Water dripping out of boiler valve

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GG_Mass

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Hi,
Water is dripping down the pipe shown in the picture. Only happens when the boiler is working, and a few minutes after it's done.

Is a replacement of the valve needed, or it is an internal problem in the boiler ?
Thank is advance for you advice.

Valve, joined with boiler

Pipe at the bottom, where water is dripping from.
 
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Reach4

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Do you have an expansion tank? It should normally be empty of water when not recently heating. It probably needs replacing.
 

GG_Mass

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Do you have an expansion tank? It should normally be empty of water when not recently heating. It probably needs replacing.

Yes, I do. And it seems like one of the newest parts of the system. I touched it, and it's not warm to the touch (if it should be). Can a valve leading to the tank be damaged ? (just shooting in the dark here..)
 
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Reach4

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You could check the air precharge, which is normally done when the system is not pressurized.

When the system is colder, you should be able to rap on the tank, and it should sound empty.

If water comes out when you check the precharge air pressure, the tank has failed. It is possible this tank is undersized for your system.
 

GG_Mass

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You could check the air precharge, which is normally done when the system is not pressurized.

When the system is colder, you should be able to rap on the tank, and it should sound empty.

If water comes out when you check the precharge air pressure, the tank has failed. It is possible this tank is undersized for your system.

If I understand correctly, I should:

Shut the system off for 4 hours

rap on the tank and it should sound empty

when rapping on the tank, if water drips from valve's end pipe (the same one that is leaking when the system's running), I may have a problem with a failed expansion tank.

Am I understanding you correctly ?

Thank you.
 

Reach4

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Shut the system off for 4 hours

rap on the tank and it should sound empty
The reason that the tank should be empty is that the air precharge should be as high or higher than the water pressure. The air pushes on the diaphragm in the tank, and the diaphragm squeezes out the water.

when rapping on the tank, if water drips from valve's end pipe (the same one that is leaking when the system's running), I may have a problem with a failed expansion tank.
Rapping on the tank is unlikely to trigger dripping. That was only to see if the tank sounds hollow or has water in it.

The valve I was referring to is the Schrader air valve at the bottom of the tank. You check the air pressure there, and fill with air initially. If water were to come out as you check the air pressure, that would mean that the rubber diaphragm that separates air and water leaks.

If the water pressure were higher than the air precharge, even on a good tank, the air pressure measured would be the same as the water pressure. That is because water pushes into the tank, and compresses the air. It is possible that air could slowly diffuse thru the diaphragm. So the pressure could be low, but the tank has not failed.

It is possible that the air pressure is just low in the pressure tank. Typically these come from the factory with 12 PSI of air. That would be good for a boiler with the refill set to maybe 10 PSI or less.
 

GG_Mass

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It is possible that the air pressure is just low in the pressure tank. Typically these come from the factory with 12 PSI of air. That would be good for a boiler with the refill set to maybe 10 PSI or less.

Understood.
I have a reliable automotive pressure gauge ( in my toolbox, at work), I'll bring it home tomorrow and check the state of the preCharge.

I'm assuming at complete rest (system not working, been off for 4 hours), the pressure should be ~12PSI ?

According to the warning label, if the pressure is lower than 12PSI, there's not much I can do -

"Do not adjust the pressure or re-pressurize this tank except for any adjustments at the time of the initial installation".

Do you agree ?
Thank you.
 
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Reach4

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According to the warning label, if the pressure is lower than 12PSI, there's not much I can do -

"Do not adjust the pressure or re-pressurize this tank except for any adjustments at the time of the initial installation".

Do you agree ?
No. I have no idea why that label says that. I don't know why the lawyer talked the marketer into that.:mad:

Do you have a pressure gauge for the boiler water? I would think that should be normal to have.
 

GG_Mass

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Yes, I hope this is the one you're looking for:
The system has been off for 2 hours.

The needle is between 20-25 PSI.
 
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Dana

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The pressure should be set to ~12-15psi when cold. It seems this system has been over-filled (by error, or by a seeping auto-fill valve, or possibly a leak in the isolating heat exchanger shown in in the picture in response #3.)

An idling pressure of 20-25 psi isn't usually necessary unless the building is 4+ stories tall, and it will require re-fitting the pressure relief valve on the boiler to something higher than 30 psi. Most boilers are rated for 50psi (max) operating pressure, but are normally shipped with 30psi pressure relief valves.

With the system down to a safe (<120F ) temperature you can bleed of system pressure from any operable purging port until the gauge reads 12 psi. There is usually a valve with a hose connection somewhere on the near-boiler plumbing. If there are no purging port valves, you can alternatively manually operate the pressure relief valve (with the flip lever on top ) to bleed system pressure. Try that first, then fire it up, and note where the pressure peaks at the end of a burn cycle. It may be just fine, staying below 25 psi, and WELL below the 30 psi of the pressure relief valve.

The air preset on the tank needs to be whatever you set the system pressure to. Setting the pre-charge on the tank can only be done when the system side of the tank is de-pressurized. If the tank can be isolated with valves, the pressure on the system side of the tank can be bled off by unscrewing it partially to letting a some water dribble. The amount of water that comes out could be considerable (on the order of a quart or more) if the system is at 20 psi and the tank was pre-charged to 12 psi. Check the air pressure only after that significant water has been bled, and adjust as-needed with an air pump.

The tank should only ring when tapping on the end with the air valve. The end plumbed to the system will be full of water, and will deliver more of a thud than a ring.
 
