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Discussion Starter · #1 ·
hello.

i have a standard hot boiler water heater, and recently, i noticed that the relief valve will spill out some water (not excessive, may be half a pint of water) each time when the thermostat finished calling for heat. The water that comes out are very hot as i can see the steam from the water while its spilling onto the floor.

in other words, when the fire of the boiler seems to be stopping, then the water will come out from the relief valve.

I have googled a bit, and found usually leaks from relief valve is constant, and not after thermostat finished calling for heat. The expansion tank was replaced about 3 years ago. I am guessing its either the relief valve or the expansion tank itself.

however, would like to seek some opinion before replacing these parts.

Thanks
 

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Check your expansion tank pressure. That big gray tank over the boiler. You can check with tire gauge. If under 12 PSI replace, as well as replace the valve.
 

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Out of curiosity.....how old is that boiler? I am aware that they last a long, long time.
But it looks like it has seen better days.
 

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Ayuh,..... I kept clickin' on the picture, til it got big,.....

It's at 50 psi,..... pegged the gauge,......

Could be the tank, but I'd sooner think the auto-fill valve is stuck open,.....

Might need a new tank, 'n relief valve 'cause of it,.....

Ya might wanta just call a service tech,.....
 

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Ayuh,..... I kept clickin' on the picture, til it got big,.....

It's at 50 psi,..... pegged the gauge,......

Could be the tank, but I'd sooner think the auto-fill valve is stuck open,.....

Might need a new tank, 'n relief valve 'cause of it,.....

Ya might wanta just call a service tech,.....
I see what your saying, I didn’t enlarge the photo at first.
Boilers definitely over pressurized. OP is lucky the relief isn’t blowing off like crazy. It actually should be......
OP, you have several issues that need to be addressed.
 

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Discussion Starter · #7 ·
Hi

The boiler itself is only 10 years old. It’s a bit dirty, yes. :)

The valve isn’t stuck open. I tried lifting it up and it would spill out water. And stop when I let it go.

On the gauge, I found that there is a silver pin at 30 psi and there is another pin at 50 psi, which one is which? And why is there 2 pins?

I think to start with, I should replace the tank, and then replace the valve if it still happens.

Any chance the gauge is broken also? How can you tell?

Thanks
 

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Absolutely not, don’t start randomly replacing parts hoping to solve a problem.
Is the expansion tank full? Is the air charge right?
Is the auto fill leaking by?
Is there a domestic coil in the boiler that’s leaking into the boiler water?
Check boiler pressure with another gauge in a separate spot.
 

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Discussion Starter · #9 ·
Absolutely not, don’t start randomly replacing parts hoping to solve a problem.
Is the expansion tank full? Is the air charge right?
Is the auto fill leaking by?
Is there a domestic coil in the boiler that’s leaking into the boiler water?
Check boiler pressure with another gauge in a separate spot.
Will you be able to give me more info / details on checking these?

1) Is the expansion tank full? its feels hollow when i knock on it. How do you check the air charge?
2) What do you mean by , "Is the auto fill leaking by"? Leaking by what please?

Are you suggesting to check the pressure on the expansion tank itself? i will do that measurement tomorrow.

There isnt another pressure gauge along the pipes for me to see how much PSI there is in the water flow.

Thanks
 

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Absolutely not, don’t start randomly replacing parts hoping to solve a problem.
Is the expansion tank full? Is the air charge right?
Is the auto fill leaking by?
Is there a domestic coil in the boiler that’s leaking into the boiler water?
Check boiler pressure with another gauge in a separate spot.
Will you be able to give me more info / details on checking these?

1) Is the expansion tank full? its feels hollow when i knock on it. How do you check the air charge?
2) What do you mean by , "Is the auto fill leaking by"? Leaking by what please?

Are you suggesting to check the pressure on the expansion tank itself? i will do that measurement tomorrow.

There isnt another pressure gauge along the pipes for me to see how much PSI there is in the water flow.

Thanks
Ayuh,..... The expansion tank is checked at it's shrader valve,....
Should be 'bout 12 psi of air, no water,.....

The auto-fill valve is where the boiler system is fed water by the domestic water system,......
The domestic system is at a much higher pressure, the auto-fill only allows 'bout 12 psi into the boiler's side,....
If it's leakin', the boiler pressure goes to high,....

I believe the needle at 30 psi is the redline indicator, 'n the needle at 50 psi is the actual pressure,.....

The gauge is called a tridicator, 'n is replaceable, or they can be added into the system, anywhere there's a threaded port,.....
 

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Discussion Starter · #11 ·
thanks for the responses.

