I found this by accident, we are looking at a slab floor with carpet and a carpet pad installed. The A/C unit was operating as indicated by the blue floor register. What are we looking at.
BTW this was a first for me and before you ask the water meter was not rotating;-)
Show me what ya got:D
A crack in the slab?
Yip sure enough but why the higher temp that ground beneath the slab is colder this time of year
Cool, I would have guessed that the ground was warmer,
(I don’t do IR) but does it have something to do with the delta T?
The ground is warmer than the AC at the registers?
Water leak under slab.
Ya got that right but the water meter was not rotating 
Was the water from an exterior source? Thanks for you expertise with IR and Home Inspections.
could it have been a Bath/Kitchen coupling not glued correctly drain with a slow leak.
I have no way of knowing for sure on a visual inspection but my thinking is there is a drain line leak beneath the slab and a big one. The water showed up in four different cracks in the slab all in different rooms and with all the water in the home shut off the meter was not rotating. We ran a lot of water down the drains before it showed up in the floor cracks and we would have missed this totally if not for IR because water never penetrated the top side of the carpet we would have never known by just stepping on the carpet.
Thank goodness for IR we will get another 10 inspections in referrals because of this find.
Thanks Charley Love your posts we all can improve our knowledge with help like this and other posts .
Much appreciated .
My first observation is that this is an air, not a water leak.
Location.
Orientation.
Pattern.
You had the heat on at some point.
2nd, Even if the heat source is from water, the pattern is from the transmittance of air under the slab.
Ya would be wrong not only wrong but dead wrong. Whats the first rule of IR (always confirm your IR with a moisture meter) and we did the moisture meter was in the red. We actually slipped our arm beneath the carpet at the floor register and could feel the moisture.
Not my first Rodeo;-)
This is of special concern with slab homes, especially down your way during recent small earthquakes.
My first rule of IR is not to rely on any device that does not measure what your looking for…
I gave you my observations, based upon what you provided. You didn’t (and still have not) demonstrated to me that this is about a “water leak”. You didn’t say you were using a moisture meter either. So that doesn’t help my observation. But in spite of that…
Using a moisture meter, you measured conductivity. Yes, moisture does increase conductivity but it does not necessarily say “water”.
Yes, your meter went into “the red zone” but not sufficient enough to show “water”.
Second, the thermal exception does not indicate moisture. At least not the way you have the thermal image tuned and focused.
I am rather surprised with your assumption based upon your background in HVAC. Condensation from an HVAC supply air register does not occur because there is water leaking in the HVAC system. It occurs due to condensation.
Heat consist of sensible heat and latent heat. Latent heat = moisture. When this high temperature moisture laden air comes in contact with temperatures below the dew point moisture occurs. Are you sure you’re not measuring condensation?
What is below a concrete slab in all cases? Moisture. The crack as the conduit to bring it indoors.
In your first thermal scan IR_16734, I see warm air coming from the right supply air register.
IR_16742: does this anomaly pattern indicate moisture or air? I call it air.
What would cause a crack in the concrete floor? Sub slab HVAC conduit?
I am not debating your conclusion. As I stated:
What I am pointing out is not to be “tunnel visioned” in this business. Until you prove otherwise, there are always other options.
You eliminated option #1 by looking at the water meter. This shows that there is no cold water entering the house that could be associated with a hot water line leak.
Our next assumption is that the water from the sanitary drain use during the inspection caused this to occur. Did you in fact scan the floor before and after operating the hot water? If you did not, you cannot identify the source as being caused by your inspection testing.
In thermal image IR_16744, the supply air register is hot with reference to the indoor air conditions. This scan was taken after the air conditioner was running. This shows an air connection sub slab to the HVAC supply air conduit. If hot air is leaking into the ducts, will it not also leak out of the duct when the unit is operating? Is this not about air transmittance?
Current home inspection conditions:
Outdoor ambient conditions at the time of your inspection were below the indoor air temperatures indicating that the heat was on at some point during your analysis.
Relative humidity of the outdoor air was 84% relative humidity. Dew point temperature was 60F. This equates to moisture not being conducted from the outdoor air. This concludes that the source of moisture probably originates below the concrete slab.
Also we must consider building pressurization-depressurization as the source of causing a thermal bypass between the concrete slab and the interior.
So to reassess my initial observation; I stand by my assessment that this is air transmittance between the slab and the interior of the space. The source of the heat is below slab and has multiple potential sources. Though there is a high probability of the heat source being associated with hot water 120°F entering the sub slab area creating a 75°F thermal anomaly below the carpet of the floor, what we’re looking at above the carpet is not directly connected to the water leak as a water induced anomaly. This much heat would cause an uneven pattern in the concrete slab near its source. This was never identified or disclosed. We can see footprints on the carpet on numerous thermal scans indicating that the thermal imager is capable of very small amounts of heat transfer under these conditions.
It is our job as thermographer’s to present all of the potential causes for the situations we have identified (not just one, based upon a conductive moisture detection device).
When they jackhammer the floor up in this house and they find that there is not a water leak, what do you suppose your next telephone conversation will concern? What happens when David A. Andersen and Associates shows up and pressurizes your sewer line and finds there is no leak, then conducts a duct blaster test which indicates a 280 CFM air leak sub slab.?
So there you have it boys and girls. Two level III thermographer’s with a difference of observation based upon similar experience, training and appropriate equipment. Now let’s throw in a FLIR One into this equation and see where it takes us!
This is not Charley’s first Rodeo, but it doesn’t mean he won’t get thrown off some time…
I also have the scars from being thrown, just like him! 
And fracking…
David David David your troubling shooting this from the internet and a thermal image is like trying to repair an A/C unit over the telephone. I was on site and your in Tenn big difference my friend.
This home was vacant for weeks. The A/C unit was operated for approximately 10 minutes before I found those cracks and yes we did operate the A/C unit and the furnace at different times while taking those images. The A/C unit made no condensate so that blows that theory out of the water.
We had a ton of hot water running down the drains right before these images were taken. My son had turned on the hot water to make the water heater fire so I could run a draft test on the WH and he got side tracked and left the HW running longer than normal That is basically how we found the water under the slab.
Yo David it helps to be on site and have the big picture in front of you;-)
Exactly. I am only giving my opine on what I see and the information given.
Not saying what it is, just giving my asked for opinion.
I just don’t see the water. Just my opinion from my observations.
I’m confident that the hot water is the heat source, just not the exception.
You know better because you were there. But all things must be considered.
Good find. Good follow-up for what you were there for.
But caution on what is/is not an absolute.
You do not need water to have moisture.
You two should do this more often It’s a great learning experience for all of us.
Great post Charlie!
I appreciate the information from both you and David.
My apologies Charley… not Charlie.