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Reach4

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The air preset on the tank needs to be whatever you set the system pressure to. Setting the pre-charge on the tank can only be done when the system side of the tank is de-pressurized. If the tank can be isolated with valves, the pressure on the system side of the tank can be bled off by unscrewing it partially to letting a some water dribble. The amount of water that comes out could be considerable (on the order of a quart or more) if the system is at 20 psi and the tank was pre-charged to 12 psi. Check the air pressure only after that significant water has been bled, and adjust as-needed with an air pump.

The tank should only ring when tapping on the end with the air valve. The end plumbed to the system will be full of water, and will deliver more of a thud than a ring.
I think that until the water pressure is above the air precharge pressure, the expansion tank should be empty.
 

GG_Mass

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Okay.
When I'll be back home today, the system will be resting for 16 hours already.

I'll make a note of the boiler pressure, and try to bring it down to 12-15 PSI, then check the tank's pressure.
Then fire up the system, and see how the pressure changes in the boiler and in the tank.

I'll post my reply with new information, hopefully it's helpful. I won't add pressure to expansion tank until I fully get what I'm doing.
Thank you.
 

Reach4

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I'll make a note of the boiler pressure, and try to bring it down to 12-15 PSI, then check the tank's pressure.
Then fire up the system, and see how the pressure changes in the boiler and in the tank.
I suggest you first monitor the pressure without firing up the boiler. It should not rise, but if it does, that will be telling.
 

Dana

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Okay.
When I'll be back home today, the system will be resting for 16 hours already.

I'll make a note of the boiler pressure, and try to bring it down to 12-15 PSI, then check the tank's pressure.
Then fire up the system, and see how the pressure changes in the boiler and in the tank.

I'll post my reply with new information, hopefully it's helpful. I won't add pressure to expansion tank until I fully get what I'm doing.
Thank you.

The tank pressure will read the same as the system pressure unless it's isolated from the system with the water pressure bled off, or unless the pre-charge air pressure it higher than the system pressure. Even if the tank has a pre-charge of 0 psi, the air pressure would measure close to the system pressure when the system side of the tank is pressurized.

So, if you reduce the system pressure to 12 psi and the air pressure matches, it doesn't tell you if it has been pre-charged correctly. But if the pressure rises rapidly to 25 psi or higher during a burn cycle, it probably isn't pre-charged correctly. But if it stays under 20 psi even when the boiler hit's it's high limit means you're going to be OK at whatever the precharge level it happens to be.

Heating systems with high-volume radiators will usually need a large-ish expansion tanks, and will see larger pressure swings from cold to fully-hot. Systems with fin-tube baseboard, not so much. Given the modestly sized near-boiler plumbing in the pictures I'd hazard that you don't have high-volume radiation on your system.

Do I assume correctly the heat exchanger is for heating potable hot water?
 

GG_Mass

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Do I assume correctly the heat exchanger is for heating potable hot water?

Yes, that's correct.

I came home now, the system has been off for more than 15 hours.

Pressure in boiler did not change, needle is at 25 PSI.

Pressure in expansion tank is 16.8 PSI.
I'm not sure what to make of this (good, bad, normal)...
 

Wrot

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25Psi is too high, unless the top of your highest radiator in your house is at 57.75 feet. What is the height of the highest radiator in the building? Also, you have to check the air precharge in the expansion tank with 0 pressure on the boiler. The precharge pressure should be the same psi as the boiler pressure.
 

GG_Mass

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25Psi is too high, unless the top of your highest radiator in your house is at 57.75 feet. What is the height of the highest radiator in the building?

It's a single story home, with a basement, the boiler is in the basement. I'm not sure how height is calculated for this application, but not - I don't see how it's 57.75 feet high.

I must say - the system has been like this since we moved in, 5 years ago, the pressure has been around 25PSi in the boiler , since I can remember.. Feels weird how this happened "all of the sudden".
Also, you have to check the air precharge in the expansion tank with 0 pressure on the boiler. The precharge pressure should be the same psi as the boiler pressure

How do I bring down the pressure in the boiler to 0 ?
 

Wrot

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1 psi will raise a column of water 2.31 feet.
25 psi x 2.31 feet = 57.75 feet
Usually a bungalow is set at the exp. tank precharge of 12 psi.
Turn off the feed valve to the boiler, if there is an automatic air vent on the boiler , screw the cap closed. Open a boiler drain and drop the boiler pressure to 0 psi then close the drain valve. then check the precharge in the exp. tank.
If the tank is precharged at 12 psi, the back off the feed valve to 12 psi.
 

GG_Mass

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1 psi will raise a column of water 2.31 feet.
25 psi x 2.31 feet = 57.75 feet
Usually a bungalow is set at the exp. tank precharge of 12 psi.
Turn off the feed valve to the boiler, if there is an automatic air vent on the boiler , screw the cap closed. Open a boiler drain and drop the boiler pressure to 0 psi then close the drain valve. then check the precharge in the exp. tank.
If the tank is precharged at 12 psi, the back off the feed valve to 12 psi.

Everything you said is pretty clear, besides - "back off the valve to 12 PSI" - Once I open what I consider the feed valve - a quarter turn ball valve , the water would just flow in, and create the same pressure as I currently have. (no?)

I must be missing on the actual valve that you mean, I'll look for it.
 

Wrot

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The pressure reducing valve is just behind the heat exchanger next to the drain valve (I can only see part of it in the picture). It has a blue or grey top. Unscrew the bolt on the top of the PRV almost all the way out. Then open the ball valve to start filling the system, after 15 min check the pressure gauge, if it's not at same pressure as the exp. tank (12 psi). Turn the bolt in a bit and wait a few minutes. repeat this until the pressure is where you want it.
 
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