Air in lines, banging noises, pressure questions.

Reply

  #1  
Old 12-18-12, 08:59 AM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Air in lines, banging noises, pressure questions.

Ok, so I have banging noises when the boiler kicks on, then I hear gushing water running thru the pipes. I know I have air in the system. I have bled the lines several times, and I can see the air coming out. I let the zones bleed out for up to a minute after I see no bubbles. A couple of days of quiet, and then back to the same routine. I have 3 zones, each with its own drain valve. I drain them one at a time. Any ideas ?.

The expansion tank was replaced last year, and the tap test tells me it is half water, half air. The bleeder valve on top of the expansion tank was replaced at the same time, and the cap is loose.

The boiler pressure gauge reads around 20 "at rest", and goes up to about 24 when the thing fires up. Is that too high ?. I put it manually to that level based on what the last service guy told me to do. I am reading however, that it should be 12-15 lbs. Could the higher pressure contribute to the banging ?. Boiler is more than 10 years old (was there when I bought the house - it is by no means an ancient system).

Also, am I doing the bleeding incorrectly ?. What I do is = connect hose to zone, open valve, and then open intake valve to increase circulation and push the air out.......should I not open the intake and let the system balance itself.....typically, how long should the water run ?.

Thanks !
 
Sponsored Links
  #2  
Old 12-18-12, 09:18 AM
Member
Join Date: Jan 2012
Location: Canada
Posts: 2,739
Received 16 Votes on 15 Posts
20PSI is fine.
The 12-15PSI is when the water is cold and really is about the minimum.

I'm assuming you have baseboard style rads?
Are there bleed screws at each rad or anywhere along the piping that could be letting air in?
 
  #3  
Old 12-18-12, 09:26 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
the tap test tells me it is half water, half air.
Yeah... well... the 'tap test' is a useless test.

Read the sticky post at the top of the forum titled " Relief valve leaking? ...

There are instructions in there for properly checking and charging the expansion tank.

Could the higher pressure contribute to the banging
No.

Remember that adding fresh water to the system continually is a "Catch 22"... as soon as you heat that fresh water up, all that dissolved air comes out of the new water and you are back where you started.

Can you take many pictures of your system so we can look and see if there are any reasons we might be able to spot for the continued air problem?
 
  #4  
Old 12-18-12, 09:27 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
While you are checking out the sticky posts, read the one about verifying your pressure gauge as well.

Your gauge could be poo.
 
  #5  
Old 12-18-12, 11:00 AM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Only one zone has a bleed screw. We put that in about 7 years ago when we added one radiator. That would be the first floor. The basement and second floor are the other 2 zones and they have no bleed screws (I have searched).

I will read the stickies and post photos.
 
  #6  
Old 12-18-12, 11:30 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
The higher pressure will actually assist in controlling an air problem because the bubbles will be smaller (compressed) and more easily moved through the system.

What I'm hoping to see in the pics is a proper air scoop with an automatic air vent on top.

I do have suspicions about your gauge (don't I always?). If the gauge is reading higher pressure than you really have, it would mean that you may not have enough pressure in the system and this would definitely contribute to a continuing air problem.

I think that verifying the gauge accuracy is the first step. You need to know how much pressure you REALLY have in the system before you can do much else.

One more question: How 'tall' is your home? More than 2 stories? This makes a difference in the minimum pressure allowed.
 
  #7  
Old 12-18-12, 12:56 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
@NJTrooper: My house has 2 levels + basement.

About the gauge = once I let it hit 30 lbs. and the relief valve opened (set for 30), so it is accurate at least at 30......
 
  #8  
Old 12-18-12, 05:35 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Photos

1. The system


2. The zones


3. The gauge (while running)


4. Intake


5. Relief


6. Expansion
 
  #9  
Old 12-19-12, 03:38 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Everything I see appears to be "OK".

You've been in the home 10 years? Is this a new thing that's going on now? Or have you been putting up with the problem all this time?

I'd like you to look over a few articles on the subject of 'pumping away'.

Pumping Away

http://www.fiainc.com/documents/4-09...treallmean.pdf

Let me know if you have any question as to why I'd like you to read these!
 
  #10  
Old 12-19-12, 04:34 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
I've heard the occasional banging, but it seems more frequent now. The water rushing noise is definitely new and way more bothersome. After reading your links......my expansion tank appears to be on the return, and from the looks of it, the circulator is at the beginning of the run, "pushing" water thru the system until it returns back and hits the expansion tank and finally on to the boiler.....or is it the other way around ?

I'm getting cross-eyed now just thinking about this.
 
  #11  
Old 12-19-12, 05:56 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
I'm getting cross-eyed now just thinking about this.
Sorry 'bout that... but "join the club" !

Yes, you understand why I wanted you to look at those.

Here's the thing, millions and millions of systems out there that are NOT pumping away, and they seem to work fine. But when it comes time to do some work on the system, you have a heckuva time getting all that air out.

By pumping away from the tank connection, the pump adds it's head pressure to the static pressure in the system, compresses those air bubbles and makes them more 'motivated' to move on out and into the air-catcher.

BUT, unless you can do the work yourself, it's gonna cost a bit to have a pipe man to come in and rearrange things for you, and winter is not the time for that kind of work! I just wanted to throw this out there as a possible "fix it once and for all" solution to consider.

Alternately, have someone in to fit bleeders to all the downstream ends of your baseboards/radiators and bleed the heck out of the system for a couple weeks.
 
