I've noticed for several months that the water pressure to my shower is low and when I flush the toilet it is also slow. I complained to the water department and they checked and said I didn't have any leaks. Recently there's been water accumulating in my basement floor and now I hear the sound of water running at the main pipe. The water department turned off the water from the curb and the sound stops. When it is turned back on the sounds returns. The water dept says that I have a leak before the meter in the pipes and a plumber says that he is 99% sure that there is a leak somewhere in the ground (I pray not). What should be my concerns especially as far as cost. Even though the running water is not costing me anything through the water dept, I have to wet vac water every evening. I suppose I will have to get it fixed. What do you think will most lookly be the cost to fix?

The main pipe you hear water running,is it the drain you are hearing it run,or the H20 line

It sounds like to me it is a leak in the wall/ceiling,from you saying that H20 is on basement floor?

It is not the drain. I hear it running at the main H2O pipe. I also notice a louder sound when a toilet is flushed. It has been very humid and the pipes are cold and sweaty.

That you can hear a leak/water running and not be paying for the water is a surprise. If there is a leak BEFORE the meter, the water dept should fix it, AFTER the meter is your issue. With water in your basement(?) you have a wall leak or a leak from above that is running down the wall.