The hot water heating system's water pressure should be 0?

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Old 11-29-20, 08:53 PM
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The hot water heating system's water pressure should be 0?

My house is a one-floor ranch house in the Boston area. I have a gas hot water heating system. I can hear loud air exploding sound from the basement pipe sometimes. So I am always trying to get all the air out of the system. I have a panel baseboard on the first floor which is the highest point in the system. I can bleed trapped air there. It works very well when the heating is called. Because the system is connected with the house water system directly, I thought there should have water coming out if I open the bleeder long enough when the heating is NOT called. But there is NO water! Is there anything wrong with the system? Does this mean there is no water pressure in the system? The system is about 11 years old. Any component should be replaced?




 

Last edited by PJmax; 11-29-20 at 09:41 PM. Reason: resized pics/added circle
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Old 11-29-20, 09:45 PM
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The loud exploding sound is your boiler probably boiling. If the pressure gauge is accurate..... you have almost no pressure in your system. You put an arrow pointing to the cold water line. I added a circle to the fill valve.

There is a handle on the fill valve. You should be able to pull it up and hear water enter the boiler. Make sure the boiler is cool before adding water. Try that and see if the boiler starts to fill. Keep an eye on the pressure gauge. The gauge is marked around 16psi.
 
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Old 11-29-20, 10:05 PM
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I will try that tomorrow. The mark on the pressure meter was marked by me then the system is on. When the system is off (no heat is needed), the water pressure is 0 as shown in the pressure meter. I thought the system should have some water pressure even when the heat is not called.
 
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Old 11-29-20, 10:16 PM
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Are you saying when cold the system is 0 psi and 16 psi when hot ?

That would indicate the fill valve is not replacing the water. You should have a standing pressure of at least 14 psi with some increase with heat. Too much rise with heat.....over 22 psi or so.... indicates a pressure tank issue.
 
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Old 11-29-20, 10:23 PM
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yes. when cool the pressure is 0, when hot it is about 16 psi.

then I need to find how the fill valve works.
 
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Old 11-29-20, 11:31 PM
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That's a combo fill valve and backflow preventer. Should be similar to the link below.
There is a short video and spec sheet at the bottom.

Watts fill valve info


Make sure that blue PEX water line to the boiler is turned on at the manifold if you have one.
 
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Old 11-30-20, 08:36 AM
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Thank you, PJmax.

I left the fill valve lever a little this morning. I heard the water flowing noise and then released it. The water flowing noise stopped. Nothing changed. 1 minute later I left it a little again then released it again. This time the water flowing noise stays for a while until the pressure reached about 15 psi. It is normal now! I think the fill valve was blocked somehow. It is working now, I think. Thank you,
PJmax. You are the hero!
 
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Old 11-30-20, 08:38 AM
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Boiler water pressure gauges are often way off and should be verifiied. Here are old DIY links on subject

https://www.doityourself.com/forum/b...ure-gauge.html

https://www.doityourself.com/forum/b...d-buy-one.html

Along with gauge on boiler, I have second 4" one near regulator that is more accurate and easy to read when checking or adjusting.
 
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