Boiler Overpressurizing & Relief Valve Weeping


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Old 01-12-07, 10:00 AM
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Boiler Overpressurizing & Relief Valve Weeping

I've continued to have the same problem with my heating system weeping a few ounces of water out of the pressure relief valve everyday. The system pressure falls to 10psi when the system is cool (<90 degrees), however, when the boiler heats to a steady 175 degrees the system pressure goes to 27psi and approaches 30 at which time the weeping occurs. The pressure reducer valve is functioning properly. My only other clue is that the expansion tank doesn't appear waterlogged as the tank pressue is 6 psi when cool and rises to 22 psi when the system is fully heated at 175 degrees and 27 psi.

Could the problem be that the Watts ET-30 expansion tank does not have enough starting pressure? Or that there's a pinhole leak in the bladder? Or could it be another problem? There's no shut off valve to the expansion tank for me to measure the expansion tank pressue off the system. Is there any way to adjust (increase) the pressure in the tank to a target via the Schrader value while the system is full of water? It seems to me that the Slant/Fin boiler and system should have a normal operating pressure of much less than 27-30 psi?

Any thoughts?
 
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Old 01-12-07, 11:23 AM
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Yes...

Pick a solution.

With the boiler shut off and any autofeeds as well...

A. If the tank has an isolation valve, close it, remove the tank and fill it to 12 to 15psi. Then replace it. Accurate and minimal water loss.

or

B. Drop the system pressure down to 0psi by letting some water out, pump it up to 12 to 15psi. Bring the system pressure back up to normal with the water feed.

Eiether way, you have to have more air cushion in there and you can't pump it up accurately without getting the water pressure neutralized.
 
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Old 01-12-07, 03:18 PM
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If that tank is more than 10 years old, I would just go ahead and replace the tank...

"Classic Symptoms".

The tank pressure needs to be checked either disconnected from the system, or the water side connection needs to be de-pressurized. Set the pressure in the tank just a pound or less BELOW the pressure that you set the system to cold (should be 12-15 PSI normally) so the tank will be 11-14 ...

Do you get any water out the Schrader valve ?

If you remove that tank, BE CAREFUL! I COULD BE FULL OF WATER! even though it may not sound like it. It will be HEAVY! PLAN FOR THE WORST CASE! HAVE A HELPER AT THE READY!

By the way, check out the search feature on the forum, you will find bazillions of posts about pressure tanks.

Good luck!
 
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Old 01-13-07, 06:55 AM
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How Do you Change an Expansion Tank?

The expansion tank is at least 8 years old. I suspect the expansion tank is bad as noted in other posts.
How do you change the tank? I see the steps involve at least: 1) shutting off the water supply; 2) draining the system. 3) Being very careful with the potential weight of the tank.

My set up appears pretty standard with the expansion tank threaded into the air separator unit. Is it as simple as unscrewing the fitting and tank? Does the new tank just thread on? Do you use Teflon tape or anything when installing the new tank?

Thanks much.

Shoe
 
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Old 01-13-07, 07:16 AM
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Yes, it basically just unscrews from the bottom of the air scoop.

You may not need to drain the system completely. You do however want to get the pressure to zero. You may get lucky and only have to drain a few gallons, depending on the location in the system of the tank, and whether or not there are valves you can close in order to isolate that section of the piping from the rest of the system.

Look for valves that can be closed in order to isolate.
Some pics would be helpful so we can see what yer working with.

When you re-install, add a ball valve between the tank and the air scoop!
This will make it SO much easier if it has to be done again! You can do this with two short nipples, the valve and perhaps a coupler. It's probably 1/2" threads. Use black pipe and fittings, the valve can be brass/bronze.

Big Box stores should have everything you need.

CHECK THE PRE_CHARGE in the tank before you install it, use a tire pressure gauge. Set for 12 PSI.

I like to use tape AND pipe dope on the threaded fittings. Rectorseal #5 is a pretty good dope. Use the pink teflon tape. Wrap a few turns of the tape clockwise on the male threads and the dope on top.
 
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Old 01-13-07, 07:45 AM
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Exclamation tank

Remember what Grady said. Eight gallons of water in a saturated tank will weigh over 40 pounds! It will be heavy!!! More than expected after hefting the new one.

Pete
 
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Old 01-13-07, 08:54 AM
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Don't twist the tank!!!

I don't know if it's been mentioned but don't twist the tank itself. Use a wrench on the attachment fitting when you loosen it off or put one one.
 
 

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