hot water leaking under a slab
I have a 17 year old ranch slabber with a hot water leak under the slab. I conducted a test: the valve from the meter to the house service open; a separate valve to the hot water open; no faucets in the house open and the water meter still moves. The valve from the meter open; the valve to the hot water service closed; no faucets open and there was no movement on the water meter. I concluded that there must be a leak somewhere in the hot water lines embedded in the slab, but (thankfully) not the cold water lines. I have no evident damp spots anywhere in the house so I think it must be leaking under the slab. Right now we are dealing with the problem by leaving the hot water service to the house off until hot water is required for showers, clothes washer or dishwasher.
I have been told by a couple of plumbers I have contacted that there are 2 avenues of repair I can pursue:
1. Locate the leak (which could be problematic since there is no apparent evidence of a leak), chip the concrete from around the leak to expose the copper and repair the existing pipe, then patch the slab. This on the face seems the route to go, but what if I fix one leak, and it turns out that it was not the only one? Is there any way to determine before hand if more than one leak exists? Also, what if the leak happens to be right under a load bearing wall? Will that complicate things?
2. The other solution I was given is to replace the existing hot water service by fishing new pex-tubing through the attic to all of the existing hot water outlets and sealing the current hot water pipes in the slab. I have some concerns about this however. I'm not sure I like the idea of having water service through the attic because of possible freezing and rupturing the pex and in the long run the additional cost to repair the damage. Another concern I have is will this method raise any flags with a home inspector if I decide to sell the house in the future or will this method affect the value of the home?
I know that without more information it would be hard to predict, but as far as expense is concerned does anybody have a clue as to which might be least expensive?
HELP!!! I'm really beyond the knowledge that I have in dealing with this problem and can use any advice that I can get. thanks!