Expansion Tank Lost its Precharge - Radiant Heating System - Is My Tank Failing?

Reply

  #1  
Old 02-07-17, 02:58 PM
C
Member
Thread Starter
Join Date: Aug 2009
Location: NJ
Posts: 36
Received 0 Votes on 0 Posts
Question Expansion Tank Lost its Precharge - Radiant Heating System - Is My Tank Failing?

Hi all,

I have a radiant heating system. I use a Vertex to provide domestic water for my system as well as hot water for the radiant heating system. I am doing my yearly checks on the system. I noticed recently when my Taco pumps shut off because heat requested ended, I was getting a stuttering sound in my pex tubing. I figured it was something to do with the expansion tank. I thought it might be full of water as I had one fail a year ago.

The expansion tank is located right before my hot water heater. My city water pressure fluctuates between 55psi and 65psi. I took my expansion tank off because I have read that is the only way to get the correct reading. My expansion tank was filled to 60 PSI but now when I checked it, it was down to 5 PSI. So this is likely the cause of the stutter.

My question is, is my expansion tank failing or was it that I didn't tighten the cap at the bottom with a tool? I tightened it by hand as hard I could so I wouldn't break the plastic.
 
Sponsored Links
  #2  
Old 02-07-17, 03:28 PM
C
Member
Join Date: May 2015
Location: USA
Posts: 3,138
Received 2 Votes on 2 Posts
I assume this tank has a bladder. The ones without bladders will absorb the air over time.

If it's leaking out the Schrader valve, it's not because the cap isn't tight, it's because the valve stem is leaking, or may just be loose. I suggest you get a valve stem tool and replacement stem and swap it out. Then after you refill it, squirt some soapy water into the valve area and see if you see any leak (you will get bubbling in the area). A really slow leak won't necessarily show, but many will.
 

Last edited by CarbideTipped; 02-07-17 at 03:50 PM.
  #3  
Old 02-07-17, 03:45 PM
C
Member
Thread Starter
Join Date: Aug 2009
Location: NJ
Posts: 36
Received 0 Votes on 0 Posts
Hey Carbide yes its a THERM-X-TROL ST-5.

Good idea I have the valve stem tool. I'll give it a try. After filling it now I put the old saliva on it and didn't see any bubbles. Might have to wait a bit longer.

Just left wondering if maybe there is a pin hole leak in the diaphram thinking more about it. Big drop is PSI
 
  #4  
Old 02-07-17, 03:49 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,998
Received 50 Votes on 47 Posts
C,
There should never be any water in the bottom of the tank. The bladder is in the bottom and water in the top. If you have a water leak at the valve replace the tank.

I believe those tanks come factory precharged at 40psi. When your read 60 that was your system pressure. Removed it should have been at least 40, more if an additional charge was added to match your system pressure.

You can try to recharge to 55 if that's what your system is running. That blue plastic is only a protective cap and finger tight is fine. Has nothing to with the air charge.

Hope this helps a little.
 

Last edited by spott; 02-07-17 at 04:08 PM.
  #5  
Old 02-07-17, 05:19 PM
C
Member
Thread Starter
Join Date: Aug 2009
Location: NJ
Posts: 36
Received 0 Votes on 0 Posts
Question Copper to Steal Do I need a Brass Fitting

Thanks Spot, yes the tank was suppose to come factory at 40 PSI. If I recall it was 30 something instead. I charged the tank to 60 PSI to match city pressure.

I just took my schrader valve tool and tightened the valve. I know they shouldn't be overly tightened because they have a seal that should take up the slack. But after checking now I felt the slack was excessive. I saw not bubbles coming out after tightening it.

QUESTION: Just looked at the connection between my copper fitting and the steel tank and noticed some rust. This caused me to read my heating system instructions. I just noticed that there is a line in there that says:

"The expansion tank is made out of steel and should not be screwed into a copper fitting, if you must install it on cop-per put a brass coupling between them."

Anyone chime in on this? What the heck would this fitting look like?
 
  #6  
Old 02-07-17, 05:53 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 2,998
Received 50 Votes on 47 Posts
C,
They must be worried about steel directly into potable water. Use a brass nipple then the brass coupling and then the tank. A coupling is just a fitting with threads on both ends to join 2 threaded connections together. Very common fitting.

Google brass coupling and you will see what they are.
 
  #7  
Old 02-08-17, 05:30 PM
G
Member
Join Date: Oct 2008
Location: USA
Posts: 2,981
Received 11 Votes on 11 Posts
I assume this tank has a bladder. The ones without bladders will absorb the air over time.
That's opposite of the real truth. Bladder-type tanks will continuously lose air as it diffuses through the membrane, and is lost to the atmosphere. They always go flat in a few years.

Conventional steel tanks have air dissolved into the water, but, properly piped, the air is continuously removed from the circulating water and returned to the tank. A conventional steel tank goes for decades without becoming waterlogged.
 
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: