leak testing copper piping project

[fozzy12]

I've constructed a radiant heating system distribution panel for my garage. I purchased some of the pieces prebuilt, I've connected and fabricated the rest of the stuff. I'm comfortable sweating copper. The company provided a valve stem fitting so that I can pressurize the system to make sure it's tight. The tubing and the slab manifold are tight, no leaks. The rest of the system sans the second floor tubing is what I'm testing. I found 2 small leaks with soapy water solution and fixed them. I still can't get the thing to hold 30 psi for more than a couple of hours. Does anyone have any other way of checking this? I'm sure there has to be a very small leak somewhere but I'll be darned if I can find it.

Any help would be appreciated. I don't want to put water in it until I'm absolutely sure it's tight. The heat source is a 75 gallon Brad White water heater, which is also being pressure tested as part of the system.

Thanks
Eric

[jadnashua]

Snug up any packing nuts of any valves in the system and see if that makes a difference. The normal pressure of a hydronic system is usually only in the 12-18 psi range, and an air leak at 30, may not be a water leak at a lower pressure. Best to find it, though.

[Redwood]

When I look for leaks in an air test I use an ultrasonic leak detector...
On high sensitivity it picks them up about 20' away.

[fozzy12]

Redwood,
Who sells those and how much do they cost?

Thanks!

Eric

[kingsotall]

Don't know the cost but the ones I've seen in use definitely were a pretty penny. I'm thinking couple grand.

[jadnashua]

Did a quick search on ultrasonic leak detectors...http://www.testersandtools.com/Amprobe-ULD-300-Ultrasonic-Gas-Leak-Detector.php?page=product&Department=18&Category=1&product=QVT-2007020711360385083 is a couple hundred dollars. Most cost more, but probably do more. Add a transmitter, and you can then check for leaks on things like doors, refrigerators, etc...you put the transmitter inside then close the door and look for leaks with the detector. Fancy ones are in the thousands.

[Redwood]

The one I have was a couple 3 hundred bucks.
I had a job at a factory fixing compressed air leaks.
It paid for itself first time out!
A lot of the pipes were overhead and walking around on the floor below I could detect leaks 20' up in the air. I had to lower the sensitivity to pinpoint them and get close but I had to tag all the leaks for repair anyway.
But the only time I had to get into an area with the lift was when a leak was indicated from the floor.
When compressed air leaks out of a pipe it creates a non linear flow which is what the ultrasonic tester detects.

Look see here... #8402T55
http://www.mcmaster.com/#catalog/114/2175