Dear Gents,

What are your experience in detecting leaks of water, for example in pipes in houses with airbone / structure bone ultrasound?

I know that water is not a gas, so its viscosity generates less ultrasound and turbulence than compressed air for example. I am talking about detecting internal leaks of course. What could be the lowest level of leak to detect? Perhaps, other Pdm techniques as Termography would be more effective or Pressure decay for example?

Regards,
Allen

Anyone wanting to find water leaks with ultrasound should first try sonic sound (low-frequency) first. Water leaks is best heard with the low-frequency and not high frequency. I wrote an article in UPTIME Magazine last April about underground leak detection. Air is the key. No matter if it is copper, galvinized, or plastic pipes you will need to pressurize the leak and scan for the leak. Using a nitrogen bottle of compressed gas at 20-30 psig should cause the water in the pipe to make enough noise for you to hear. The low-frequency unit acts as a "Ground Microphone" and you simply zero in on the leak.
I own an underground leak detection business in Atlanta, GA. I have 18 years of ultrasound for pdm and years as a plumber. The attached article is what you need to know.
Starting this next year in February in Atlanta, GA we will be holding an Underground Leak and Pipe Locating Class.
You may want to get UPTIME Magazine to send you a copy of the UPTIME APRIL 2006 Magazine.

April_UPTIME_Article_revision.4MAINTFORUM.doc (72 Kb, 41 downloads) Underground Leak Article

Thanks Jim,
It is a fantastic article. What about domestic applications? In those cases I suppose you would need to use some contact probe mostly, instead of using airbone ultrasound probe. Other issue would be the difficult to pressurize pipes in a house for example.
On the other hand, how could you explain that a water leak could generate sonic sound not ultrasound? Is it something that we could generalize for any application with water?
Regards,
Allen

It doesn't matter domestic, or Residential, Commercial and Industrial. Low-Frequency is best. Its when you spent a lot of time using low-frequency and still not found the leak, you may take high-frequency out of the closet and use it. Drive steel stakes (5-7 stakes) into the ground close to the pipe spacing about 20 feet apart. Any suspect sound should be treated as a leak and the stakes are then moved closer together, then with the contact probe you touch the stakes, the stake with the highest reading is where you center on. Ultrasound is short wave, you will probably only hear a distance of 18 inches at 5-6 feet down. Now I will use high-frequency as I mentioned to go into a residential home and touch the line or valves under the sink provided they are metallic. If they are not forget it!
With either system, Low or high you are always using a "contact probe". The low-frequency microphone is metallic disc with a transducer built atop of it. The disc is plopped on the concrete, or floor. If you are outside the home in common ground you use a set of long rods screwed together and then (screwed onto) attached to the ground microphone you probe the ground by pushing the rods into the dirt, etc...
(your last paragraph) Its not that ultrasound is not generated its that when water surrounds a pipe if the pipe is plastic there is virtually NO noise! If the pipe is metallic it makes some noise. If you turn-off the water system for several hours or days the water will be obsorbed into the ground and the area around the pipe should be a cavity of sorts and as air is pumped into the pipe the what you will hear very distinctly is the sound of air & water escaping from the pipe...Sounds transmitting through the ground is heard by the lower-frequency better, longer wave length, more power, better chance of hearing it.
Later.

Hi Jim,

Have you got some web or pdf to show me the kind of equipment of detection of sound you are talking to?
Could you please indicate me if there are some proof I could make to try the ability of detection of the equipment?
I work for a company which sells ultrasound equipment and customer has asked to us some quotation to detect water leaks in domestic application; what would be you opinion about this issue? what would you do? Which some technical consideration you would make in the proposal?
Regards,
Allen_Forum