leaking pressure relief valve


  #1  
Old 03-29-10, 11:57 AM
D
Member
Thread Starter
Join Date: Sep 2003
Location: usa
Posts: 99
Likes: 0
Received 0 Likes on 0 Posts
leaking pressure relief valve

i have small american standard nat gas boiler, model gpr80 1bj1.

i went on vacation for 3 months, draining the water pipes before leaving. since coming back my pressure relief valve drips water constantly. water pressure is @26 psi. expansion tank pressure is 15psi measured at the shrader valve.

any ideas on what the problem might be? the boiler seems to be running fine otherwise.
 

Last edited by driger; 03-29-10 at 12:58 PM.
  #2  
Old 03-29-10, 12:36 PM
E
Member
Join Date: Jan 2010
Location: PA
Posts: 33
Likes: 0
Received 0 Likes on 0 Posts
water pressure is @26 psi.
What's the tempertaure at when the pressure is @26 psi
 
  #3  
Old 03-29-10, 01:45 PM
D
Member
Thread Starter
Join Date: Sep 2003
Location: usa
Posts: 99
Likes: 0
Received 0 Likes on 0 Posts
water temp is 170f at 26psi.
 
  #4  
Old 03-29-10, 03:34 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Likes: 0
Received 8 Likes on 6 Posts
First, everybody knows how I distrust gauges. If your gauge is accurate, then the relief valve should not be leaking, being that it's set at 30 PSI. Before you go too much further, perhaps the best thing to do is verify that the gauge is good. You can do this by picking up adapters at HD or Lowes or plumbing supply that will allow you to adapt a 0-30 or 0-50 pressure gauge to one of the boiler drains. If you go to the section where lawn sprinkler stuff is, you can pick up a gauge for this purpose for about $10... problem is that it will be a 0-200 or 0-300 PSI gauge and that's useless for reading low pressures. But if you pick up one of those, you can remove that gauge and install another one in it's place... I don't think you can get the fittings for $10 separately.

What is the pressure when the system is cool? It's possible that the pressure reducing valve is leaking through and over pressuring the boiler. When you refilled the boiler, you may have picked up 'crud' from the water line and it got stuck in the reducing valve causing it to leak. If, when the boiler cools, the pressure does not RETURN to 12-15 PSI, this may be the culprit.

The relief valve MAY be NFG... and if it's more than 5 years old, I would say to go ahead and replace it anyway.

Next, how did you check the charge in the expansion tank? Reason I ask is that if there was any pressure in the boiler, you did not get an accurate reading. You need to drop the boiler pressure to zero before you can get a good reading from the schrader. If you were reading 15 PSI on the tank when there was 26 in the boiler, then for certain either your tire gauge, or your boiler gauge is in error...

Did any water come out when you press the pin on the schrader? If so, the bladder inside is shot and the tank needs replaced.

Here's a write-up on how you can check the tank pressure and recharge properly:

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

1. Shut off boiler and allow to cool to under 100F.

2. Shut off water supply line to boiler.

3. Drain only enough water from the boiler drain to drop the system pressure to ZERO. You do NOT need to completely drain the system. Only drop the pressure!

4. With an ACCURATE tire pressure gauge, check the air charge in the tank on the air valve opposite the end of the tank that's connected to the system. If ANY water comes out of the air valve, the bladder inside the tank is shot and the tank needs replaced. If no water comes out the air valve, and the pressure is less than 12-15 PSI, continue to step 5. If the pressure is OK, turn the water supply to the boiler back on and repressurize the system, turn the power back on to the boiler, no service is necessary.

5. Using a bicycle pump, or a small air compressor, add air to the tank until you have 15 PSI air charge.

6. Check the boiler pressure gauge again, and if it has risen off ZERO, drain some more water from the boiler drain until it is again at ZERO.

7. Check the air charge on the tank again. If it is below 15 PSI, add air to the tank until it is at 15 PSI.

8. Repeat steps 6 and 7 until the boiler stays at ZERO and the tank stays at 15 PSI. At this point, the tank is properly recharged and the water supply can be turned on to re-pressurize the system, turn the power on to boiler and return to service.
 
  #5  
Old 03-29-10, 05:02 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by NJ Trooper View Post
First, everybody knows how I distrust gauges.
For a bladder-type expansion tank, wouldn't a gauge-glass be helpful for the water side? Yeah, I know, they don't make tanks like that. But maybe gauge-glass fittings could be added?
 
  #6  
Old 03-29-10, 05:40 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Likes: 0
Received 8 Likes on 6 Posts
Bladder type? I don't know how you could possibly add a glass to one... when the boiler is cold, there should be NO water in the tank, because the air pressure matches the boiler pressure. I don't even think a permanently attached gauge on the air side would do any good, because in general, it would read the higher of the two pressures, air or boiler...

But, we digress...
 
  #7  
Old 03-29-10, 05:42 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Location: United States
Posts: 2,644
Likes: 0
Received 42 Likes on 35 Posts
The gauge glass idea will not work as the air is on the bottom and the water is on top. Air would enter the glass and go into the system.
 
  #8  
Old 03-29-10, 08:20 PM
D
Member
Thread Starter
Join Date: Sep 2003
Location: usa
Posts: 99
Likes: 0
Received 0 Likes on 0 Posts
thanks for the discussion.

however, i opened the relief valve up for about 5 seconds and let the water flow, then let it snap shut.

thats seems to have solved my problem.
 

Last edited by driger; 03-29-10 at 08:37 PM.
  #9  
Old 03-29-10, 08:46 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Likes: 0
Received 8 Likes on 6 Posts
For now... you'll be back!
 
 

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