No water comes out when bleeding radiator

Old 12-08-20, 03:23 PM
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Unhappy No water comes out when bleeding radiator

Hello DIY's,
I have a hot water boiler for my Cape. With one radiator, I think last one on the line upstairs, no water comes out when I bleed air out. All the other radiators bleed fine The pressure on the old boiler is 15. How can I fix the problem? Would putting in a Durst auto bleeder valve fix it? Thanx for any help. JBCT
Old 12-08-20, 09:18 PM
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Install $8.29 Watts auto vent on radiators. Are very reliable and can be opened and serviced.
Make sure water feed valve to system is open and pressure gauge reads 12 psi.
Old 12-09-20, 03:40 AM
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I have to assume that the heating system does not have enough pressure in it , and that the pressure gauge on the boiler is not accurate. A column of water will rise 2.31 feet for every pound of water pressure or figuring another way you need .432 psi for each foot of height. If you measure from an accurate pressure gauge to the top of the highest radiator in your home and that figure is say 20 feet then you will need to have a pressure reading of 8.64lbs. (20 feet X .432 = 8.64#) and if the measurement is 30 feet then pressure will be 12.96#. Most new PRV's rated for boiler service come preset at 12 psi which is good for most houses but may need to be adjusted higher in some cases. Also you need to add a couple pounds pressure over the minimum just for safety.

So for your problem, make sure that the bleed valve on that top radiator is not plugged and then I would turn the PRV adjusting screw to add a little more pressure and then go to that radiator and try to bleed it. When you get the radiator to bleed out the air and get water out then you are at the minimum pressure needed to fill your system. hope this helps
Old 12-10-20, 08:10 AM
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A good starting point for jbct9 would be verify boiler water pressure. The original gauges are often way off and should be verified. Here are old DIY links on subject

Along with gauge on boiler, I have second 4" one near regulator that is more accurate and easy to read when checking or adjusting.
Old 12-10-20, 03:45 PM
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I agree with Steamboy. Your pressure is too low. Jack up the pressure to, say, 15psig.

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