Leaking Presure release valve

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Devans175

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The pressure release valve on my boiler seems to be leaking. When the boiler fires up for a heat call and the pressure builds up, the pressure release valve starts to drip. As the pressure gets higher, the drip gets worse.

The boiler has a tag on it that says the "Maximum Working Pressure" is 30 PSI.

The guage on the boiler indicates that the pressure is topping out at 45 PSI.

I put my hand on the extrol tank and the top 25% (where the inlet is located) of the tank was hot. The rest of the tank seemed empty when I tapped on it.

The temperature on the guage is topping out at 200 degrees. I'm almost certain the high and low temps are set at 160/180. (I didn't have time to take the cover off to check the settings before I left for work this morning.)

My question is, is the leak a symptom of a bigger issue? I want to be sure that the service tech for the heating oil company looks at it properly. They hire alot of hacks this time of year. Also, the pressure valve is not cover in my service contract.
 

Krow

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My question is, is the leak a symptom of a bigger issue? I want to be sure that the service tech for the heating oil company looks at it properly. They hire alot of hacks this time of year. Also, the pressure valve is not cover in my service contract.
You have an expansion issue. I assume you have a a cushion tank in the ceiling of the basement near your boiler. Shut off the water inlets to that tank, shut down the boiler and drain the tank. (Hopefully you have a way to have air enter the tank so that it may drain quicker. Once you are satisfied that the tank is empty close any drainvalves and open your water inlets to the tank and leave them on. You want the tank about 50% full of water and 505 full of air. Make sure you boiler pressure is between 12-15 psi

That should stop your relief valve from leaking, if it does not and boiler pressure gets to 20 psi without the boiler calling for heat, then you have an issue with athe PRV.(pressure reducing valve)
 
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Devans175

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Is a cushoion tank the same as an extrol tank? The tank I have was installed last year when I had a Spirovent installed. It's grey, about 16 inches tall and it has an air valve on the bottom.
 

Krow

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Is a cushoion tank the same as an extrol tank? The tank I have was installed last year when I had a Spirovent installed. It's grey, about 16 inches tall and it has an air valve on the bottom.
Yes, if you don't have a large tank in the ceiling, that would be the one. Whats its diametre? On those tanks, there is no way to drain them and its unlikely that it failed.

Your next step is to diagnose/check your PRV is stopping the system pressure at 12- 15 PSI. Sometimes a little bit of sediment will clog up the diaphram and let more water into the system
 

Devans175

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Without being there, I'd guess the diameter is about 11 or 12 inches.

I think from how you've replied that assumption that the leak is a symptom of a larger problem. I do have a service contract and I'm going to give the tech a chance to diagnos it. The appointment is for tomorrow 2/13. I'll reply again with the diagnosis and go from there.

Thanks for your help and for any additional advice you or anyone else can provide.
 

Jadnashua

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The T&P valve is doing what it is designed for, assuming the gauges are right. Two things can cause excessive pressure - a defective expansion tank or a leak. the leak would have to be from a pressurized source - either from the autofill valve, the shutoff valve if you don't have an autofill valve, or maybe a cross-connection if you have an immersion heater for DHW or possibly from an indirect WH if you have one of those. Otherwise, the boiler can't just make excess water. With the pressure you have, it's not making steam, so it is just related to the volume of water.

The expansion tank is factory filled to around one atmosphere or 14-15 pounds. While the system is filled, the pressure would be the same as the system's gauge, so to check it, you'd need to turn the boiler off, depressurize the system, then check the air pressure. If you check it and any water comes out, the bladder is shot and it needs to be replaced. While they usually last longer, if the pressure got that high, the bladder may have ruptured. It certainly reduced its life since it isn't designed to stretch that far. Half full under normal circumstances would indicate a problem - too much pressure in the system, or not enough in the bladder.
 

Devans175

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So if I want to check to see if the boiler's guage is correct, can I put an air guage on the valve of the extrol tank while the boiler is at it's high temperature. If I understand what you wrote, the boiler's pressure guage should match the pressure in the extrol tank. I'd like to eliminate the faulty guage possibility.
 

Jadnashua

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Yes, in a closed system, the pressure is the same everywhere (well, for practical purposes anyways). If you get any water out of the schrader valve on the expansion tank, it is shot, replace it and that may solve your problem. But, to check its precharge, it must not have pressurized water on the inlet, as the water will come in, compress the air until the pressures on both sides of the bladder are identical.
 

helix3

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I had the same scenario on one the other day, it would drip when the boiler was running. I opened the release valve for a second using the lever, then rapped it a few times with a hammer. It's been 3 days with no drip. The temps around here have been in the teens so I know that the boiler is being used. I didn't check any system pressures but will do that to make sure there isn't another problem looming.
 

Jadnashua

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A properly working closed-loop boiler system should not change pressure much throughout a heating cycle, even if you shut the boiler off, it should remain fairly constant. This assumes that you install the tank and start it up with the boiler cold. Then, only the expansion volume is absorbed by the tank. If it is already hot and you install one, the pressure may drop since there may not be enough in the tank to replenish it. Then, if you have an autofill valve working properly, it will restore pressure and it should work fine from then on.
 

Devans175

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An update on the leaking T&P valve...

The service tech from the heating oil company came to check the leak. I discussed some of the comments you all made. I tried to do it diplomatically, since he's the pro and I try not to tell anyone how to do their job, unless I have good reason too. The tech felt strongly that the T&P valve needed to be replaced. I let him go ahead with it. My feeling was that, if he was wrong, the worst thing that would happen is I have a new T&P valve. If I didn't let him, I'd have no real way to argue that something else needed to be corrected. I had him replace the Temp/Pressure guage at the same time since it was giving different readings than the pressure I measured at the extrol tank.

The leak has stopped, but I'm going to monitor the temperature and pressure to be sure the problem is fixed. Once I monitor the situation for a few more days, I may ask for some more advice.

Thanks!
 

Jadnashua

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The spring on the T&P valve can wear out, so it could be bad. Also, once it is opened when it hasn't been for awhile, deposits will sometimes prevent it from sealing properly again. If the pressure truely does go up high enough to force it open, there is another problem in the system...and this is only the symptom.
 
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