Hand-held "Water Detector" device for cinderblock wall

I received an estimate today from a waterproof company regarding a moisture seepage issue, and one of the things this person did was bring a hand-held "water detector" with two metal prongs. He pressed the prongs of the device against the cinderblocks and it started making beeping noises to indicate that there is currently "water in the wall". Is this device a gimmick or is it a legitimate means of determining that a wall "has water in it." When I tried the device on a rock, which was obviously dry, the device did not go off. Likely the device was detecting some moisture but I suspect that is programmed to be hyper-sensitive to any degree of moisture.
Granted, I don't doubt that my wall has a moisture seepage issue during rainy weather (or possibly if the sprinklers were on that day). I'm just wondering if the device itself has any real value in determining the extent of the problem, or is this just a "stage prop" for them to be able to say "AHA, you do, in fact have a problem here, because this device says so".
J.
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jay wrote:

to locate dampness sources in drywall, concrete, wood, etc.
http://testproducts.com/safecart/index.php/cPath/33/?source=Google for some varieties.
Interpreting results in a concrete block wall can be tricky since almost all basement walls will have some moisture.
Jim
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It is a legitimate tool. Mine is called a wood moisture meter. It has pins and a pinless mode that detects reflection of low frequency radio waves to find moisture without marking walls and floors. Mine cost about $500.00 and measures wood moisture from 6% to 99%. 100% wood moisture means the wood has as much water as wood (50/50). I have seen meters that cost from $200 to $1,000, depending on the features and sensitivity. Some are calibrated only for wood, some are also calibrated for masonry.
Stretch
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Thanks.
By the way, funny, but this person, assuming I heard him correctly, at one point, told me that he guesses that my wall probably has 200 gallons worth of water trapped within it. He's not claiming that the meter tells him that. Is there any reason to estimate that a cinderblock wall (45 feet long) could really be holding that much water? I don't doubt that there is moisture in the wall. I just doubt that we're talking huge quantities of water. Could this really be true, or a bunch of hype? (hasn't rained for a week or two, and I've never had any puddles on the basement floor, yet)
J.
<<Interpreting results in a concrete block wall can be tricky since almost all basement walls will have some moisture.>>
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Jay, It depends on the area and thickness of the wall and the percentage of moisture. Then do the calculations. 8.33 pounds per gallon of watter at 70 degrees F.
Stretch
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That wall consists of approximately 400 concrete blocks (assuming the standard 8x8x16 block, and an 8-foot-high wall). Is there, on average, half a gallon of water in each one? I kinda doubt it....
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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the water gets trapped in the cavities in the cinderblocks
assumming you have a french drain and sump pump....or another way to deal with the water ....
drill 2 small holes at the bottom of the wall of each block and the water will drain out
then paint the blocks with dry lock paint.
the wall will stay dry after that but you need a sump pump and french drain to deal with the water that will drain from the holes that you drilled
Mark
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