Pressure valve leaking even after replacement

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Old 10-18-18, 04:23 PM
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Pressure valve leaking even after replacement

I have a gas furnace that powers my hot water storage tank and baseboard heat. The pressure valve started to leak when furnace is heating up the water. I thought the valve is old and leaking so I have replaced it with a new one. Unfortunately, the new one leaks as well when water is being heated up. Any ideas what the cause may be? I have attached few photos of the system and my readings from meters.
 
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  #2  
Old 10-18-18, 05:16 PM
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D,
Check your expansion tank(extrol tank) you may have a defective bladder or low air charge.

The simplest test is to tap the tank, top and bottom with a screwdriver or something metal. The top should sound solid due to the water inside and the bottom should should hollow as that is where your bladder is.

If the whole tank is solid it is water logged so there is no place for the heated expanded water to go so your boiler builds pressure when heated and opens the relief valve which is set at 30 PSI,

If this is your problem you can either recharge the bladder if it just lost it's charge or the tank must be replaced.

You can check the charge with a tire pressure gauge by removing the red cap on the bottom of the tank exposing a Schrader valve.

In order to check the charge or to recharge the tank it must be isolated from the system with no pressure on it or it must be removed completely.

You are looking for 12-15 PSI air pressure in the tank.

Hope this helps a little.
 
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Old 10-18-18, 06:37 PM
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spott, I think you have found the issue. The simple knock test on the expansion tank sounds like it is full of water. Considering its age, the bladder most likely is gone so I will replace the whole tank. Will post back once I get the part and do the swap.
 
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Old 10-18-18, 09:53 PM
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Thread moved to the boiler forum. A furnace uses hot air
 
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Old 10-19-18, 04:20 AM
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That pressure gauge is reading about 25 psi which is a little high and that type gauge may not be reading correctly. What is the pressure rating of the boiler and of the replacement relief valve. The tag on the boiler will list the boilers safe pressure rating
 
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Old 10-19-18, 11:59 AM
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According to the label, my boiler's limits are:

Steam 15 PSI
Water 50 PSI
Minimum relief valve capacity: 125 MBH or LBS/HR
Maximum operating temperature 250F

Here is the label and today's readings from the gauges.
 
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Old 10-19-18, 12:02 PM
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What was the pressure relief rating or setting of the new relief valve you just installed? If the pressure gauge is correct and the pressure in the system is less than 20 psi when the new valve leaks then the new valve is bad and should be replaced under warranty.
 
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Old 10-19-18, 12:03 PM
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30 PSI (same as the old one)
 
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Old 10-19-18, 12:09 PM
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Yes, those are your limits which you are well within with the 30 PSI relief valve. You could increase up to 50 if needed which you don't if that's what you were asking.

It's just a typical residential boiler. That relief valve capacity is what it must be able to handle if it goes off which your does. That is why you cannot decrease the size of the pipe coming off the relief valve. It must be able to drain fast enough so it can relieve pressure fast than the boiler can build it to keep the boiler from exploding.

I hope that's what you were asking.
 
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Old 10-22-18, 05:09 AM
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This weekend, I have replaced the expansion tank with a brand new 4.5 gallon one. Air pressure of the tank was set to 25PSI. Unfortunately, that did not fix the problem. I did more checking and it looks like the pressure stays at around 10PSI when the boiler is not working but when it heats up, the pressure goes to 30-32PSI (based on the gauge). I guess at this time, the pressure relief valve is opening up releasing water.

Any other ideas what could be causing the pressure to rise above 30PSI when boiler heats the water up? Could there be an air in the system causing it or should I seek help of a plumber to get it fixed?
 
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Old 10-22-18, 05:36 AM
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Re-pressurise the expansion tank to 12-15 psi, that 25psi is too high for a starting point.
 
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Old 10-22-18, 06:53 AM
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Yep, with 25 psi in the tank, the bladder won't allow any expansion water until the system gets up to 25 psi. Depressurize the system before adjusting the tank pressure.
 
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Old 10-22-18, 06:59 AM
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Thanks. Will do that today when I get back home.
 
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Old 10-22-18, 11:21 AM
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d,
What is the size of your boiler? How many BTU's and what type of radiation is it heating. Is it standard aluminum finned baseboard, cast iron rads or a combination of both.

Your problem seems to point to an undersized extrol tank. You may need a #60.
 
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Old 10-23-18, 06:30 AM
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An update: I have relieved all pressure from the system, lowered the expansion tank's PSI to about 12-15 PSI (that's as accurate as my bike pump will go) and also lowered the temperature on the hot water storage tank by about 5 degrees F (my wife complained that the water is too hot). So far since yesterday evening, there is not a single drop of the water coming out of the pressure relief valve.

I will keep an eye on this for a few days but I thank all of you for a great support and providing input that helped me fix the problem.
 
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Old 10-23-18, 07:58 AM
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Careful there . . . . successfully fixing things yourself can be a confidence builder; and very addictive !
 
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