How do I do if sea leak at the rear walls? I live in an ancient house, and recently, I have the pipes...

I live in an ancient house, and recently, I have the pipes in the attic changed. However, starting after the pipes be changed, the water meter very soon runs even though there is no marine being used contained by the house. I am inclined to believe that there must be leaching in the pipes inside the walls cause by all the work man done in the attic. What is the best opening to check for leakage contained by the walls?
Answers:    it there be leakage within the walls you would see water coming out somewhere.... If within is a shut off stopcock between the meter and the house close it and see if the meter is still turning..that would mean the trickle is underground.(if there isn't a stopcock it would not be too hard to include one, which is a good model anyway...)
It would be best to not use theory but evidence! Look at the toilets within your home is the water staying within the tank after they flush or do they keep hold of dribbling water into the bowl? Are the fausets leak? washer connection lealing. Good luck