1) the expansion tank - no water inside, i will take pressure measurement
2) auto fill valve - no leaking
3) The relief valve seems to be functioning, as it let water go when its needed. and normally it doesnt leak water.

Question on the pressure measurement of expansion tank - at what pressure , means that you have to replace it? And is there any "standard sizes" to replace the expansion tank? I have googled and it seems pretty staright forward on replacing it.


thanks
 

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How do you know the auto fill isn’t leaking. We mean into the boiler, not leaking externally.
It may seem tempting to replace the tank but do not replace any parts until your issue is fully diagnosed.
 

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Discussion Starter · #13 ·
How do you know the auto fill isn’t leaking. We mean into the boiler, not leaking externally.
It may seem tempting to replace the tank but do not replace any parts until your issue is fully diagnosed.
okay, can you give me some pointers on how to diagnose it? the questions asked, is something that i do not know the answers to.

any help is appreciated.

thanks
 

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Just fix this exact problem on my boiler. The air tank was completely full of water. My tank is not a bladder so over time the air went away. My tank has a valve to isolate it from the boiler system. I turned it off and drained the tank dry and everything was good after turning the valve back on.
 

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okay, can you give me some pointers on how to diagnose it? the questions asked, is something that i do not know the answers to.

any help is appreciated.

thanks
You’ll need to determine if the auto fill is stuck open. Turn it off and drain down system pressure to a normal level.
 

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Another thing to consider is the size of the expansion tank. The bigger your heating system loop (s) the larger the expansion tank you need to accommodate the expansion. The manufacturers publish data on sizing, the ones I've seen are by square ft of heated living space. If you wind up replacing your expansion tank, I'd recommend getting one at least one size larger than the minimum size for your heating system. The expansion tank on my system is within manufacturer's spec for my size system, but right at the limit, I still get occasional discharge from my relief valve. I wish that I'd replaced it with the next size up when I replaced it.
 

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It sounds like your autofill valve is causing too much water into your system.

Most residential boiler systems should run at 15psi or less.

Shut off your fll valve, drain some water out of your boiler until the pressure is 14psi, and then start the boiler up and let it run for a few days. If the pressure stays in range and the relief valve stops blowing, then there you go.

As long as your boiler system is tight and not leaking you don't need an autofill valve. You can keep the main fill valve closed and leave it this way forever if you want to. You just need to check your pressure every once in a while and manually bump up the pressure from time to time if it needs it.

Where I live, autofill valves are actually not even allowed. Most systems seem to work fine like this without needing much attention.
 

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Discussion Starter · #18 ·
It sounds like your autofill valve is causing too much water into your system.

Most residential boiler systems should run at 15psi or less.

Shut off your fll valve, drain some water out of your boiler until the pressure is 14psi, and then start the boiler up and let it run for a few days. If the pressure stays in range and the relief valve stops blowing, then there you go.

As long as your boiler system is tight and not leaking you don't need an autofill valve. You can keep the main fill valve closed and leave it this way forever if you want to. You just need to check your pressure every once in a while and manually bump up the pressure from time to time if it needs it.

Where I live, autofill valves are actually not even allowed. Most systems seem to work fine like this without needing much attention.
Thanks for this comment. This is very instructive with explaination.

i will attempt this coming weekend.
 

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Discussion Starter · #19 ·
It sounds like your autofill valve is causing too much water into your system.

Most residential boiler systems should run at 15psi or less.

Shut off your fll valve, drain some water out of your boiler until the pressure is 14psi, and then start the boiler up and let it run for a few days. If the pressure stays in range and the relief valve stops blowing, then there you go.

As long as your boiler system is tight and not leaking you don't need an autofill valve. You can keep the main fill valve closed and leave it this way forever if you want to. You just need to check your pressure every once in a while and manually bump up the pressure from time to time if it needs it.

Where I live, autofill valves are actually not even allowed. Most systems seem to work fine like this without needing much attention.
Are all expansion tank all standard, with the difference on the size itself? Meaning, does certain brand of boiler must use certain brand of expansion tank? Or its just simply sizes, and the thread is standard?

thanks!
 

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Are all expansion tank all standard, with the difference on the size itself? Meaning, does certain brand of boiler must use certain brand of expansion tank? Or its just simply sizes, and the thread is standard?

thanks!
Xpansion tanks with bladder and schader valve all work the same way. As mentioned, get the correct size for your boiler.

you can google the chart showing what size xpansion your boiler needs. They are available at any big box store.

Good advice in post 17, to determine if your autofill valve is the issue. A new xpansion tank won't help if the autofill valve is stuck opened as pressure will still continue to build and eventually trip the relief valve once it gets up to 30 psi or so.

Hope you get it figured out and fixed soon takkie.
 
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