Central heating leak part 2

[Gattopardo]

So after putting in the monument drain dye, buying a UV torch, there doesn't seem any visible leaks around the radiators or associated visible pipework nor down the waste pipe from the condensate. So the next trick I think about.  I have a digital non contact thermometer things.  Decided that there are warm spots from the pipes in the concrete, these hot spots should be of a uniform temperature.  So decided to track the pipes and see it there is a significant temperature differential which means that something is a miss.

Found an area that has a significant raised temperature in a localised 10cm area that coincides with a 90 degree pipe joint.  I noted that the cats had been sitting in that area.  Now I know why.

So do I get the kango out and excavate the area?

[Aunt Maud]

You could try a moisture meter on the area first and compare it to the reading from another area of the floor.

[PaulF]

Dust off and nuke the site from orbit, it's the only way to be sure

Seriously does sound like the only option

[Canardly]

Certainly sounds like it.

[Brucey]

a note of caution; the heat transfer rate from the fluid through the wall of the pipe will vary with the flow conditions and the material surrounding/in contact with the pipe.

It is possible that the flow is changed by travelling around a 90 degree bend such that the heat transfer into the surrounds is increased. If there is damp material in contact with the pipe at that point, the rate of heat transfer out of the pipe will also be increased.

However in the absence of a better idea, or a leak that is more obvious somewhere else, you are maybe going to have to bite the bullet and start to dig stuff up sooner or later.

BTW do you think the leak is such that you would be able to hear it/find it etc, if the system was drained down and a slight overpressure of air was used?

Also, is it worth trying a sealant in the system? Fernox make one.  Even if this worked well enough to get you through the winter, it would allow the repair to be delayed until it is more convenient....?

cheers