slow leak on CI baseboard (water heating) air pressure testing

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Old 09-23-14, 09:26 AM
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slow leak on CI baseboard (water heating) air pressure testing

I am installing #9 CI baseboard in one of my rooms. There are four sections in this big room. Three of them are longer than 10 feet. I did air pressure test on all of them with air vent installed. There is a slow leak on one of them. I can see the leakage is from the air vent with soapy water. The pressure dropped from 30 to 25psi in one hour. Doesn't matter how tight I turn the air vent, there is always a little. Is that small leakage will be ok when water is connected?

The air vent comes with the CI baseboard. It is not the automatic air vent type. I changed the air vent. It seems both of them are not good enough. But they may be good enough for water?
 
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Old 09-23-14, 09:30 AM
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You mean a manual bleeder?? If so, no it should not leak.

 
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Old 09-23-14, 09:40 AM
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yes, so I should put another one. I will try again.

Small air leak will indicate water leak later?
 
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Old 09-23-14, 10:47 AM
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Small air leak will indicate water leak later?
Yes........................................................

How many psi are you pumping them up to?????
 
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Old 09-23-14, 06:32 PM
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the air pressure is 30psi
 
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Old 09-24-14, 07:34 AM
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Replace the bleeder. If it leaks with air, it will leak with water.

Testing with air pressure is potentially dangerous and not recommended - because of the large amount of stored energy, any part that gives away can become a lethal missile. And, 30 psi is too high, in any case - you risk lifting the relief valve and are at the maximum design operating pressure of the boiler. What if the boiler decides to split open?

Plumbers sometimes leak test with a low pressure of nitrogen over night to see if the small static pressure goes down. What you are doing is not a good practice.
 
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Old 09-24-14, 07:46 AM
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Agree with the dangers of air testing.

Another point to be made is that TEMPERATURE changes are going to also affect the pressure over time. Testing with water also suffers from temp changes though... expansion and contraction of the medium with temperature is going to affect the pressure.

So it's something to keep in mind when assessing the gauges after a night of sitting. Is the environment cooler or hotter than it was?
 
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Old 09-24-14, 08:08 PM
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Thank you guys. I will change to water to see if there is any leak before connect them onto the main line.
 
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