Please help. Inside wall is dry. But every time I run the kitchen sink tap water, there is generous amount of water leaking outside to my brick wall which is right behind the sink on to the slab.

I had a repair man came in, he cut out the inside wall behind the sink and it was dry. He replaced the water hose and the said it was the water sipping from the hose. I was not convinced, because the water hose was also dry, but he said there were minerals deposits on the outside of the hose, which indicated the leak. I paid the $200, and the problem appeared to be fixed for several days. Now it came back.
I don't want to call the plumber back, as I no longer have confident in him, and if the brick wall has to be tear down, I afraid he will want more money.

I did some search on the internet about repair brick wall, I found recommendations to get a masonry, instead of do it yourself. Now I'm not sure if I should call the masonry first, or the plumber first.

Anyone has any idea what it is? Or have similar problems? The house in one floor, build on a slab. It is about 50-60 years old. This is the only leak That we known of.

Could be the drain side. Even with valves off, the line pressure would probably shown a leak. Corrosion is a fairly typical indication of a leak but not always. Do this. Pour water down the drain after getting water from another source, not the sink. Fill up a pail from the tub and pour it down the sink drain. Tell us what you find out.