Embedded Copper tube repair Method

[BijuVyttila]

Hello all,
We have a 1” diameter copper (ASTM B88 Type K) line embedded in mass concrete that is part of a Piezometer system that is not holding pressure in a hydro dam project.
Prior to concrete placement it was tested and held a test pr of 290psi, but post concrete placement the pressure quickly falls to 125psi, then gradually to 0.
Total length is about 30 meters, with 6 nos of 1" elbows - so we are expecting the leak somewhere around first 15 meters.
As this is embedded no way knowing where the leaks are - so looking for an expertise, suggestions or experience in dealing such situation

 

[Ron]

Corrosion! You probably have corrosion in the tubes which is causing the pressure drop. Try using a borescope to view the inside of the pipe to check for this. Embedding copper in concrete is not a great idea.

 

[BijuVyttila]

Hi Ron - it is new construction, just installed. Yes we are getting a boroscope to check inside.

 

[EdStainless]

If it is mechanical damage installing a plastic lining may be your best option.

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P.E. Metallurgy, Plymouth Tube

 

[jdonville]

I'm guessing that during concrete placement or curing, (at least) one of the joints and/or the bottom cap came loose.

What pressure range is actually required for the use of the piezometer system? Water exerts a pressure of ~0.43 lb/in2 per foot of static pressure, so even 100ft (~30m) of head should only need to resist ~43 psi, and I would expect the concrete surrounding the pipe to provide that easily.

I would at least look into the cost to abandon the pipe and install another instrument to compare against the potential cost of rehabilitation/repair measures.