  #12  
Old 12-19-12, 05:58 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
my expansion tank appears to be on the return, and from the looks of it, the circulator is at the beginning of the run, "pushing" water thru the system until it returns back and hits the expansion tank and finally on to the boiler.....or is it the other way around ?
I think it's the other way around.

Your pump is sucking on the return straw, and IN to the boiler. Expansion tank is on supply OUT of boiler. Pump is pumping toward the expansion tank with the boiler in between.
 
  #13  
Old 12-19-12, 06:13 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Yes, I just checked and realized the pump has an arrow, and that is the direction of the flow....so, when the water comes out of the boiler, the first thing it hits is the expansion tank.....which I assume is what you want.....right ?
 
  #14  
Old 12-19-12, 07:42 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
so, when the water comes out of the boiler, the first thing it hits is the expansion tank.....which I assume is what you want.....right ?
No... not necessarily...

The actual location of the tank in relation to the boiler is not what's MOST important here.

It's the PUMP in relation to the tank.

Where ever the tank is located, either on the supply or on the return, the pump must be pumping away from the tank.

There IS an added benefit to having the air scoop (and thus the tank) on the hot supply side though. When the water is HOTTEST is when the air comes out the easiest.

So, by having the tank on the supply side, as you do now, is the 'best' location for it. The PUMP would need to be moved to the supply side also... in this case.
 
  #15  
Old 12-19-12, 08:30 PM
Member
Join Date: Oct 2008
Location: USA
Posts: 2,922
Received 8 Votes on 8 Posts
No, that isn't the preferred arrangement.

A few decades ago, some sharp person explained why ideally the expansion tank should be on the circulator suction. The logic is irrefutable and widely accepted by most everyone.

Yet, there are many thousands, perhaps millions, of successful installations configured like that shown in fxcardin's photos, including mine. Since at least the 1930s, Bell & Gossett suggested that arrangement - and they still do, but I don't know exactly why, except maybe it goes along with their airtrol fittings and the conventional expansion tank: http://s3.pexsupply.com/product_file...06-Service.pdf
 
  #16  
Old 12-20-12, 09:27 AM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Yeah, so.....

Water comes out of boiler, goes thru pipes, hits expansion tank/air scoop, then continues on to zone manifold, etc.....eventually returning to the boiler at which point it hits the circulator.......so by definition, the circulator is "pulling" water away from the tank...........it's a good distance away when you consider the length of the zones, etc, but it is pulling.
 
  #17  
Old 12-20-12, 10:33 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Yes, if you look at it that way... but you are missing the point.

Whenever water flows in a pipe, there is pressure drop due to friction. You need to minimize the pressure drop between the pump and the POINT OF NO PRESSURE CHANGE, which is the point at which the tank is connected to the system.

The suction side of the pump need to be CLOSE TO the tank connection, not all the way around the entire system.
 
  #18  
Old 12-20-12, 12:15 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Gotcha.

Thanks for the help.
 
  #19  
Old 12-23-12, 03:30 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Update: looks like I fixed the noise problem.....I discovered the valve on top of the air scoop was stuck.....let a bunch of air out....no noise for 3 days.
 
  #20  
Old 12-23-12, 04:11 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Good deal! I like when it's a simple fix. to you to!
 
  #21  
Old 01-14-13, 07:36 PM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Hey I'm baaaaack !!!.

Just a follow up....the pipes have been quiet as far as the water rush, but I still get the expansion cracking noises. Is there any way to mitigate those ?. Also, I keep checking the air scoop, and every time I loosen the cap, air comes out. Being that I'm coming up on a month of doing this every 2-3 days, am I dealing with residual air, or do you think I have air leaking IN somehow.

Thanks.
 
  #22  
Old 01-14-13, 09:28 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
Being that I'm coming up on a month of doing this every 2-3 days, am I dealing with residual air, or do you think I have air leaking IN somehow.
I'm thinking it's still driving the air out. Has the boiler had to go to high limit yet? It's been warm here so I'm guessing not. You could try pushing the t'stat way up and letting the boiler get good and hot a couple times. That will drive the air out more quickly.

I did my new install at the beginning of this season and I'm still getting some air ... yes, very little at this point, but still some. It's been what, 3/4 months now? 300+ hours of operation.

It does take a while.

I still get the expansion cracking noises. Is there any way to mitigate those ?
It's often pretty difficult to locate exactly what the origin point of the noise is... but if you are able to pin it down, there may be some things you can do.

If the pipe is passing through a hole in a wooden framing component, and the pipe is resting on the wood, sometimes cutting plastic shims from a milk bottle and sliding them under the pipe will reduce the friction and eliminate the noise.

See if you can pin down a location and look for anywhere that the pipes are possibly rubbing wood.

By the way, when you remove the pics that you've previously linked to, all your links are now broken. See your previous picture post... all gone! I can't reference them anymore... oh well.
 
  #23  
Old 01-15-13, 09:56 AM
Member
Thread Starter
Join Date: Feb 2005
Location: Northern New Jersey
Posts: 446
Received 0 Votes on 0 Posts
Yeah my photobucket account went to hell.....thanks.....I'll keep bleeding air.
 
  #24  
Old 01-19-13, 04:42 PM
Member
Join Date: Jan 2013
Location: usa
Posts: 1
Received 0 Votes on 0 Posts
air in the hot water lines only

air in the hot water lines only
 
  #25  
Old 01-19-13, 09:20 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
OK... now there's a post that doesn't seem to be asking anything.

TWARD, what are you trying to say? Do you have a question?
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: