water pressure test result questons

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Old 09-26-14, 06:06 AM
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water pressure test result questons

I am installing a 16' section CI baseboard with a 90 degree turn on my first floor. It is in place and pipes go down to basement and ready to connect to the main line. I did water pressure test yesterday. I have purged all air out. The water pressure was 62psi and then I closed the water loop and separated it from water supply. I checked all joints and low points. No leakage was found.

This morning the pressure is down to about 43psi. I checked all the connections and low points again. All are dry. I checked several times with my dry figures.

I am wondering why the pressure goes down without air inside? Is this normal? Does this test pass or fail? Is this because there are still some air inside?
 
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Old 09-26-14, 06:44 AM
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Yes there probably still some air inside that escaped and thus the drop in pressure.
 
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Old 09-26-14, 07:51 AM
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If air can escape, typically so can water...

Did the temperature of the water and the building remain the same?
 
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Old 09-26-14, 07:55 AM
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20 psi is a lot and more than I would think possible for a temperature change. A few degrees could be from temperature but 20 makes me suspect a slow leak somewhere.
 
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Old 09-26-14, 08:18 AM
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Me too Dane, if he started with cool/cold water... I didn't quantify ... was just sayin' that temp change needs to be monitored along with pressure change in order to get a meaningful test. Ideally the volume of water would also be known.

Besides, if he filled with cold water, and the building is warmer, wouldn't the pressure go UP?

On the other hand, if he filled with warm/hot water, I would absolutely expect a 20 PSI change as it cooled.

Go ahead and try it yourself. Fire your system up to say 100F and remove (valve off) the expansion tank. When that system cools, the pressure will sink like a stone.
 
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