion tank. In your case since you are in a 3 story home, you need to put a little bit more air in the tank to MATCH your cold fill pressure.

I have measured the pressure of that tank, its 12psi as on the label that its factory prefilled.
So your 12 PSI pressure is a bit on the low side. These need to be recharged in general at LEAST every two years. As stated in the sticky, you can NOT check the air charge in the tank accurately if there is any pressure on the system water side. A normally functioning tank will lose 1-2 PSI per year. (just like a car tire)

http://www.doityourself.com/forum/bo...ure-gauge.html

If your system is only a year old, the gauge may still be OK... I think you said you verified it?

======================

Also how to find out if thermo gauge is off, i have safety set at 210f but boiler shut off at 180f.
The 'safety' you are talking about is the upright rectangular with the pushbutton reset on the front? Yes, 210 is probably OK for that one as it is a SECONDARY or AUXILIARY HIGH LIMIT safety control. This control will stop the boiler firing in the event that the PRIMARY operating control in the aquastat fails to shut off the burner when it should. If the boiler shuts off at 180, that is correct.

I tested the air auto vent tip according to manual, only a little air comes out when i tap that that tip.
Only a year old... and seems to pass the tap of the tip, and no dripping continuously afterward, it is probably OK.

I personally wouldn't change it... it's function is to remove air from the system, but if the air is not being moved down to the air scoop for collection and removal, and stays up in the zones, then it can't do it's job anyway.

======================

I can also see that you have a 'Guard Dog RB 24' LOW WATER CUT OFF installed. That's the round think on the pipe below the auxiliary high limit control. It will shut the boiler down if it goes low on water for any reason.

======================

I tend to think that you may be hearing expansion noises rather than air in the pipes. BANGING is not specifically related to air issues. The water rushing noises ARE related to air though...
 
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Old 12-08-12, 11:19 AM
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Thank you so much for the thoroughly explanation. By the way, how much pressure should i add in to the expansion tank. I followed the steps on top of forum and reading is 12psi and cold filled boiler pressure i added to 18PSI. Should i also add 5psi more to the expansion tank? Thanks again really appreciate your help.
 
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Old 12-08-12, 12:13 PM
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Yes, you should add a few pounds to the expansion tank.

It's pressure should MATCH YOUR COLD FILL BOILER PRESSURE.
 
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Old 12-08-12, 06:37 PM
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Pipe still banging, sigh!! could it be the temperature limit is too high? I browse other threads that normally people set it at 160F. By the way, how to change the system temperature limit to 160F.
 
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Old 12-08-12, 06:58 PM
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could it be the temperature limit is too high? I browse other threads that normally people set it at 160F. By the way, how to change the system temperature limit to 160F.
While it is possible to run the high limit at 160, I highly doubt it will completely solve your problem, and you may end up with not enough heat when the weather gets very cold out.

What is the make and model of your boiler?

Describe the 'banging' issue from only ONE radiator more thoroughly please.

I believe that what you may be hearing is the pipes expanding. The remedy for this is NOT anything at the boiler. It is NOT a problem with the boiler if it is expanding pipes.

Does the banging continue the ENTIRE TIME that the system is heating?

OR, does it occur at the beginning of the cycle and then stop part way through?

Is it only ONE or TWO bangs as the system heats up?

OR, is it a series of bangs, faster at first, and then slowing down?

Like this:

BANG!.... BANG!........BANG!.....................BANG!.............................................bang............etc

Is the banging loud enough to wake someone from a deep sleep?
 
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Old 12-08-12, 07:11 PM
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The model is Williamson GWA gas-fired water boiler. Banging is horrendous, its loud enough to wake up first floor tenants. When system heats up it gives out one loud bang, and then maybe a few mins later another loud one, and when heat reaches 180F it gives out a another loud bang. Pipe expanding should sound like click click click with rhythm is that correct? Appreciate your help.
 

Last edited by hollowplayer; 12-08-12 at 07:35 PM.
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Old 12-08-12, 07:29 PM
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The temperature limit is inside of the cover, i changed high limit to 170F. Is that enough? Banging noise seems to quiet down a few decibel. Maybe the front radiator is in the coldest area of the house and 180F water causing the bang when meeting with colder water?
 
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Old 12-08-12, 07:47 PM
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When system heats up it gives out one loud bang, and then maybe a few mins later another loud one, then when heat reaches 180F it gives out a another loud bang.
This sounds like expansion to me...

I actually had one like that in this house when I moved in many years ago. I ended up having to take up some floor boards to fix it, which I did by slipping some plastic shims cut from an iced tea bottle between the pipe and the hole in the framing.

Maybe the front radiator is far in front of house
The longer the pipe, the more it will expand... so being farthest from the boiler means that there will be more expansion... and yes, if it cools more between cycles it will bang every time it heats up.

Pipe expanding should sound like click click click with rhythm is that correct? Appreciate your help.
Yes, it can sound like that.

In worst cases though, it can sound exactly as you describe, I liken this to an EARTHQUAKE.

You know in an earthquake the pressure builds slowly on a fault line until all of a sudden... KABOOM! The pressure overcomes the friction and there is an earthquake.

Imagine a pipe in the house passing through wooden framing. Perhaps at one point there is friction, maybe the hole is too small. As the pipe expands, and grows LENGTHWISE, the pressure will build up because the pipe is being held by friction against the wood framing.

As the pipe continues to grow lengthwise, at some point it will overcome the friction and JUMP! and create a tremendous noise that will shake the whole frame of the house.

This is not a fault of the boiler.

It is true that lowering the temperature slightly at the boiler will help a little bit. But don't go crazy lowering the temperature because as I mentioned at some point during the winter the water may not be hot enough to heat the home.

Another problem with lowering the temperature has to do with FLUE GAS CONDENSATION where the water in the flue gases are now condensing inside the boiler and the chimney. This condensation is ACIDIC and will ROT OUT the metal of the boiler, the flue pipes, and the masonry in the chimney...

Unfortunately, the fix for your problem is not easy. Somehow you need to find the place where the pipe is passing through an area where it has friction. I'm betting it is INSIDE THE WALL OR FLOOR... you would need to find where it is binding and correct that situation.

Can you localize the sound? Do you have an idea exactly where the banging is coming from?
 
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Old 12-08-12, 07:57 PM
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Can you take pictures of the radiator that is banging? Particularly where the pipes come up through the floor.
 
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Old 12-08-12, 07:59 PM
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Thank you so much NJ Trooper you are the best. Yes its sound exactly like the what you described. Sound comes from right side of the radiator, i think i am gonna call constructor see if they could remap the pipe. 170F is helping tremendously, it doesnt make any loud bang anymore only a few dull clanking sound. Maybe 180F is too much, i will try 175F tomorrow if banging will come back and report back here. Also no more water flowing sound after raised the pressure of the expansion tank. Thanks again, your the best!
 
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Old 12-08-12, 08:02 PM
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If it's right under the radiator it might just be where the pipe comes through the floor! Let's hope so because then you may not have to pay someone...

Take a couple pics, let us see it.
 
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Old 12-08-12, 08:06 PM
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Pic attached, sound comes from right ride of that radiator, is that return pipe? That pipe going through sort of foundation metal thing, could be that 180F causing too much expansion and hitting that metal frame foundation and causing the loud bang.
 
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Old 12-08-12, 08:43 PM
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Pics didn't work.....................
 
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Old 12-09-12, 01:15 AM
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Here is attachment, system has been running for 5 hrs only very dull quiet banging noise when heat came on.
 
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Old 12-09-12, 09:27 AM
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Connecting pipes are not visible... wanted to see where pipes pass through floor or wall...

That is some purty woodwork!
 
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Old 12-09-12, 05:39 PM
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All pipes are hiding in the wall, i think 170F has fixed the problem, only a few quiet cranking noise now. Thank you so much, really appreciate your guides!
 
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Old 12-10-12, 04:53 PM
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I noticed that all three zone valves are in auto position, since i have only one thermostat controlling basement, 2nd fl and attic should i flip it over to hold open? Zone valve is made by Honeywell, maybe its closing too fast to cause the banging?
 
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Old 12-10-12, 05:19 PM
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all three zone valves are in auto position, since i have only one thermostat controlling basement, 2nd fl and attic should i flip it over to hold open?
Well... no, I wouldn't recommend that because you will then have what is called 'gravity flow' where the hot water will 'float' up into the system and push the cold back down and will likely end up with too much heat where you don't need or want it.

What I don't understand is why you have only one thermostat and three zone valves?

Do all three zone valves open when the one thermostat calls for heat?

maybe its closing too fast to cause the banging?
Also called 'water hammer'. I don't think that's the problem here. It would be a different sound and you would only hear it once when a zone valve closed. It is usually a 'metallic' sound, followed quickly by what could sound like an 'echo'. like

CLANK!....clank!
 
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Old 12-10-12, 05:27 PM
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I see, previous owner probably rented out the basement and wanted to control the heat. Yeah when heat is on all zone valves open. Also when i bleed the system, I noticed that 2nd FL has faster pace of flowing water than attic and basement, is there anyway that i can slow it down. Other two zone valve controllers looks brand new, 2nd FL covered with dust and oil residual.
 
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